Himalayas

Abstract A spur of ancient rocks partly covered by gently-dipping Tertiary beds extends from the Shillong Plateau and Mikir Hills north-eastwards beneath the alluvium of Upper Assam. Over this spur the Eastern Himalaya have been thrust southwards and the Naga Hills have been thrust north-westwards. The amount of movement of the overthrust masses cannot be determined but it is suggested that in each case the total displacement may be 150-300 kilometres or even more. The Shillong Plateau is separated from the Surma Valley by a faulted monocline with southerly dips. This fault, the Dauki tear-fault, is now shown to have a probable horizontal displacement of about 250 kilometres, and thus to be a major feature of the tectonic pattern of the Indian sub-continent. The horizontal movement along the Dauki tear-fault detached the Shillong Plateau from the main mass of the Indian Shield. The principal movements occurred late in the Tertiary, mostly in the Pliocene.

@article{doi1017491jgsi1964050111,
    author = "Evans, Paul D.",
    title = "The Tectonic Framework of Assam",
    year = "1964",
    journal = "Journal of the Geological Society of India",
    abstract = "Abstract A spur of ancient rocks partly covered by gently-dipping Tertiary beds extends from the Shillong Plateau and Mikir Hills north-eastwards beneath the alluvium of Upper Assam. Over this spur the Eastern Himalaya have been thrust southwards and the Naga Hills have been thrust north-westwards. The amount of movement of the overthrust masses cannot be determined but it is suggested that in each case the total displacement may be 150-300 kilometres or even more. The Shillong Plateau is separated from the Surma Valley by a faulted monocline with southerly dips. This fault, the Dauki tear-fault, is now shown to have a probable horizontal displacement of about 250 kilometres, and thus to be a major feature of the tectonic pattern of the Indian sub-continent. The horizontal movement along the Dauki tear-fault detached the Shillong Plateau from the main mass of the Indian Shield. The principal movements occurred late in the Tertiary, mostly in the Pliocene.",
    url = "https://doi.org/10.17491/jgsi/1964/050111",
    doi = "10.17491/jgsi/1964/050111",
    openalex = "W2320083195"
}

ABSTRACT Just beyond the western boundary of West Bengal, the great Indian shield disappears below a blanket of alluvium. The exposed part of the shield bordering the Bengal basin is marked by a row of intracratonic Gondwana basins, a series of thrust zones in Singhbhum, and extensive exposure of basic volcanics in the Rajmahal Hills. Intensive geophysical surveys and deep drilling in the alluvium-covered plains of West Bengal have revealed a thick section of Cretaceous and Tertiary sediments lying on a basement of basalt lava flows, presumably of the same age as the Rajmahal Group volcanics. An extension of the easternmost Gondwana basin farther east, below the Bengal alluvium, also is suggested. A series of buried basement ridges, marking the western margin of the Bengal basin, presumably kept the Gondwana continental basins isolated from the main Bengal basin through most of Tertiary time. Locally, during the late Tertiary, the sea transgressed over these basement ridges and onlapped parts of the Indian shield. Flanking the eastern margin of the buried ridges is a row of basin-margin en échelon faults and scarps, possibly the shallower expressions of some deep-seated movements in the basement. East of this marginal fault zone lies the stable shelf of West Bengal with a homoclinal dip toward the southeast. Seven seismic reflectors mapped in the Mesozoic and Tertiary sediments of the shelf indicate uniform increase of thickness (3,000 to 27,000 feet, approximately) of these sediments toward the southeast. Except for a few normal faults, the area is practically undisturbed structurally. An extensive unconformity between the Miocene and Pliocene has been recognized. Locally, weak evidence of another depositional break, at the top of the Oligocene, is present. Around Calcutta, the Eocene key horizon (Sylhet Limestone) shows a conspicuous basinward flexure (the “hinge zone”) at a depth of about 15,500 feet. East of this “hinge,” which traverses the whole Bengal basin, lies the deeper part of the basin with a greater rate of subsidence and a different lithofacies. Seismic interpretation suggests a sharp lithofacies change at this zone, from the Eocene nummulitic limestone of the stable shelf to a thick sequence of clay and shale in the deeper part of the basin. In the younger Tertiary sediments is a similar change of facies from the arenaceous sediments of the stable shelf to the dominantly argillaceous sediments downdip. Marine transgression on the West Bengal shelf occurred during the Late Cretaceous (locally), late Eocene (extensively), and Miocene (in the eastern parts only). Except for these periods of marine transgression, sedimentation took place under fresh-water, estuarine, or deltaic conditions. A summary of the tectonic and depositional history of the whole region, from the eastern margin of the Indian shield to the folded belt in Assam, is given in conclusion. This integrates the work done in West Bengal by the Indo-Stanvac Petroleum Project with that done in Assam by the Burmah Oil Company and its affiliates.

@article{doi1013065d25b60b16c111d78645000102c1865d,
    author = "Sengupta, Supriya",
    title = "Geological and Geophysical Studies in Western Part of Bengal Basin, India",
    year = "1966",
    journal = "AAPG Bulletin",
    abstract = "ABSTRACT Just beyond the western boundary of West Bengal, the great Indian shield disappears below a blanket of alluvium. The exposed part of the shield bordering the Bengal basin is marked by a row of intracratonic Gondwana basins, a series of thrust zones in Singhbhum, and extensive exposure of basic volcanics in the Rajmahal Hills. Intensive geophysical surveys and deep drilling in the alluvium-covered plains of West Bengal have revealed a thick section of Cretaceous and Tertiary sediments lying on a basement of basalt lava flows, presumably of the same age as the Rajmahal Group volcanics. An extension of the easternmost Gondwana basin farther east, below the Bengal alluvium, also is suggested. A series of buried basement ridges, marking the western margin of the Bengal basin, presumably kept the Gondwana continental basins isolated from the main Bengal basin through most of Tertiary time. Locally, during the late Tertiary, the sea transgressed over these basement ridges and onlapped parts of the Indian shield. Flanking the eastern margin of the buried ridges is a row of basin-margin en échelon faults and scarps, possibly the shallower expressions of some deep-seated movements in the basement. East of this marginal fault zone lies the stable shelf of West Bengal with a homoclinal dip toward the southeast. Seven seismic reflectors mapped in the Mesozoic and Tertiary sediments of the shelf indicate uniform increase of thickness (3,000 to 27,000 feet, approximately) of these sediments toward the southeast. Except for a few normal faults, the area is practically undisturbed structurally. An extensive unconformity between the Miocene and Pliocene has been recognized. Locally, weak evidence of another depositional break, at the top of the Oligocene, is present. Around Calcutta, the Eocene key horizon (Sylhet Limestone) shows a conspicuous basinward flexure (the “hinge zone”) at a depth of about 15,500 feet. East of this “hinge,” which traverses the whole Bengal basin, lies the deeper part of the basin with a greater rate of subsidence and a different lithofacies. Seismic interpretation suggests a sharp lithofacies change at this zone, from the Eocene nummulitic limestone of the stable shelf to a thick sequence of clay and shale in the deeper part of the basin. In the younger Tertiary sediments is a similar change of facies from the arenaceous sediments of the stable shelf to the dominantly argillaceous sediments downdip. Marine transgression on the West Bengal shelf occurred during the Late Cretaceous (locally), late Eocene (extensively), and Miocene (in the eastern parts only). Except for these periods of marine transgression, sedimentation took place under fresh-water, estuarine, or deltaic conditions. A summary of the tectonic and depositional history of the whole region, from the eastern margin of the Indian shield to the folded belt in Assam, is given in conclusion. This integrates the work done in West Bengal by the Indo-Stanvac Petroleum Project with that done in Assam by the Burmah Oil Company and its affiliates.",
    url = "https://doi.org/10.1306/5d25b60b-16c1-11d7-8645000102c1865d",
    doi = "10.1306/5d25b60b-16c1-11d7-8645000102c1865d",
    openalex = "W1993783239"
}

A comprehensive study of the observations of seismology provides widely based strong support for the new global tectonics which is founded on the hypotheses of continental drift, sea-floor spreading, transform faults, and underthrusting of the lithosphere at island arcs. Although further developments will be required to explain certain part of the seismological data, at present within the entire field of seismology there appear to be no serious obstacles to the new tectonics. Seismic phenomena are generally explained as the result of interactions and other processes at or near the edges of a few large mobile plates of lithosphere that spread apart at the ocean ridges where new surficial materials arise, slide past one another along the large strike-slip faults, and converge at the island arcs and arc-like structures where surficial materials descend. Study of world seismicity shows that most earthquakes are confined to narrow continuous belts that bound large stable areas. In the zones of divergence and strike-slip motion, the activity is moderate and shallow and consistent with the transform fault hypothesis; in the zones of convergence, activity is normally at shallow depths and includes intermediate and deep shocks that grossly define the present configuration of the down-going slabs of lithosphere. Seismic data on focal mechanisms give the relative direction of motion of adjoining plates of lithosphere throughout the active belts. The focal mechanisms of about a hundred widely distributed shocks give relative motions that agree remarkably well with Le Pichon's simplified model in which relative motions of six large, rigid blocks of lithosphere covering the entire earth were determined from magnetic and topographic data associated with the zones of divergence. In the zones of convergence the seismic data provide the only geophysical information on such movements. Two principal types of mechanisms are found for shallow earthquakes in island arcs: The extremely active zone of seismicity under the inner margin of the ocean trench is characterized by a predominance of thrust faulting, which is interpreted as the relative motion of two converging plates of lithosphere; a less active zone in the trench and on the outer wall of the trench is characterized by normal faulting and is thought to be a surficial manifestation of the abrupt bending of the down-going slab of lithosphere. Graben-like structures along the outer walls of trenches may provide a mechanism for including and transporting sediments to depth in quantities that may be very significant petrologically. Large volumes of sediments beneath the inner slopes of many trenches may correspond, at least in part, to sediments scraped from the crust and deformed in the thrusting. Simple underthrusting typical of the main zone of shallow earthquakes in island arcs does not, in general, persist at great depth. The most striking regularity in the mechanisms of intermediate and deep earthquakes in several arcs is the tendency of the compressional axis to parallel the local dip of the seismic zone. These events appear to reflect stresses in the relatively strong slab of down-going lithosphere, whereas shearing deformations parallel to the motion of the slab are presumably accommodated by flow or creep in the adjoining ductile parts of the mantle. Several different methods yield average rates of underthrusting as high as 5 to 15 cm/yr for some of the more active arcs. These rates suggest that temperatures low enough to permit dehydration of hydrous minerals and hence shear fracture may persist even to depths of 700 km. The thickness of the seismic zone in a part of the Tonga arc where very precise hypocentral locations are available is less than about 20 km for a wide range of depths. Lateral variations in thickness of the lithosphere seem to occur, and in some areas the lithosphere may not include a significant thickness of the uppermost mantle. The lengths of the deep seismic zones appear to be a measure of the amount of under thrusting during about the last 10 m.y. Hence, these lengths constitute another ‘yardstick’ for investigations of global tectonics. The presence of volcanism, the generation of many tsunamis (seismic sea waves), and the frequency of occurrence of large earthquakes also seem to be related to underthrusting or rates of underthrusting in island arcs. Many island arcs exhibit a secondary maximum in activity which varies considerably in depth among the various arcs. These depths appear, however, to correlate with the rate of underthrusting, and the deep maxima appear to be located near the leading (bottom) part of the down-going slab. In some cases the down-going plates appear to be contorted, possibly because they are encountering a more resistant layer in the mantle. The interaction of plates of lithosphere appears to be more complex when all the plates involved are continents or pieces of continents than when at least one plate is an oceanic plate. The new global tectonics suggests new approaches to a variety of topics in seismology including earthquake prediction, the detection and accurate location of seismic events, and the general problem of earth structure.

@article{doi101029jb073i018p05855,
    author = "Isacks, Bryan L. and Oliver, Jack and Sykes, Lynn R.",
    title = "Seismology and the new global tectonics",
    year = "1968",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "A comprehensive study of the observations of seismology provides widely based strong support for the new global tectonics which is founded on the hypotheses of continental drift, sea-floor spreading, transform faults, and underthrusting of the lithosphere at island arcs. Although further developments will be required to explain certain part of the seismological data, at present within the entire field of seismology there appear to be no serious obstacles to the new tectonics. Seismic phenomena are generally explained as the result of interactions and other processes at or near the edges of a few large mobile plates of lithosphere that spread apart at the ocean ridges where new surficial materials arise, slide past one another along the large strike-slip faults, and converge at the island arcs and arc-like structures where surficial materials descend. Study of world seismicity shows that most earthquakes are confined to narrow continuous belts that bound large stable areas. In the zones of divergence and strike-slip motion, the activity is moderate and shallow and consistent with the transform fault hypothesis; in the zones of convergence, activity is normally at shallow depths and includes intermediate and deep shocks that grossly define the present configuration of the down-going slabs of lithosphere. Seismic data on focal mechanisms give the relative direction of motion of adjoining plates of lithosphere throughout the active belts. The focal mechanisms of about a hundred widely distributed shocks give relative motions that agree remarkably well with Le Pichon's simplified model in which relative motions of six large, rigid blocks of lithosphere covering the entire earth were determined from magnetic and topographic data associated with the zones of divergence. In the zones of convergence the seismic data provide the only geophysical information on such movements. Two principal types of mechanisms are found for shallow earthquakes in island arcs: The extremely active zone of seismicity under the inner margin of the ocean trench is characterized by a predominance of thrust faulting, which is interpreted as the relative motion of two converging plates of lithosphere; a less active zone in the trench and on the outer wall of the trench is characterized by normal faulting and is thought to be a surficial manifestation of the abrupt bending of the down-going slab of lithosphere. Graben-like structures along the outer walls of trenches may provide a mechanism for including and transporting sediments to depth in quantities that may be very significant petrologically. Large volumes of sediments beneath the inner slopes of many trenches may correspond, at least in part, to sediments scraped from the crust and deformed in the thrusting. Simple underthrusting typical of the main zone of shallow earthquakes in island arcs does not, in general, persist at great depth. The most striking regularity in the mechanisms of intermediate and deep earthquakes in several arcs is the tendency of the compressional axis to parallel the local dip of the seismic zone. These events appear to reflect stresses in the relatively strong slab of down-going lithosphere, whereas shearing deformations parallel to the motion of the slab are presumably accommodated by flow or creep in the adjoining ductile parts of the mantle. Several different methods yield average rates of underthrusting as high as 5 to 15 cm/yr for some of the more active arcs. These rates suggest that temperatures low enough to permit dehydration of hydrous minerals and hence shear fracture may persist even to depths of 700 km. The thickness of the seismic zone in a part of the Tonga arc where very precise hypocentral locations are available is less than about 20 km for a wide range of depths. Lateral variations in thickness of the lithosphere seem to occur, and in some areas the lithosphere may not include a significant thickness of the uppermost mantle. The lengths of the deep seismic zones appear to be a measure of the amount of under thrusting during about the last 10 m.y. Hence, these lengths constitute another ‘yardstick’ for investigations of global tectonics. The presence of volcanism, the generation of many tsunamis (seismic sea waves), and the frequency of occurrence of large earthquakes also seem to be related to underthrusting or rates of underthrusting in island arcs. Many island arcs exhibit a secondary maximum in activity which varies considerably in depth among the various arcs. These depths appear, however, to correlate with the rate of underthrusting, and the deep maxima appear to be located near the leading (bottom) part of the down-going slab. In some cases the down-going plates appear to be contorted, possibly because they are encountering a more resistant layer in the mantle. The interaction of plates of lithosphere appears to be more complex when all the plates involved are continents or pieces of continents than when at least one plate is an oceanic plate. The new global tectonics suggests new approaches to a variety of topics in seismology including earthquake prediction, the detection and accurate location of seismic events, and the general problem of earth structure.",
    url = "https://doi.org/10.1029/jb073i018p05855",
    doi = "10.1029/jb073i018p05855",
    openalex = "W2043546840",
    references = "doi101029jb073i006p01959, doi101029jb073i006p02119, doi101029jb073i012p03661, doi101029jz070i016p03965, doi101029jz072i008p02131, doi101038190854a0, doi101038199947a0, doi101038207343a0, doi1010382161276a0, doi101098rsta19650020, doi101126science15437531164, doi101126science15437551405, doi101130petrologic1962599, doi101785bssa0530010167, doi105408002213687121, sykes1967mechanism"
}

ABSTRACT The structural development of the Iranian ranges has certain peculiarities which contradict the conventional geosynclinal theory of mountain building. Early orogenic movements resulted in the consolidation of the Precambrian basement and the formation of a vast Iranian platform considered to be an extension of the Arabian shield. Only epeirogenic movements affected the region during the Paleozoic, which is represented by typical platform deposits. However, most of Iran went through all stages of a complete Alpine orogeny in spite of the prevailing platform character in preorogenic time. Important trends in the Alpine structural plan clearly were inherited from Precambrian structures. Precursory Alpine movements in Mesozoic time were strongest in Central Iran, although this region and the closely related Alborz (Elburz) Mountain area generally retained their epicontinental character, allowing for only a rudimentary geosynclinal development. More clearly geosynclinal conditions developed in peripheral fold belts: the Zagros, the Kopet Dagh, and the East Iranian ranges. Strong folding and thrusting during the Alpine orogeny proper in Late Cretaceous-Tertiary time affected most of Iran except the rigid Lut block in the eastern part of the country. The conventional tripartite division of Iran into an extensive median mass and two bordering ranges of geosynclinal origin (Zagros, Alborz) cannot be maintained. The writer replaces this oversimplified interpretation by recognizing the existence of more structural zones which differ in structural development and present tectonic style.

@article{doi1013065d25c4a516c111d78645000102c1865d,
    author = "Stöcklin, Jovan",
    title = "Structural History and Tectonics of Iran: A Review",
    year = "1968",
    journal = "AAPG Bulletin",
    abstract = "ABSTRACT The structural development of the Iranian ranges has certain peculiarities which contradict the conventional geosynclinal theory of mountain building. Early orogenic movements resulted in the consolidation of the Precambrian basement and the formation of a vast Iranian platform considered to be an extension of the Arabian shield. Only epeirogenic movements affected the region during the Paleozoic, which is represented by typical platform deposits. However, most of Iran went through all stages of a complete Alpine orogeny in spite of the prevailing platform character in preorogenic time. Important trends in the Alpine structural plan clearly were inherited from Precambrian structures. Precursory Alpine movements in Mesozoic time were strongest in Central Iran, although this region and the closely related Alborz (Elburz) Mountain area generally retained their epicontinental character, allowing for only a rudimentary geosynclinal development. More clearly geosynclinal conditions developed in peripheral fold belts: the Zagros, the Kopet Dagh, and the East Iranian ranges. Strong folding and thrusting during the Alpine orogeny proper in Late Cretaceous-Tertiary time affected most of Iran except the rigid Lut block in the eastern part of the country. The conventional tripartite division of Iran into an extensive median mass and two bordering ranges of geosynclinal origin (Zagros, Alborz) cannot be maintained. The writer replaces this oversimplified interpretation by recognizing the existence of more structural zones which differ in structural development and present tectonic style.",
    url = "https://doi.org/10.1306/5d25c4a5-16c1-11d7-8645000102c1865d",
    doi = "10.1306/5d25c4a5-16c1-11d7-8645000102c1865d",
    openalex = "W1993744042",
    references = "doi1023071794401"
}

Analysis of the sedimentary, volcanic, structural, and metamorphic chronology in mountain belts, and consideration of the implications of the new global tectonics (plate tectonics), strongly indicate that mountain belts are a consequence of plate evolution. It is proposed that mountain belts develop by the deformation and metamorphism of the sedimentary and volcanic assemblages of Atlantic-type continental margins. These assemblages result from the events associated with the rupture of continents and the expansion of oceans by lithosphere plate generation at oceanic ridges. The earliest assemblages thus developed are volcanic rocks and coarse clastic sediments deposited in fault-bounded troughs on a distending and segmenting continental crust, subsequently split apart and carried away from the ridge on essentially aseismic continental margins. As the continental margins move away from the ridge, nonvolcanic continental shelf and rise assemblages of orthoquartzite-carbonate, and lutite (shelf), and lutite, slump deposits, and turbidites (rise) accumulate. This kind of continental margin is transformed into an orogenic belt in one of two ways. If a trench develops near, or at, the continenal margin to consume lithosphere from the oceanic side, a mountain belt (cordilleran type) grows by dominantly thermal mechanisms related to the rise of calc-alkaline and basaltic magmas. Cordilleran-type mountain belts are characterized by paired metamorphic belts (blueschist on the oceanic side and high temperature on the continental side) and divergent thrusting and synorogenic sediment transport from the high-temperature volcanic axis. If the continental margin collides with an island arc, or with another continent, a collision-type mountain belt develops by dominantly mechanical processes. Where a continent/island arc collision occurs, the resulting mountains will be small (e.g., the Tertiary fold belt of northern New Guinea), and a new trench will develop on the oceanic side of the arc. Where a continent/continent collision occurs, the mountains will be large (e.g., the Himalayas), and the single trench zone of plate consumption is replaced by a wide zone of deformation. Collision-type mountain belts do not have paired metamorphic belts; they are characterized by a single dominant direction of thrusting and synorogenic sediment transport, away from the site of the trench over the underthrust plate. Stratigraphic sequences of mountain belts (geosynclinal sequences) match those asciated with present-day oceans, island arcs, and continental margins.

@article{doi101029jb075i014p02625,
    author = "Dewey, John and Bird, John",
    title = "Mountain belts and the new global tectonics",
    year = "1970",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "Analysis of the sedimentary, volcanic, structural, and metamorphic chronology in mountain belts, and consideration of the implications of the new global tectonics (plate tectonics), strongly indicate that mountain belts are a consequence of plate evolution. It is proposed that mountain belts develop by the deformation and metamorphism of the sedimentary and volcanic assemblages of Atlantic-type continental margins. These assemblages result from the events associated with the rupture of continents and the expansion of oceans by lithosphere plate generation at oceanic ridges. The earliest assemblages thus developed are volcanic rocks and coarse clastic sediments deposited in fault-bounded troughs on a distending and segmenting continental crust, subsequently split apart and carried away from the ridge on essentially aseismic continental margins. As the continental margins move away from the ridge, nonvolcanic continental shelf and rise assemblages of orthoquartzite-carbonate, and lutite (shelf), and lutite, slump deposits, and turbidites (rise) accumulate. This kind of continental margin is transformed into an orogenic belt in one of two ways. If a trench develops near, or at, the continenal margin to consume lithosphere from the oceanic side, a mountain belt (cordilleran type) grows by dominantly thermal mechanisms related to the rise of calc-alkaline and basaltic magmas. Cordilleran-type mountain belts are characterized by paired metamorphic belts (blueschist on the oceanic side and high temperature on the continental side) and divergent thrusting and synorogenic sediment transport from the high-temperature volcanic axis. If the continental margin collides with an island arc, or with another continent, a collision-type mountain belt develops by dominantly mechanical processes. Where a continent/island arc collision occurs, the resulting mountains will be small (e.g., the Tertiary fold belt of northern New Guinea), and a new trench will develop on the oceanic side of the arc. Where a continent/continent collision occurs, the mountains will be large (e.g., the Himalayas), and the single trench zone of plate consumption is replaced by a wide zone of deformation. Collision-type mountain belts do not have paired metamorphic belts; they are characterized by a single dominant direction of thrusting and synorogenic sediment transport, away from the site of the trench over the underthrust plate. Stratigraphic sequences of mountain belts (geosynclinal sequences) match those asciated with present-day oceans, island arcs, and continental margins.",
    url = "https://doi.org/10.1029/jb075i014p02625",
    doi = "10.1029/jb075i014p02625",
    openalex = "W2111555634",
    references = "doi101007bf02597153, doi101029jb073i006p01959, doi101029jb073i012p03661, doi101029jb073i018p05855, doi101038211676a0, doi1010382161276a0, doi101093petrology23277, doi101111j1365246x1969tb00259x, doi101130001676061969802409mcatuo20co2, doi1013065d25c4a516c111d78645000102c1865d, doi101785bssa0590010369"
}

Abstract Significant data on the structure, tectonics and stratigraphy of Ganga basin have been obtained from aeromagnetic, ground magnetic, gravity and seismic surveys and the deep drilling conducted in the basin during the last fifteen years, Based on these data, the Ganga basin has been defined as a major platform depression and classified into seven tectonic zones, viz., Monghyr-Saharsa ridge, East Uttar Pradesh shelf, Gandak depression, Faizabad ridge, West Uttar Pradesh shelf, Sarda depression and Delhi-Hardwar ridge. This classification is based on the continuation of major tectonic trends from the Peninsular shield into the Ganga basin, the variations in the total thickness of the sedimentary cover, and the basement configuration as deduced from different surveys. The sedimentary cover over most part of the Ganga basin is essentially composed of two main stratigraphic cum structural sequences representing the two main sedimentary stages in the geological evolution of the basin. The oldest, probably corresponding to the Vindhyans, is represented by stable to unstable shelf sediments composed of quartz-arenite-limestone-shale alternations. The younger sequence, unconformably overlying the Vindhyans, corresponds to the Neogene terrigenous clastics (Siwaliks). The structural and stratigraphic data of these sediments have been discussed. The presence of a profound unconformity between these two groups of sediments representing a considerable time gap ranging from (?) late Palaeozoic to Paleogene is an important factor in deciphering the tectonic evolution of the Himalaya. However, towards the northernmost depressed parts of the Ganga Basin, the age of the additional thickness of sediments intervening between the two above mentioned groups remains uncertain.

@article{doi1017491jgsi1971120302,
    author = "Sastri, V. V. and Bhandari, Laxminarayan and Raju, A. T. R. and Datta, Ashis",
    title = "Tectonic Framework and Subsurface Stratigraphy of the Ganga Basin",
    year = "1971",
    journal = "Journal of the Geological Society of India",
    abstract = "Abstract Significant data on the structure, tectonics and stratigraphy of Ganga basin have been obtained from aeromagnetic, ground magnetic, gravity and seismic surveys and the deep drilling conducted in the basin during the last fifteen years, Based on these data, the Ganga basin has been defined as a major platform depression and classified into seven tectonic zones, viz., Monghyr-Saharsa ridge, East Uttar Pradesh shelf, Gandak depression, Faizabad ridge, West Uttar Pradesh shelf, Sarda depression and Delhi-Hardwar ridge. This classification is based on the continuation of major tectonic trends from the Peninsular shield into the Ganga basin, the variations in the total thickness of the sedimentary cover, and the basement configuration as deduced from different surveys. The sedimentary cover over most part of the Ganga basin is essentially composed of two main stratigraphic cum structural sequences representing the two main sedimentary stages in the geological evolution of the basin. The oldest, probably corresponding to the Vindhyans, is represented by stable to unstable shelf sediments composed of quartz-arenite-limestone-shale alternations. The younger sequence, unconformably overlying the Vindhyans, corresponds to the Neogene terrigenous clastics (Siwaliks). The structural and stratigraphic data of these sediments have been discussed. The presence of a profound unconformity between these two groups of sediments representing a considerable time gap ranging from (?) late Palaeozoic to Paleogene is an important factor in deciphering the tectonic evolution of the Himalaya. However, towards the northernmost depressed parts of the Ganga Basin, the age of the additional thickness of sediments intervening between the two above mentioned groups remains uncertain.",
    url = "https://doi.org/10.17491/jgsi/1971/120302",
    doi = "10.17491/jgsi/1971/120302",
    openalex = "W2305792360"
}

The paper gives a review of the Palaeozoic successions of Kashmir and the region adjoining in the SE (Kishtwar, Pangi, Chamba). Special reference is given to the diverse notes on fossil contents of the beds. The b a s a l formations show a distinct geosynclinal (greywacke) facies. They range up from the Late Precambrian.to the Silurian as shown by rare fossil horizons. The T a n a w a l s (Ordovician-Upper Carboniferous) indicate a persistence of flyschoid deposition which has become more arenaceous. This facies is intertonguing with the shallow water facies of the M u t h Q u a r t z i t e (Devonian) and partly with the dark S y r i n g o t h y r i s L i m e s t o n e (L. Carb.) and the F e n e s t e l l a S h a l e s (Mid. Carb.). The stratigraphic range of the Tanawals becomes larger when followed from the inner to the outer (southwestern) zones of the mountains. Facies becomes more uniform with the deposition of the A g g 1 o m er a t i c S l a t e s (Up. Carb.). This formation has its unique character from climatic (glacial) influence and the beginning of volcanic activity. Thick lava flows follow — the P a n j a l T r a p s. In the Permian the G a n g a m o p t e r i s B e d s and marine Z e w a n S e r i e s are deposited on the trap. Locally, however, volcanicity persists into the Upper Triassic. GENERALIZED LOCATION

@article{openalexw2184690662,
    author = "Fuchs, Von G. and Gupta, Vikram",
    title = "Palaeozoic Stratigraphy of Kashmir, Kishtwar and Chamba (Panjab Himalayas)",
    year = "1971",
    abstract = "The paper gives a review of the Palaeozoic successions of Kashmir and the region adjoining in the SE (Kishtwar, Pangi, Chamba). Special reference is given to the diverse notes on fossil contents of the beds. The b a s a l formations show a distinct geosynclinal (greywacke) facies. They range up from the Late Precambrian.to the Silurian as shown by rare fossil horizons. The T a n a w a l s (Ordovician-Upper Carboniferous) indicate a persistence of flyschoid deposition which has become more arenaceous. This facies is intertonguing with the shallow water facies of the M u t h Q u a r t z i t e (Devonian) and partly with the dark S y r i n g o t h y r i s L i m e s t o n e (L. Carb.) and the F e n e s t e l l a S h a l e s (Mid. Carb.). The stratigraphic range of the Tanawals becomes larger when followed from the inner to the outer (southwestern) zones of the mountains. Facies becomes more uniform with the deposition of the A g g 1 o m er a t i c S l a t e s (Up. Carb.). This formation has its unique character from climatic (glacial) influence and the beginning of volcanic activity. Thick lava flows follow — the P a n j a l T r a p s. In the Permian the G a n g a m o p t e r i s B e d s and marine Z e w a n S e r i e s are deposited on the trap. Locally, however, volcanicity persists into the Upper Triassic. GENERALIZED LOCATION",
    openalex = "W2184690662"
}

Examination of more than 100 fault plane solutions for earthquakes within the Alpide belt between the Mid-Atlantic ridge and Eastern Iran shows that the deformation at present occurring is the result of small continental plates moving away from Eastern Turkey and Western Iran. This pattern of movement avoids thickening the continental crust over much of Turkey by consuming the Eastern Mediterranean sea floor instead. The rates of relative motion of two of the small plates involved, the Aegean and the Turkish plates, are estimated, but are only within perhaps 50 per cent of the true values. These estimates are then used to reconstruct the geometry of the Mediterranean 10 million years ago. The principal difference from the present geometry is the smooth curved coast which then formed the southern coast of Yugoslavia, Greece and Turkey. This coast has since been distorted by the motion of the two small plates. Similar complications have probably been common in older mountain belts, and therefore local geological features may not have been formed by the motion between major plates.

@article{doi101111j1365246x1972tb02351x,
    author = "McKenzie, Dan",
    title = "Active Tectonics of the Mediterranean Region",
    year = "1972",
    journal = "Geophysical Journal International",
    abstract = "Examination of more than 100 fault plane solutions for earthquakes within the Alpide belt between the Mid-Atlantic ridge and Eastern Iran shows that the deformation at present occurring is the result of small continental plates moving away from Eastern Turkey and Western Iran. This pattern of movement avoids thickening the continental crust over much of Turkey by consuming the Eastern Mediterranean sea floor instead. The rates of relative motion of two of the small plates involved, the Aegean and the Turkish plates, are estimated, but are only within perhaps 50 per cent of the true values. These estimates are then used to reconstruct the geometry of the Mediterranean 10 million years ago. The principal difference from the present geometry is the smooth curved coast which then formed the southern coast of Yugoslavia, Greece and Turkey. This coast has since been distorted by the motion of the two small plates. Similar complications have probably been common in older mountain belts, and therefore local geological features may not have been formed by the motion between major plates.",
    url = "https://doi.org/10.1111/j.1365-246x.1972.tb02351.x",
    doi = "10.1111/j.1365-246x.1972.tb02351.x",
    openalex = "W2155472085",
    references = "doi101029jb073i012p03661, doi101029jb073i018p05855, doi101029jz072i008p02131, doi101029rg009i001p00103, doi101038207343a0, doi1010382161276a0, doi101038224125a0, doi101038226239a0, doi101111j1365246x1969tb00259x, doi101111j1365246x1971tb02190x, doi10113000167606196071843peotca20co2, doi101144transed83387, doi101785bssa0590010369, sykes1967mechanism"
}

@article{powell1973plate,
    author = "Powell, C.McA. and Conaghan, P.J.",
    title = "Plate tectonics and the Himalayas",
    year = "1973",
    journal = "Earth and Planetary Science Letters",
    url = "https://doi.org/10.1016/0012-821x(73)90134-9",
    doi = "10.1016/0012-821x(73)90134-9",
    number = "1",
    openalex = "W2026301874",
    pages = "1-12",
    volume = "20",
    references = "doi101007bf01823808, doi101029jb073i006p02119, doi101029jb073i012p03661, doi101029jb075i014p02625, doi101038169679a0, doi101111j1365246x1971tb02190x, doi101785bssa0590010369, doi1023071794401, openalexw1515132582, openalexw1971150847, openalexw623436458"
}

Abstract The Tal Formation, containing datable fossil assemblages in the Lansdowne hills in Garhwal, occupies a crucial position at the top of the 6100-metre thick succession of predominantly unfossiliferous sediments constituting the Krol Nappe. The lithostratigraphic unit comprising of (i) Lower Permian fossil-bearing black shale (often phosphatic), mudstone, conglomeratic greywacke and mudstone, (ii) a variety of sandstone of varied colour and (iii) sandy, oolitic and shelly limestone, lithologically indistinguishable and tectonically inseparable from the formation recognized as the Tal, the limestone of the upper horizon of which has yielded Upper Permian fossils. The lower member of the Tal progressively thins out southward until finally disappearing so that the considerably attenuated middle member and the upper limestone member rest directly on the Krol, thus exhibiting transgressive overlap. The Permian Tal is unconformably capped by the Subathu of Eocene age, implying that the whole of Mesozoic group is missing in the Lesser Himalaya. The Krol which conformably underlies the Tal is not Permo-Triassic as commonly believed and the Blaini that rests upon the Nagthat cannot be equated with the Upper Carboniferous Talchir formation of Peninsular India. The occurrence of Lower Palaeozoic bryozoan remains in the slate and calcareous beds resting on the Nagthat quartzite in the Nandhaur valley, southeast of Nainital, corroborates the Lower Palaeozoic age assigned to the Blaini.

@article{doi1017491jgsi1975160201,
    author = "Valdiya, K. S.",
    title = "Lithology and Age of the Tal Formation in Garhwal, and Implication on Stratigraphic Scheme of Krol Belt in Kumaun Himalaya",
    year = "1975",
    journal = "Journal of the Geological Society of India",
    abstract = "Abstract The Tal Formation, containing datable fossil assemblages in the Lansdowne hills in Garhwal, occupies a crucial position at the top of the 6100-metre thick succession of predominantly unfossiliferous sediments constituting the Krol Nappe. The lithostratigraphic unit comprising of (i) Lower Permian fossil-bearing black shale (often phosphatic), mudstone, conglomeratic greywacke and mudstone, (ii) a variety of sandstone of varied colour and (iii) sandy, oolitic and shelly limestone, lithologically indistinguishable and tectonically inseparable from the formation recognized as the Tal, the limestone of the upper horizon of which has yielded Upper Permian fossils. The lower member of the Tal progressively thins out southward until finally disappearing so that the considerably attenuated middle member and the upper limestone member rest directly on the Krol, thus exhibiting transgressive overlap. The Permian Tal is unconformably capped by the Subathu of Eocene age, implying that the whole of Mesozoic group is missing in the Lesser Himalaya. The Krol which conformably underlies the Tal is not Permo-Triassic as commonly believed and the Blaini that rests upon the Nagthat cannot be equated with the Upper Carboniferous Talchir formation of Peninsular India. The occurrence of Lower Palaeozoic bryozoan remains in the slate and calcareous beds resting on the Nagthat quartzite in the Nandhaur valley, southeast of Nainital, corroborates the Lower Palaeozoic age assigned to the Blaini.",
    url = "https://doi.org/10.17491/jgsi/1975/160201",
    doi = "10.17491/jgsi/1975/160201",
    openalex = "W2521879744"
}

K/Ar dating of metamorphic aureoles of ultramafic intrusions (Oligocene-Miocene), crustal thinning and lithospheric extension, tectonic model; Spain, Morocco

@article{doi102475ajs27511,
    author = "Loomis, Timothy P.",
    title = "Tertiary mantle diapirism, orogeny, and plate tectonics east of the Strait of Gibraltar",
    year = "1975",
    journal = "American Journal of Science",
    abstract = "K/Ar dating of metamorphic aureoles of ultramafic intrusions (Oligocene-Miocene), crustal thinning and lithospheric extension, tectonic model; Spain, Morocco",
    url = "https://doi.org/10.2475/ajs.275.1.1",
    doi = "10.2475/ajs.275.1.1",
    openalex = "W2333266947"
}

Independent arguments based on topographic stress and crustal strength give upper limits of 200 bars and 300 bars, respectively, for the average shear stress on the intracontinental thrust fault that formed the Himalaya. According to either a one‐dimensional or a two‐dimensional fault model, such stresses could not have produced the Himalayan granites by friction, unless overthrusting velocity exceeded 30 cm/yr. More probably, Himalayan metamorphism was caused by exposure of continental crust to hot asthenosphere prior to the formation of the intracontinental thrust. Crust was exposed by peeling away of Indian subcrustal lithosphere in response to the force and moment exerted by the Tethyan slab. This detachment of buoyant crust from dense lithosphere better explains the metamorphic pattern and also explains why the distributed crustal shortening at the beginning of the collision orogeny was replaced by localized thrusting or intracontinental subduction.

@article{doi101029jb083ib10p04975,
    author = "Bird, Peter",
    title = "Initiation of intracontinental subduction in the Himalaya",
    year = "1978",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "Independent arguments based on topographic stress and crustal strength give upper limits of 200 bars and 300 bars, respectively, for the average shear stress on the intracontinental thrust fault that formed the Himalaya. According to either a one‐dimensional or a two‐dimensional fault model, such stresses could not have produced the Himalayan granites by friction, unless overthrusting velocity exceeded 30 cm/yr. More probably, Himalayan metamorphism was caused by exposure of continental crust to hot asthenosphere prior to the formation of the intracontinental thrust. Crust was exposed by peeling away of Indian subcrustal lithosphere in response to the force and moment exerted by the Tethyan slab. This detachment of buoyant crust from dense lithosphere better explains the metamorphic pattern and also explains why the distributed crustal shortening at the beginning of the collision orogeny was replaced by localized thrusting or intracontinental subduction.",
    url = "https://doi.org/10.1029/jb083ib10p04975",
    doi = "10.1029/jb083ib10p04975",
    openalex = "W1985152873",
    references = "doi1010160040195178901403, doi101029jb073i006p02119, doi101029jb076i005p01113, doi101029jz064i010p01521, doi101086627920, doi101111j1365246x1972tb06152x, doi101111j1365246x1975tb00631x, doi101126science1894201419, doi10113000167606197182563gotbdf20co2, doi102134agronj195400021962004600100016x, doi102475ajs27511, powell1973plate"
}

New fault plane solutions, Landsat photographs, and seismic refraction records show that rapid extension is now taking place in the northern and eastern parts of the Aegean sea region. The southern part of the Aegean has also been deformed by normal faulting but is now relatively inactive. In northwestern Greece and Albania there is a band of thrusting near the western coasts adjacent to a band of normal faulting further east. The pre-Miocene geology of the islands in the Aegean closely resembles that of Greece and Turkey, yet seismic refraction shows that the crust is now only about 30 km thick beneath the southern part of the sea, compared with nearly 50 km beneath Greece and western Turkey. These observations suggest that the Aegean has been stretched by a factor of two since the Miocene. This stretching can account for the high heat flow. The sinking slab produced by subduction along the Hellenic Arc may maintain the motions, though the geometry and widespread nature of the normal faulting is not easily explained. The motions in northwestern Greece and Albania cannot be driven in the same way because no slab exists in the area. They may be maintained by blobs of cold mantle detaching from the lower half of the lithosphere, produced by a thermal instability when the lithosphere is thickened by thrusting. Hence generation and destruction of the lower part of the lithosphere may occur beneath deforming continental crust without the production of any oceanic crust.

@article{doi101111j1365246x1978tb04759x,
    author = "McKenzie, Dan",
    title = "Active tectonics of the Alpine--Himalayan belt: the Aegean Sea and surrounding regions",
    year = "1978",
    journal = "Geophysical Journal International",
    abstract = "New fault plane solutions, Landsat photographs, and seismic refraction records show that rapid extension is now taking place in the northern and eastern parts of the Aegean sea region. The southern part of the Aegean has also been deformed by normal faulting but is now relatively inactive. In northwestern Greece and Albania there is a band of thrusting near the western coasts adjacent to a band of normal faulting further east. The pre-Miocene geology of the islands in the Aegean closely resembles that of Greece and Turkey, yet seismic refraction shows that the crust is now only about 30 km thick beneath the southern part of the sea, compared with nearly 50 km beneath Greece and western Turkey. These observations suggest that the Aegean has been stretched by a factor of two since the Miocene. This stretching can account for the high heat flow. The sinking slab produced by subduction along the Hellenic Arc may maintain the motions, though the geometry and widespread nature of the normal faulting is not easily explained. The motions in northwestern Greece and Albania cannot be driven in the same way because no slab exists in the area. They may be maintained by blobs of cold mantle detaching from the lower half of the lithosphere, produced by a thermal instability when the lithosphere is thickened by thrusting. Hence generation and destruction of the lower part of the lithosphere may occur beneath deforming continental crust without the production of any oceanic crust.",
    url = "https://doi.org/10.1111/j.1365-246x.1978.tb04759.x",
    doi = "10.1111/j.1365-246x.1978.tb04759.x",
    openalex = "W2048403692",
    references = "doi101038226239a0, doi101111j1365246x1969tb00259x"
}

We present a study of the active tectonics of central Asia based on an interpretation of Landsat imagery and supplemented with published field observations and seismic data. Reverse faulting dominates the tectonics of the Tien Shan but is associated with prominent northwest trending right lateral strike slip fault systems. Both types of faulting imply approximately north‐south maximum compressive stress. The active tectonics of the Altai and of southern Mongolia are controlled by largescale conjugate strike slip faulting; left lateral on east‐west planes and right lateral on north‐northwest planes. This implies that the maximum compressive stress is oriented approximately northeast‐southwest. Farther north, strike slip faulting gives way to predominantly normal faulting in the Baykal rift system. We interpret all of the active faulting to be a consequence of lateral displacements of the crust caused by the penetration of the Indian subcontinent of Eurasia. We also interpret the gradual change from thrust faulting and high altitudes in the south and west to normal faulting and lower mean elevations in the north and east to reflect a smooth change in the average state of stress. This suggests that the details of the complex intracontinental deformation in Asia are better described by the deformation of a continuum than by the relative motion of a small number of rigid blocks. Intracontinental rifting in the northeast, in particular, may result from a state of stress analogous to the secondary tension that commonly arises within bounded plastic materials indented by a rigid die.

@article{doi101029jb084ib07p03425,
    author = "Tapponnier, Paul and Molnár, Péter",
    title = "Active faulting and cenozoic tectonics of the Tien Shan, Mongolia, and Baykal Regions",
    year = "1979",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "We present a study of the active tectonics of central Asia based on an interpretation of Landsat imagery and supplemented with published field observations and seismic data. Reverse faulting dominates the tectonics of the Tien Shan but is associated with prominent northwest trending right lateral strike slip fault systems. Both types of faulting imply approximately north‐south maximum compressive stress. The active tectonics of the Altai and of southern Mongolia are controlled by largescale conjugate strike slip faulting; left lateral on east‐west planes and right lateral on north‐northwest planes. This implies that the maximum compressive stress is oriented approximately northeast‐southwest. Farther north, strike slip faulting gives way to predominantly normal faulting in the Baykal rift system. We interpret all of the active faulting to be a consequence of lateral displacements of the crust caused by the penetration of the Indian subcontinent of Eurasia. We also interpret the gradual change from thrust faulting and high altitudes in the south and west to normal faulting and lower mean elevations in the north and east to reflect a smooth change in the average state of stress. This suggests that the details of the complex intracontinental deformation in Asia are better described by the deformation of a continuum than by the relative motion of a small number of rigid blocks. Intracontinental rifting in the northeast, in particular, may result from a state of stress analogous to the secondary tension that commonly arises within bounded plastic materials indented by a rigid die.",
    url = "https://doi.org/10.1029/jb084ib07p03425",
    doi = "10.1029/jb084ib07p03425",
    openalex = "W1964599463"
}

Abstract Detrital framework modes of sandstone suites from different kinds of basins are a function of provenance types governed by plate tectonics. Quartzose sands from continental cratons are widespread within interior basins, platform successions, miogeoclinal wedges, and opening ocean basins. Arkosic sands from uplifted basement blocks are present locally in rift troughs and in wrench basins related to transform ruptures. Volcaniclastic lithic sands and more complex volcano-plutonic sands derived from magmatic arcs are present in trenches, forearc basins, and marginal seas. Recycled orogenic sands, rich in quartz or chert plus other lithic fragments and derived from subduction complexes, collision orogens, and foreland uplifts, are present in closing ocean basins, diverse successor basins, and foreland basins. Triangular diagrams showing framework proportions of quartz, the two feldspars, polycrystalline quartzose lithics, and unstable lithics of volcanic and sedimentary parentage successfully distinguish the key provenance types. Relations between provenance and basin are Important for hydrocarbon exploration because sand frameworks of contrasting detrital compositions respond differently to diagenesis, and thus display different trends of porosity reduction with depth of burial.

@article{doi1013062f9188fb16ce11d78645000102c1865d,
    author = "Dickinson, William R. and Suczek, Christopher A.",
    title = "Plate Tectonics and Sandstone Compositions",
    year = "1979",
    journal = "AAPG Bulletin",
    abstract = "Abstract Detrital framework modes of sandstone suites from different kinds of basins are a function of provenance types governed by plate tectonics. Quartzose sands from continental cratons are widespread within interior basins, platform successions, miogeoclinal wedges, and opening ocean basins. Arkosic sands from uplifted basement blocks are present locally in rift troughs and in wrench basins related to transform ruptures. Volcaniclastic lithic sands and more complex volcano-plutonic sands derived from magmatic arcs are present in trenches, forearc basins, and marginal seas. Recycled orogenic sands, rich in quartz or chert plus other lithic fragments and derived from subduction complexes, collision orogens, and foreland uplifts, are present in closing ocean basins, diverse successor basins, and foreland basins. Triangular diagrams showing framework proportions of quartz, the two feldspars, polycrystalline quartzose lithics, and unstable lithics of volcanic and sedimentary parentage successfully distinguish the key provenance types. Relations between provenance and basin are Important for hydrocarbon exploration because sand frameworks of contrasting detrital compositions respond differently to diagenesis, and thus display different trends of porosity reduction with depth of burial.",
    url = "https://doi.org/10.1306/2f9188fb-16ce-11d7-8645000102c1865d",
    doi = "10.1306/2f9188fb-16ce-11d7-8645000102c1865d",
    openalex = "W2023601146",
    references = "doi10113000167606197586273hmffdi20co2, doi10130674d720182b2111d78648000102c1865d, openalexw2094255421"
}

The Manaslu pluton is one of 10 leucogranites that formed in the overthrusted Higher Himalaya after the Indo‐Eurasian collision. Field and analytical data indicate that the underlying migmatites of the Tibetan Slab may be where the leucogranitic melts were generated. The Himalayan crustal thrusting of a hot slab over a rather cold volcano‐sedimentary pile [Le Fort, 1975a] provides the necessary release of fluids. These fluids cross the Main Central Thrust (MCT), induce the partial anatexis of the overheated Tibetan Slab, and produce a leucogranitic magma. The emplacement of the magma at first is located along the main disharmonic plane above the MCT, between the infrastructure and the superstructure. There it generates a convective hydrothermal system extending very far laterally according to the stratification of permeabilities. Progressive emplacement of the granite proceeds as the convected fluids, including the fluids released by the saturated magma, dissolve the mainly calcareous host rocks of Tibetan sedimentaries. A frozen image of this ‘caving out’ progression is given by the extensive network of granitic dikes outside the pluton. The two quite independant fluid cycles of the generation and of the emplacement were triggered or guided by the tectonics due to collision. This two‐fold model, dominated by fluid activity, may be of importance for other leucogranites and granites.

@article{doi101029jb086ib11p10545,
    author = "Fort, Patrick Le",
    title = "Manaslu leucogranite: A collision signature of the Himalaya: A model for its genesis and emplacement",
    year = "1981",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "The Manaslu pluton is one of 10 leucogranites that formed in the overthrusted Higher Himalaya after the Indo‐Eurasian collision. Field and analytical data indicate that the underlying migmatites of the Tibetan Slab may be where the leucogranitic melts were generated. The Himalayan crustal thrusting of a hot slab over a rather cold volcano‐sedimentary pile [Le Fort, 1975a] provides the necessary release of fluids. These fluids cross the Main Central Thrust (MCT), induce the partial anatexis of the overheated Tibetan Slab, and produce a leucogranitic magma. The emplacement of the magma at first is located along the main disharmonic plane above the MCT, between the infrastructure and the superstructure. There it generates a convective hydrothermal system extending very far laterally according to the stratification of permeabilities. Progressive emplacement of the granite proceeds as the convected fluids, including the fluids released by the saturated magma, dissolve the mainly calcareous host rocks of Tibetan sedimentaries. A frozen image of this ‘caving out’ progression is given by the extensive network of granitic dikes outside the pluton. The two quite independant fluid cycles of the generation and of the emplacement were triggered or guided by the tectonics due to collision. This two‐fold model, dominated by fluid activity, may be of importance for other leucogranites and granites.",
    url = "https://doi.org/10.1029/jb086ib11p10545",
    doi = "10.1029/jb086ib11p10545",
    openalex = "W2151869859"
}

In the Karakorum Range there is a structurally complicated Cretaceous are comprising the Kohistan sequence. On its northern side the Northern Suture consists of a mega-mélange and is bounded to the S by tightly folded pillow-bearing volcanics and sediments. To the S the Kohistan Plutonic Belt consists of (southwards): (a) early foliated and late post-tectonic tonalites and diorites, (b) aplites and pegmatites (up to 30% of rock volume), (c) basic dykes up to 10 m thick, (d) the Chilas Complex, a stratiform cumulate body over 300 km long and 8 km thick (chromite-layered dunites, gabbros and norites) with a low pressure granulite-facies mineral fabric of tectonic origin, (e) an amphibolite belt with a complex mixture of other rocks, and (f) the Jijal Complex, a 200 km 2 tectonic wedge of high pressure granulites and chromite-layered dunites. Cumulate graded units in the Chilas Complex show that it is folded by an isoclinal anticline (F 1). The mid-upper crust of the are is folded by a 50 km half-wavelength F 2, syncline. The whole Kohistan sequence with its two phases of isoclinal folds was tilted during Himalayan collision so that the structures are now subvertical. The Southern Suture (Main Mantle Thrust) has a wedge of glaucophane schists. The Indian plate contains a basement of psammites and schists intruded by Cambrian granites and overlain by isoclinally folded and metamorphosed carbonates and shales.

@article{doi101144gsjgs13930299,
    author = "Coward, M. P. and Jan, M. Q. and Rex, D. C. and Tarney, J. and Thirlwall, M. F. and Windley, Brian F.",
    title = "Geo-tectonic framework of the Himalaya of N Pakistan",
    year = "1982",
    journal = "Journal of the Geological Society",
    abstract = "In the Karakorum Range there is a structurally complicated Cretaceous are comprising the Kohistan sequence. On its northern side the Northern Suture consists of a mega-mélange and is bounded to the S by tightly folded pillow-bearing volcanics and sediments. To the S the Kohistan Plutonic Belt consists of (southwards): (a) early foliated and late post-tectonic tonalites and diorites, (b) aplites and pegmatites (up to 30\% of rock volume), (c) basic dykes up to 10 m thick, (d) the Chilas Complex, a stratiform cumulate body over 300 km long and 8 km thick (chromite-layered dunites, gabbros and norites) with a low pressure granulite-facies mineral fabric of tectonic origin, (e) an amphibolite belt with a complex mixture of other rocks, and (f) the Jijal Complex, a 200 km 2 tectonic wedge of high pressure granulites and chromite-layered dunites. Cumulate graded units in the Chilas Complex show that it is folded by an isoclinal anticline (F 1). The mid-upper crust of the are is folded by a 50 km half-wavelength F 2, syncline. The whole Kohistan sequence with its two phases of isoclinal folds was tilted during Himalayan collision so that the structures are now subvertical. The Southern Suture (Main Mantle Thrust) has a wedge of glaucophane schists. The Indian plate contains a basement of psammites and schists intruded by Cambrian granites and overlain by isoclinally folded and metamorphosed carbonates and shales.",
    url = "https://doi.org/10.1144/gsjgs.139.3.0299",
    doi = "10.1144/gsjgs.139.3.0299",
    openalex = "W2004912236"
}

@article{doi1010160040195184901148,
    author = "Thakur, V. C. and Misra, D.K.",
    title = "Tectonic framework of the Indus and Shyok suture zones in Eastern Ladakh, Northwest Himalaya",
    year = "1984",
    journal = "Tectonophysics",
    url = "https://doi.org/10.1016/0040-1951(84)90114-8",
    doi = "10.1016/0040-1951(84)90114-8",
    openalex = "W2022444111"
}

Fault plane solutions and well‐determined focal depths of medium‐sized earthquakes, topography, and Landsat imagery in conjunction with seismicity maps, cross sections, and available geological information are used to investigate the present tectonics of the Himalayan continental collision zone. Most of the accurately located epicenters of events along the Himalayan arc (78°E–95°E) that occurred between 1961 and 1981 are concentrated in a narrow zone, about 50 km wide, lying between the northerly dipping Main Boundary (MBT) and Main Central (MCT) thrusts. Most of these events are located just south of the MCT. Though the epicenters of the events are, in general, well located, their depths as determined by teleseismic travel time data are very unreliable. Events with accurately determined depths obtained from identification of surface‐reflected phases define a simple, planar zone from about 10‐km and 20‐km depth, with an apparent dip of about 15°. This result is all the more remarkable considering that the events used were located along about an 1800‐km length of the Himalyan arc. Except for one, all available focal mechanisms of events within this zone indicate shallow (≲30°), north dipping thrusts. This shallow, north dipping zone apparently defines a part of the detachment that separates the underthrusting Indian plate from the Lesser Himalayan crustal block. The spatial extent and the geometry of this interplate thrust zone strongly indicate that the MBT and nearby subsidiary surface and blind thrusts, rather than the MCT, are currently the most active structures of the Himalayan arc. We suggest that the great Himalayan earthquakes (M >8) occur along the same detachment surface as defined by the thrust‐type, medium‐sized events. Events located to the south of the MBT and beneath the Ganges foredeep show normal faulting with T axes perpendicular to the Himalayan trend. The above results suggest that the Indian continental plate is underthrusting the Himalayan crustal blocks in a relatively coherent and simple geometry and that this geometry is not much different from that observed along oceanic subduction zones. The November 19, 1980, earthquake that occurred near the MCT (near 88.5°E) shows a predominantly strike‐slip focal mechanism. One of the nodal planes of this mechanism is transverse to the Himalayan structural grain, and moreover, this plane has a trend similar to that of the recently mapped Yadong‐Gulu rift in the Tethyan Himalaya and in southern Tibet just northeast of the earthquake. We interpret this predominantly left‐lateral, strike‐slip mechanism to indicate a possible genetic relationship between transverse structural features in the Underthrusting Indian plate (the Kishangang basement fault) and the upper Himalayan blocks and Tibet.

@article{doi101029jb089ib02p01147,
    author = "Ni, James and Barazangi, Muawia",
    title = "Seismotectonics of the Himalayan Collision Zone: Geometry of the underthrusting Indian Plate beneath the Himalaya",
    year = "1984",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "Fault plane solutions and well‐determined focal depths of medium‐sized earthquakes, topography, and Landsat imagery in conjunction with seismicity maps, cross sections, and available geological information are used to investigate the present tectonics of the Himalayan continental collision zone. Most of the accurately located epicenters of events along the Himalayan arc (78°E–95°E) that occurred between 1961 and 1981 are concentrated in a narrow zone, about 50 km wide, lying between the northerly dipping Main Boundary (MBT) and Main Central (MCT) thrusts. Most of these events are located just south of the MCT. Though the epicenters of the events are, in general, well located, their depths as determined by teleseismic travel time data are very unreliable. Events with accurately determined depths obtained from identification of surface‐reflected phases define a simple, planar zone from about 10‐km and 20‐km depth, with an apparent dip of about 15°. This result is all the more remarkable considering that the events used were located along about an 1800‐km length of the Himalyan arc. Except for one, all available focal mechanisms of events within this zone indicate shallow (≲30°), north dipping thrusts. This shallow, north dipping zone apparently defines a part of the detachment that separates the underthrusting Indian plate from the Lesser Himalayan crustal block. The spatial extent and the geometry of this interplate thrust zone strongly indicate that the MBT and nearby subsidiary surface and blind thrusts, rather than the MCT, are currently the most active structures of the Himalayan arc. We suggest that the great Himalayan earthquakes (M >8) occur along the same detachment surface as defined by the thrust‐type, medium‐sized events. Events located to the south of the MBT and beneath the Ganges foredeep show normal faulting with T axes perpendicular to the Himalayan trend. The above results suggest that the Indian continental plate is underthrusting the Himalayan crustal blocks in a relatively coherent and simple geometry and that this geometry is not much different from that observed along oceanic subduction zones. The November 19, 1980, earthquake that occurred near the MCT (near 88.5°E) shows a predominantly strike‐slip focal mechanism. One of the nodal planes of this mechanism is transverse to the Himalayan structural grain, and moreover, this plane has a trend similar to that of the recently mapped Yadong‐Gulu rift in the Tethyan Himalaya and in southern Tibet just northeast of the earthquake. We interpret this predominantly left‐lateral, strike‐slip mechanism to indicate a possible genetic relationship between transverse structural features in the Underthrusting Indian plate (the Kishangang basement fault) and the upper Himalayan blocks and Tibet.",
    url = "https://doi.org/10.1029/jb089ib02p01147",
    doi = "10.1029/jb089ib02p01147",
    openalex = "W1983049944",
    references = "doi101016004019517690069x, doi101029gd003p0215"
}

About 3.4 Ga ago voluminous calc-alkaline magmas represented by the granitoid gneisses of southern India were emplaced into a now poorly preserved non-continental crust. Unstable ensialic basins, initiated at about 3.0 Ga, were filled with volcanic and sedimentary rocks up to about 2.6 Ga. This basement-cover sequence was deformed at the close of the Archaean, first by northward accretion and thickening of several crustal slabs formerly separated by prisms of stable shelf sediments. Structures produced by this episode were refolded and dislocated by large N-S strike-slip shear belts, to impart intense, steep planar fabrics to large volumes of the crust. Fluids rich in CO₂, possibly derived from sedimentary material driven beneath the crustal slabs by the thickening mechanism, purged the deep crust of H₂O to form granulites. Upward migration of hot H₂O-rich fluids encouraged partial melting at intermediate crustal levels. These late-Archaean tectonic and thermal events began soon after the close of basin filling and extended possibly to 2.5 Ga. The close spatial and temporal relationships between immense dyke swarms and 1.7 to 1.2 Ga sedimentary basins are believed to reflect protracted thermal disturbance beneath the Archaean craton in the mid- to late-Proterozoic. Late-Proterozoic tectonism resulted in westward overthrusting and thermal reworking of Archaean crust and transcurrent shear belts which juxtaposed dissimilar Archaean blocks.

@article{doi101086628831,
    author = "Drury, S. A. and Harris, Nigel and Holt, R. W. and Reeves-Smith, G. J. and Wightman, R. T.",
    title = "Precambrian Tectonics and Crustal Evolution in South India",
    year = "1984",
    journal = "The Journal of Geology",
    abstract = "About 3.4 Ga ago voluminous calc-alkaline magmas represented by the granitoid gneisses of southern India were emplaced into a now poorly preserved non-continental crust. Unstable ensialic basins, initiated at about 3.0 Ga, were filled with volcanic and sedimentary rocks up to about 2.6 Ga. This basement-cover sequence was deformed at the close of the Archaean, first by northward accretion and thickening of several crustal slabs formerly separated by prisms of stable shelf sediments. Structures produced by this episode were refolded and dislocated by large N-S strike-slip shear belts, to impart intense, steep planar fabrics to large volumes of the crust. Fluids rich in CO₂, possibly derived from sedimentary material driven beneath the crustal slabs by the thickening mechanism, purged the deep crust of H₂O to form granulites. Upward migration of hot H₂O-rich fluids encouraged partial melting at intermediate crustal levels. These late-Archaean tectonic and thermal events began soon after the close of basin filling and extended possibly to 2.5 Ga. The close spatial and temporal relationships between immense dyke swarms and 1.7 to 1.2 Ga sedimentary basins are believed to reflect protracted thermal disturbance beneath the Archaean craton in the mid- to late-Proterozoic. Late-Proterozoic tectonism resulted in westward overthrusting and thermal reworking of Archaean crust and transcurrent shear belts which juxtaposed dissimilar Archaean blocks.",
    url = "https://doi.org/10.1086/628831",
    doi = "10.1086/628831",
    openalex = "W1971892298",
    references = "doi1010160191814180900413"
}

Granites may be subdivided according to their intrusive settings into four main groups—ocean ridge granites (ORG), volcanic arc granites (VAG), within plate granites (WPG) and collision granites (COLG)—and the granites within each group may be further subdivided according to their precise settings and petrological characteristics. Using a data bank containing over 600 high quality trace element analyses of granites from known settings, it can be demonstrated using ORG-normalized geochemical patterns and element-SiO2 plots that most of these granite groups exhibit distinctive trace element characteristics. Discrimination of ORG, VAG, WPG and syn-COLG is most effective in Rb−Y−Nb and Rb−Yb−Ta space, particularly on projections of Y−Nb, Yb−Ta, Rb−(Y + Nb) and Rb−(Yb + Ta). Discrimination boundaries, though drawn empirically, can be shown by geochemical modelling to have a theoretical basis in the different petrogenetic histories of the various granite groups. Post-collision granites present the main problem of tectonic classification, since their characteristics depend on the thickness and composition of the lithosphere involved in the collision event and on the precise timing and location of magmatism. Provided they are coupled with a consideration of geological constraints, however, studies of trace element compositions in granites can clearly help in the elucidation of post-Archaean tectonic settings.

@article{doi101093petrology254956,
    author = "Pearce, Julian A. and Harris, Nigel and Tindle, A. G.",
    title = "Trace Element Discrimination Diagrams for the Tectonic Interpretation of Granitic Rocks",
    year = "1984",
    journal = "Journal of Petrology",
    abstract = "Granites may be subdivided according to their intrusive settings into four main groups—ocean ridge granites (ORG), volcanic arc granites (VAG), within plate granites (WPG) and collision granites (COLG)—and the granites within each group may be further subdivided according to their precise settings and petrological characteristics. Using a data bank containing over 600 high quality trace element analyses of granites from known settings, it can be demonstrated using ORG-normalized geochemical patterns and element-SiO2 plots that most of these granite groups exhibit distinctive trace element characteristics. Discrimination of ORG, VAG, WPG and syn-COLG is most effective in Rb−Y−Nb and Rb−Yb−Ta space, particularly on projections of Y−Nb, Yb−Ta, Rb−(Y + Nb) and Rb−(Yb + Ta). Discrimination boundaries, though drawn empirically, can be shown by geochemical modelling to have a theoretical basis in the different petrogenetic histories of the various granite groups. Post-collision granites present the main problem of tectonic classification, since their characteristics depend on the thickness and composition of the lithosphere involved in the collision event and on the precise timing and location of magmatism. Provided they are coupled with a consideration of geological constraints, however, studies of trace element compositions in granites can clearly help in the elucidation of post-Archaean tectonic settings.",
    url = "https://doi.org/10.1093/petrology/25.4.956",
    doi = "10.1093/petrology/25.4.956",
    openalex = "W2108971421",
    references = "doi101007bf00374895, doi101007bf00375192, doi101007bf00384745, doi1010160009254177900572, doi1010160012821x70900580, doi1010160012821x82900073, doi1010160012821x82901200, doi1010160012825276900520, doi1010160016703774901495, doi101093petrology254894, doi101093petrology254956, openalexw2554295816"
}

Over 80 new fault plane solutions, combined with satellite imagery as well as both modern and historical observations of earthquake faulting, are used to investigate the active tectonics of the Middle East between western Turkey and Pakistan. The deformation of the western part of this region is dominated by the movement of continental material laterally away from the Lake Van region in eastern Turkey. This movement helps to avoid crustal thickening in the Van region, and allows some of the shortening between Arabia and Eurasia to be taken up by the thrusting of continental material over oceanic-type basement in the southern Caspian, Mediterranean, Makran and Black Sea. Thus central Turkey, bounded by the North and East Anatolian strike-slip faults, is moving west from the Van region and overrides the eastern Mediterranean at two intermediate depth seismic zones: one extending between Antalya Bay and southern Cyprus, and the other further west in the Hellenic Trench. The motion of northern Iran eastwards from the Van region is achieved mainly by a conjugate system of strike-slip faults and leads to the low angle thrusting of Iran over the southern Caspian Sea. The seismicity of the Caucasus shows predominantly shortening perpendicular to the regional strike, but there is also some minor elongation along the strike of the belt as the Causcasus overrides the Caspian and Black Seas. The deformation of the eastern part of this region is dominated by the shortening of Iran against the stable borders of Turkmenistan and Afghanistan. The north-east direction of compression seen in Zagros is also seen in north-east Iran and the Kopet Dag, where the shortening is taken up by a combination of strike-slip and thrust faulting. Large structural as well as palaeomagnetic rotations are likely to have occurred in NE Iran as a result of this style of deformation. North-south strike-slip faults in southern Iran allow some movement of material away from the collision zone in NE Iran towards the Makran subduction zone, where genuinely intermediate depth seismicity is seen. Within this broad deforming belt large areas, such as central Turkey, NW Iran (Azerbaijan), central Iran and the southern Caspian, appear to be almost aseismic and therefore to behave as relatively rigid blocks surrounded by active belts 200-300 km wide. The motion of these blocks can usefully be described by poles of rotation. The poles presented in this paper predict motions consistent with those observed and also predict the opening of the Gulf of Iskenderun NE of Cyprus, the change within the Zagros mountains from strike-slip faulting in the NW to intense thrusting in the SE, and the relatively feeble seismicity in SE Iran (Baluchistan). This description also explains why the north-south structures along the Iran-Afghanistan border do not cut the east-west ranges of the Makran. Within the active belts surrounding the relatively aseismic blocks a continuum approach is needed for a description of the deformation, even though motions at the surface may be concentrated on faults. The evolution of fault systems within the active zones is controlled by geometric constraints, such as the requirement that simultaneously active faults do not, in general, intersect. Many of the active processes discussed in this paper, particularly large-scale rotations and lateral movement along the regional strike, are likely to have caused substantial complexities in older mountain belts and should be accounted for in any reconstructions of them.

@article{doi101111j1365246x1984tb01931x,
    author = "Jackson, James and McKenzie, Dan",
    title = "Active tectonics of the Alpine--Himalayan Belt between western Turkey and Pakistan",
    year = "1984",
    journal = "Geophysical Journal International",
    abstract = "Over 80 new fault plane solutions, combined with satellite imagery as well as both modern and historical observations of earthquake faulting, are used to investigate the active tectonics of the Middle East between western Turkey and Pakistan. The deformation of the western part of this region is dominated by the movement of continental material laterally away from the Lake Van region in eastern Turkey. This movement helps to avoid crustal thickening in the Van region, and allows some of the shortening between Arabia and Eurasia to be taken up by the thrusting of continental material over oceanic-type basement in the southern Caspian, Mediterranean, Makran and Black Sea. Thus central Turkey, bounded by the North and East Anatolian strike-slip faults, is moving west from the Van region and overrides the eastern Mediterranean at two intermediate depth seismic zones: one extending between Antalya Bay and southern Cyprus, and the other further west in the Hellenic Trench. The motion of northern Iran eastwards from the Van region is achieved mainly by a conjugate system of strike-slip faults and leads to the low angle thrusting of Iran over the southern Caspian Sea. The seismicity of the Caucasus shows predominantly shortening perpendicular to the regional strike, but there is also some minor elongation along the strike of the belt as the Causcasus overrides the Caspian and Black Seas. The deformation of the eastern part of this region is dominated by the shortening of Iran against the stable borders of Turkmenistan and Afghanistan. The north-east direction of compression seen in Zagros is also seen in north-east Iran and the Kopet Dag, where the shortening is taken up by a combination of strike-slip and thrust faulting. Large structural as well as palaeomagnetic rotations are likely to have occurred in NE Iran as a result of this style of deformation. North-south strike-slip faults in southern Iran allow some movement of material away from the collision zone in NE Iran towards the Makran subduction zone, where genuinely intermediate depth seismicity is seen. Within this broad deforming belt large areas, such as central Turkey, NW Iran (Azerbaijan), central Iran and the southern Caspian, appear to be almost aseismic and therefore to behave as relatively rigid blocks surrounded by active belts 200-300 km wide. The motion of these blocks can usefully be described by poles of rotation. The poles presented in this paper predict motions consistent with those observed and also predict the opening of the Gulf of Iskenderun NE of Cyprus, the change within the Zagros mountains from strike-slip faulting in the NW to intense thrusting in the SE, and the relatively feeble seismicity in SE Iran (Baluchistan). This description also explains why the north-south structures along the Iran-Afghanistan border do not cut the east-west ranges of the Makran. Within the active belts surrounding the relatively aseismic blocks a continuum approach is needed for a description of the deformation, even though motions at the surface may be concentrated on faults. The evolution of fault systems within the active zones is controlled by geometric constraints, such as the requirement that simultaneously active faults do not, in general, intersect. Many of the active processes discussed in this paper, particularly large-scale rotations and lateral movement along the regional strike, are likely to have caused substantial complexities in older mountain belts and should be accounted for in any reconstructions of them.",
    url = "https://doi.org/10.1111/j.1365-246x.1984.tb01931.x",
    doi = "10.1111/j.1365-246x.1984.tb01931.x",
    openalex = "W2133274607",
    references = "doi1010160012821x78900511, doi1010160012821x78900717, doi1010160040195178901403, doi101029jb088ib05p04183, doi101029rg016i004p00621, doi101139e81019, doi101144gsjgs13950605, doi1013062f918a8b16ce11d78645000102c1865d, openalexw1491817880"
}

@article{doi1010160012821x85901657,
    author = "Petterson, Michael G. and Windley, Brian F.",
    title = "RbSr dating of the Kohistan arc-batholith in the Trans-Himalaya of north Pakistan, and tectonic implications",
    year = "1985",
    journal = "Earth and Planetary Science Letters",
    url = "https://doi.org/10.1016/0012-821x(85)90165-7",
    doi = "10.1016/0012-821x(85)90165-7",
    openalex = "W2024259689",
    references = "coward1986collision, doi1010160012821x82900073, doi1010160024493785900192, doi1010160040195184901148, doi101029jb086ib11p10545, doi101038311615a0, doi101038311621a0, doi101144gsjgs13930299, openalexw2554295816, openalexw574151162"
}

Summary West Himalayan tectonics involve the collision of microplates between the Indian and Asian Plates. The Kohistan Complex consists largely of tightly folded basic volcanics and sediments generated as Late Jurassic to Late Cretaceous island arcs. These were intruded by post-folding Mid-Cretaceous — Eocene plutonics produced from continued subduction of the Indian Plate after closure of a suture between Kohistan and the Karakorum. The Himalayan structures show major thrust sheets and the Kohistan Arc is essentially a crustal ‘pop-up’ with southward-upright and northward-verging structures developed above a thick ductile decoupling zone (the Indus Suture), which can be traced for >100 km beneath Kohistan on large reentrants. This pop-up formed by a two stage process, closure of the Northern Suture followed by closure of the southern Indus Suture. Granitic rocks of the Kohistan-Ladakh Batholith (dated at ≅ 100-40 Ma) post-date most of the structures related to the Northern Suture but were deformed and carried southwards on shear structures related to the Indus Suture. Post-collisional deformation carried this Kohistan Complex on deep decoupling zones over the Indian Plate on a series of imbricated gneiss sheets, the thrusts climbing up section in the movement direction so that in the far S some override their own molasse debris. Folds above these deep decoupling zones deformed their overlying thrust sheets into large antiforms—i.e. the Nanga Parbat and Hazara Syntaxes. The Nanga Parbat Syntaxis probably formed due to a shear couple near a branch line where one of the main Himalayan thrusts joined the Indus Suture beneath Kohistan. Crustal delamination, to produce the imbricated gneiss sheets, could not account for all the displacement of India into Asia, suggested by palaeomagnetic data. There must also have been lateral displacement as demonstrated by the large oblique-slip shear zone in the Hunza Valley, N of Kohistan.

@article{coward1986collision,
    author = "Coward, Michael P. and Rex, David C. and Asif Khan, M. and Windley, Brian F. and Broughton, Roger D. and Luff, Ian W. and Petterson, Michael G. and Pudsey, Carol J.",
    title = "Collision tectonics in the NW Himalayas",
    year = "1986",
    journal = "Geological Society, London, Special Publications",
    abstract = "Summary West Himalayan tectonics involve the collision of microplates between the Indian and Asian Plates. The Kohistan Complex consists largely of tightly folded basic volcanics and sediments generated as Late Jurassic to Late Cretaceous island arcs. These were intruded by post-folding Mid-Cretaceous — Eocene plutonics produced from continued subduction of the Indian Plate after closure of a suture between Kohistan and the Karakorum. The Himalayan structures show major thrust sheets and the Kohistan Arc is essentially a crustal ‘pop-up’ with southward-upright and northward-verging structures developed above a thick ductile decoupling zone (the Indus Suture), which can be traced for >100 km beneath Kohistan on large reentrants. This pop-up formed by a two stage process, closure of the Northern Suture followed by closure of the southern Indus Suture. Granitic rocks of the Kohistan-Ladakh Batholith (dated at ≅ 100-40 Ma) post-date most of the structures related to the Northern Suture but were deformed and carried southwards on shear structures related to the Indus Suture. Post-collisional deformation carried this Kohistan Complex on deep decoupling zones over the Indian Plate on a series of imbricated gneiss sheets, the thrusts climbing up section in the movement direction so that in the far S some override their own molasse debris. Folds above these deep decoupling zones deformed their overlying thrust sheets into large antiforms—i.e. the Nanga Parbat and Hazara Syntaxes. The Nanga Parbat Syntaxis probably formed due to a shear couple near a branch line where one of the main Himalayan thrusts joined the Indus Suture beneath Kohistan. Crustal delamination, to produce the imbricated gneiss sheets, could not account for all the displacement of India into Asia, suggested by palaeomagnetic data. There must also have been lateral displacement as demonstrated by the large oblique-slip shear zone in the Hunza Valley, N of Kohistan.",
    url = "https://doi.org/10.1144/gsl.sp.1986.019.01.11",
    doi = "10.1144/gsl.sp.1986.019.01.11",
    number = "1",
    openalex = "W2067877655",
    pages = "203-219",
    volume = "19",
    references = "doi1010160012821x81901898, doi1010160012821x82900073, doi1010160191814180900413, doi101029gd003p0215, doi101038307017a0, doi101126science1894201419, doi10113000917613198210611petian20co2, doi1023071794401, doi102475ajs27511, powell1973plate"
}

— Stratigraphic and petrographic analysis of the Cretaceous to Eocene Tibetan sedimentary succession has allowed us to reinterpret in detail the sequence of events which led to closure of Neotethys and continental collision in the NW Himalaya.During the Early Cretaceous, the Indian passive margin recorded basaltic magmaüc activity. Albian volcanic arenites, probably related to a major extensional tectonic event, are unconformably overlain by an Upper Cretaceous to Paleocene carbonate sequence, with a major quartzarenite episode triggered by the global eustatic sea-level fall at the Cretaceous/Tertiary boundary. At the same time, Neotethyan oceanic crust was being subducted beneath Asia, as testified by calc-alkalic volcanism and forearc basin sedimentation in the Transhimalayan belt.Onset of collision and obduction of the Asian accretionary wedge onto the Indian continental rise was recorded by shoaling of the outer shelf at the Paleocene/Eocene boundary, related to flexural uplift of the passive margin. A few My later, foreland basin volcanic arenites derived from the uplifted Asian subduction complex onlapped onto the Indian continental terrace. All along the Himalaya, marine facies were rapidly replaced by continental redbeds in collisional basins on both sides of the ophiolitic suture. Next, foreland basin sedimentation was interrupted by fold-thrust deformation and final ophiolite emplacement.The observed sequence of events compares favourably with theoretical models of rifted margin to overthrust belt transition and shows that initial phases of continental collision and obduction were completed within 10 to 15 My, with formation of a proto-Himalayan chain by the end of the middle Eocene.

@article{doi10108009853111198711105147,
    author = "Garzanti, Eduardo and Baud, Aymon and Mascle, Georges",
    title = "Sedimentary record of the northward flight of India and its collision with Eurasia (Ladakh Himalaya, India)",
    year = "1987",
    journal = "Geodinamica Acta",
    abstract = "— Stratigraphic and petrographic analysis of the Cretaceous to Eocene Tibetan sedimentary succession has allowed us to reinterpret in detail the sequence of events which led to closure of Neotethys and continental collision in the NW Himalaya.During the Early Cretaceous, the Indian passive margin recorded basaltic magmaüc activity. Albian volcanic arenites, probably related to a major extensional tectonic event, are unconformably overlain by an Upper Cretaceous to Paleocene carbonate sequence, with a major quartzarenite episode triggered by the global eustatic sea-level fall at the Cretaceous/Tertiary boundary. At the same time, Neotethyan oceanic crust was being subducted beneath Asia, as testified by calc-alkalic volcanism and forearc basin sedimentation in the Transhimalayan belt.Onset of collision and obduction of the Asian accretionary wedge onto the Indian continental rise was recorded by shoaling of the outer shelf at the Paleocene/Eocene boundary, related to flexural uplift of the passive margin. A few My later, foreland basin volcanic arenites derived from the uplifted Asian subduction complex onlapped onto the Indian continental terrace. All along the Himalaya, marine facies were rapidly replaced by continental redbeds in collisional basins on both sides of the ophiolitic suture. Next, foreland basin sedimentation was interrupted by fold-thrust deformation and final ophiolite emplacement.The observed sequence of events compares favourably with theoretical models of rifted margin to overthrust belt transition and shows that initial phases of continental collision and obduction were completed within 10 to 15 My, with formation of a proto-Himalayan chain by the end of the middle Eocene.",
    url = "https://doi.org/10.1080/09853111.1987.11105147",
    doi = "10.1080/09853111.1987.11105147",
    openalex = "W2317391324",
    references = "doi1010160012821x85901657"
}

@article{doi10113000167606198798678tcotat20co2,
    author = "Searle, M. P. and Windley, Brian F. and Coward, M. P. and Cooper, David J.W. and Rex, A. J. and Rex, D. C. and Li, Tingdong and Xuchang, Xiao and Jan, M. Q. and Thakur, V. C. and Kumar, Sushil",
    title = "The closing of Tethys and the tectonics of the Himalaya",
    year = "1987",
    journal = "Geological Society of America Bulletin",
    url = "https://doi.org/10.1130/0016-7606(1987)98<678:tcotat>2.0.co;2",
    doi = "10.1130/0016-7606(1987)98<678:tcotat>2.0.co;2",
    openalex = "W2141391066"
}

The stratigraphic and structural features of the Hazara syntaxis are described. A special aim of this work was to integrate modern approaches to rock deformation with the regional tectonics. The region is one of overthrust and shear zone tectonics associated with the development of at least two superimposed sets of major folds and associated minor structures (microfolds, cleavage, vein systems and various types of lineations related to rock strain or intersections of planar structures). It is concluded that the syntaxis results from an early set of nappe units developed by southwestward overthrusting of previously metamorphosed (Himalayan) rocks followed by the formation of a large shear zone structure and finally by the transport of overthrust units from northwest to southeast.

@article{doi101029tc007i002p00273,
    author = "Bossart, Paul and Dietrich, Dorothee and Greco, Antonio and Ottiger, Robert and Ramsay, John G.",
    title = "The tectonic structure of the Hazara‐Kashmir Syntaxis, southern Himalayas, Pakistan",
    year = "1988",
    journal = "Tectonics",
    abstract = "The stratigraphic and structural features of the Hazara syntaxis are described. A special aim of this work was to integrate modern approaches to rock deformation with the regional tectonics. The region is one of overthrust and shear zone tectonics associated with the development of at least two superimposed sets of major folds and associated minor structures (microfolds, cleavage, vein systems and various types of lineations related to rock strain or intersections of planar structures). It is concluded that the syntaxis results from an early set of nappe units developed by southwestward overthrusting of previously metamorphosed (Himalayan) rocks followed by the formation of a large shear zone structure and finally by the transport of overthrust units from northwest to southeast.",
    url = "https://doi.org/10.1029/tc007i002p00273",
    doi = "10.1029/tc007i002p00273",
    openalex = "W2000550147"
}

The hanging wall of the Main Central Thrust (MCT) in Garhwal, India (roughly 79°N–80°E; 30°N–31°N), exhibits an inverted metamorphic gradient: sillimanite ± potassium feldspar assemblages near the top of the hanging wall, or Greater Himalayan sequence, are underlain by kyanite grade rocks near the fault. Textural relationships in pelitic samples from the Alaknanda and Dhauli river valleys indicate that the “inversion” is the product of two distinct metamorphic events: an early Harrovian event (M1), which affected the entire Greater, Himalayan sequence and a later Buchan event (M2), the effects of which are most obvious in the upper part of the sequence. Rim thermobarometry, garnet inclusion thermobarometry, and thermodynamic modeling of garnet zoning reveal that the basal portions of the metamorphic sequence experienced peak M1 conditions of >900 K and >960 MPa (roughly 36 km depth) before following an “erosion controlled” uplift path (e.g., England and Richardson, 1977). M2 metamorphic temperatures in the upper part of the sequence also exceeded 900 K, but maximum pressures (317–523 MPa) indicate paleodepths of only 12–19 km. Calculated pressure‐temperature paths indicate that M2 was characterized by temperature increases of >80 K and roughly 5 km of tectonic burial We attribute M1 to tectonic burial of the Greater Himalayan sequence during the early stages of India‐Eurasia collision. We believe that the uplift and cooling path of the sequence was interrupted in late Oligocene(?) ‐ Miocene time by a second burial and heating event (M2) related to thrust imbrications in southern Tibet. This burial was coincident with the generation of leucogranites, which are abundant near the top of the Greater Himalayan sequence but are virtually absent near the MCT. Field relations do not constrain whether the leucogranites were derived from some presently unexposed portion of the Greater Himalayan sequence and were injected at their present structural level, or were melted in situ. If the granites were injected, then they may have provided some of the heat necessary for M2 metamorphism. Although our data suggest no direct relationship between the Main Central Thrust (as mapped in Garhwal) and metamorphism in the Greater Himalaya, anatectic melting of an unexposed portion of the Greater Himalayan sequence could have been associated with movement along a blind thrust with characteristics similar to the mapped MCT in central Nepal (cf. Le Fort, 1981). If the granites were produced by in situ M2 melting, then we must appeal to a heat source within the upper part of the Greater Himalayan sequence such as locally high concentrations of heat‐producing elements (cf. Pinet and Jaupart, 1987).

@article{doi101029tc007i003p00583,
    author = "Hodges, K. V. and Silverberg, D. S.",
    title = "Thermal evolution of the Greater Himalaya, Garhwal, India",
    year = "1988",
    journal = "Tectonics",
    abstract = "The hanging wall of the Main Central Thrust (MCT) in Garhwal, India (roughly 79°N–80°E; 30°N–31°N), exhibits an inverted metamorphic gradient: sillimanite ± potassium feldspar assemblages near the top of the hanging wall, or Greater Himalayan sequence, are underlain by kyanite grade rocks near the fault. Textural relationships in pelitic samples from the Alaknanda and Dhauli river valleys indicate that the “inversion” is the product of two distinct metamorphic events: an early Harrovian event (M1), which affected the entire Greater, Himalayan sequence and a later Buchan event (M2), the effects of which are most obvious in the upper part of the sequence. Rim thermobarometry, garnet inclusion thermobarometry, and thermodynamic modeling of garnet zoning reveal that the basal portions of the metamorphic sequence experienced peak M1 conditions of >900 K and >960 MPa (roughly 36 km depth) before following an “erosion controlled” uplift path (e.g., England and Richardson, 1977). M2 metamorphic temperatures in the upper part of the sequence also exceeded 900 K, but maximum pressures (317–523 MPa) indicate paleodepths of only 12–19 km. Calculated pressure‐temperature paths indicate that M2 was characterized by temperature increases of >80 K and roughly 5 km of tectonic burial We attribute M1 to tectonic burial of the Greater Himalayan sequence during the early stages of India‐Eurasia collision. We believe that the uplift and cooling path of the sequence was interrupted in late Oligocene(?) ‐ Miocene time by a second burial and heating event (M2) related to thrust imbrications in southern Tibet. This burial was coincident with the generation of leucogranites, which are abundant near the top of the Greater Himalayan sequence but are virtually absent near the MCT. Field relations do not constrain whether the leucogranites were derived from some presently unexposed portion of the Greater Himalayan sequence and were injected at their present structural level, or were melted in situ. If the granites were injected, then they may have provided some of the heat necessary for M2 metamorphism. Although our data suggest no direct relationship between the Main Central Thrust (as mapped in Garhwal) and metamorphism in the Greater Himalaya, anatectic melting of an unexposed portion of the Greater Himalayan sequence could have been associated with movement along a blind thrust with characteristics similar to the mapped MCT in central Nepal (cf. Le Fort, 1981). If the granites were produced by in situ M2 melting, then we must appeal to a heat source within the upper part of the Greater Himalayan sequence such as locally high concentrations of heat‐producing elements (cf. Pinet and Jaupart, 1987).",
    url = "https://doi.org/10.1029/tc007i003p00583",
    doi = "10.1029/tc007i003p00583",
    openalex = "W2143412241"
}

Abstract The collision of the Indian Plate with the Karakoram-Lhasa Blocks and the closing of Neo-Tethys along the Indus Suture Zone (ISZ) is well constrained by sedimentologic, structural and palaeomagnetic data at ca. 50 Ma. Pre-collision high P— low T blueschist facies metamorphism in the ISZ is related to subduction of Tethyan oceanic crust northwards beneath the Jurassic-early Cretaceous Dras island arc. The Spontang ophiolite was obducted south westwards onto the Zanskar shelf before the Eocene closure (Dl). The youngest marine sediments on the Zanskar shelf and along the ISZ are Lower Eocene, after which continental molasse deposition occurred. After ocean closure, thrusting followed a SW-directed piggy-back sequence (D2). This has been modified by late-stage breakback thrusts, overturned thrusts and extensional normal faulting associated with culmination collapse and underplating. The ISZ and northern Zanskar shelf sequence are affected by late Tertiary redirected backthrusting (D3), which also affects the Indus molasse. A 50 km wide ‘pop-up’ zone with divergent thrust vergence was developed across the Zanskar Range. Balanced and restored cross sections indicate a minimum of 150 km of shortening across the Zanskar shelf and ISZ. Post-collision crustal thickening by thrust stacking resulted in widespread Barrovian metamorphism in the High Himalaya that reached a thermal climax during Oligocene-Miocene times. Garnet-biotite-muscovite + tourmaline granites were generated by intracrustal partial melting during the Miocene within the Central Crystalline Complex. Their emplacement on the hangingwall of localized ductile shear zones was associated with SW-directed thrusting along the Main Central Thrust (MCT) zone and concomitant culmination collapse normal faulting along the Zanskar Shear Zone (ZSZ) at the top of the slab. Metamorphic isograds have become inverted by post-metamorphic SW-verging recumbent folding and thrusting along the base of the High Himalayan slab. Along the top of the slab, isograds are the right way up but are structurally and thermally telescoped by normal faulting along the ZSZ. 1

@article{doi101098rsta19880082,
    author = "Searle, M. P. and Cooper, David J.W. and Rex, A. J. and Colchen, M.",
    title = "Collision tectonics of the Ladakh-Zanskar Himalaya",
    year = "1988",
    journal = "Philosophical Transactions of the Royal Society of London Series A Mathematical and Physical Sciences",
    abstract = "Abstract The collision of the Indian Plate with the Karakoram-Lhasa Blocks and the closing of Neo-Tethys along the Indus Suture Zone (ISZ) is well constrained by sedimentologic, structural and palaeomagnetic data at ca. 50 Ma. Pre-collision high P— low T blueschist facies metamorphism in the ISZ is related to subduction of Tethyan oceanic crust northwards beneath the Jurassic-early Cretaceous Dras island arc. The Spontang ophiolite was obducted south westwards onto the Zanskar shelf before the Eocene closure (Dl). The youngest marine sediments on the Zanskar shelf and along the ISZ are Lower Eocene, after which continental molasse deposition occurred. After ocean closure, thrusting followed a SW-directed piggy-back sequence (D2). This has been modified by late-stage breakback thrusts, overturned thrusts and extensional normal faulting associated with culmination collapse and underplating. The ISZ and northern Zanskar shelf sequence are affected by late Tertiary redirected backthrusting (D3), which also affects the Indus molasse. A 50 km wide ‘pop-up’ zone with divergent thrust vergence was developed across the Zanskar Range. Balanced and restored cross sections indicate a minimum of 150 km of shortening across the Zanskar shelf and ISZ. Post-collision crustal thickening by thrust stacking resulted in widespread Barrovian metamorphism in the High Himalaya that reached a thermal climax during Oligocene-Miocene times. Garnet-biotite-muscovite + tourmaline granites were generated by intracrustal partial melting during the Miocene within the Central Crystalline Complex. Their emplacement on the hangingwall of localized ductile shear zones was associated with SW-directed thrusting along the Main Central Thrust (MCT) zone and concomitant culmination collapse normal faulting along the Zanskar Shear Zone (ZSZ) at the top of the slab. Metamorphic isograds have become inverted by post-metamorphic SW-verging recumbent folding and thrusting along the base of the High Himalayan slab. Along the top of the slab, isograds are the right way up but are structurally and thermally telescoped by normal faulting along the ZSZ. 1",
    url = "https://doi.org/10.1098/rsta.1988.0082",
    doi = "10.1098/rsta.1988.0082",
    openalex = "W1963662898"
}

Abstract The Tibetan Plateau, between the Kunlun Shan and the Himalayas, consists of terranes accreted successively to Eurasia. The northernmost, the Songban Ganzi Terrane, was accreted to the Kunlun (Tarim-North China Terrane) along the Kunlun-Qinling Suture during the late Permian. The Qiangtang Terrane accreted to the Songban-Ganzi along the Jinsha Suture during the late Triassic or earliest Jurassic, the Lhasa Terrane to the Qiangtang along the Banggong Suture during the late Jurassic and, finally, Peninsular India to the Lhasa Terrane along the Zangbo Suture during the Middle Eocene. The Kunlun Shan, Qiangtang and Lhasa Terranes are all underlain by Precambrian continental crust at least a billion years old. The Qiangtang and Lhasa Terranes came from Gondwanaland. Substantial southward ophiolite obduction occurred across the Lhasa Terrane from the Banggong Suture in the late Jurassic and from the Zangbo Suture in the latest Cretaceous-earliest Palaeocene. Palaeomagnetic data suggest successive wide Palaeotethyan oceans during the late Palaeozoic and early Mesozoic and a Neotethys which was at least 6000 km wide during the mid-Cretaceous. Thickening of the Tibetan crust to almost double the normal thickness occurred by northward-migrating north-south shortening and vertical stretching during the mid-Eocene to earliest Miocene indentation of Asia by India; Neogene strata are almost flat-lying and rest unconformably upon Palaeogene or older strata. Since the early Miocene, the northward motion of India has been accommodated principally by north south shortening both north and south of Tibet. From early Pliocene to the Present, the Tibetan Plateau has risen by about two kilometres and has suffered east-west extension. Little, if any, of the India Eurasia convergence has been accommodated by eastward lateral extrusion.

@article{doi101098rsta19880135,
    author = "Dewey, John and SHACKLETON, R. and Chengfa, Chang and Yiyin, Sun",
    title = "The tectonic evolution of the Tibetan Plateau",
    year = "1988",
    journal = "Philosophical Transactions of the Royal Society of London Series A Mathematical and Physical Sciences",
    abstract = "Abstract The Tibetan Plateau, between the Kunlun Shan and the Himalayas, consists of terranes accreted successively to Eurasia. The northernmost, the Songban Ganzi Terrane, was accreted to the Kunlun (Tarim-North China Terrane) along the Kunlun-Qinling Suture during the late Permian. The Qiangtang Terrane accreted to the Songban-Ganzi along the Jinsha Suture during the late Triassic or earliest Jurassic, the Lhasa Terrane to the Qiangtang along the Banggong Suture during the late Jurassic and, finally, Peninsular India to the Lhasa Terrane along the Zangbo Suture during the Middle Eocene. The Kunlun Shan, Qiangtang and Lhasa Terranes are all underlain by Precambrian continental crust at least a billion years old. The Qiangtang and Lhasa Terranes came from Gondwanaland. Substantial southward ophiolite obduction occurred across the Lhasa Terrane from the Banggong Suture in the late Jurassic and from the Zangbo Suture in the latest Cretaceous-earliest Palaeocene. Palaeomagnetic data suggest successive wide Palaeotethyan oceans during the late Palaeozoic and early Mesozoic and a Neotethys which was at least 6000 km wide during the mid-Cretaceous. Thickening of the Tibetan crust to almost double the normal thickness occurred by northward-migrating north-south shortening and vertical stretching during the mid-Eocene to earliest Miocene indentation of Asia by India; Neogene strata are almost flat-lying and rest unconformably upon Palaeogene or older strata. Since the early Miocene, the northward motion of India has been accommodated principally by north south shortening both north and south of Tibet. From early Pliocene to the Present, the Tibetan Plateau has risen by about two kilometres and has suffered east-west extension. Little, if any, of the India Eurasia convergence has been accommodated by eastward lateral extrusion.",
    url = "https://doi.org/10.1098/rsta.1988.0135",
    doi = "10.1098/rsta.1988.0135",
    openalex = "W2016760315",
    references = "crossref1974the, doi101029jb075i014p02625, doi101029jb083ib10p04975, doi101038211676a0, doi101038279590a0, doi101144transed83387, doi102475ajs27511"
}

@misc{crossref1989tectonics,
    title = "Tectonics of the western Himalayas",
    year = "1989",
    url = "https://doi.org/10.1130/spe232",
    doi = "10.1130/spe232",
    openalex = "W632126003"
}

@misc{malinconico1989tectonics1,
    author = "Malinconico, L. L. and Jr., Lillie and J, R.",
    title = "Tectonics of the Western Himalayas, 232 of GSA Special Paper",
    year = "1989",
    howpublished = "Boulder, Colorado, Geological Society of America, 320 p",
    note = "talkorigins\_source = {true}; raw\_reference = {Malinconico, L. L., Jr., and Lillie, R. J., 1989, Tectonics of the Western Himalayas, 232 of GSA Special Paper: Boulder, Colorado, Geological Society of America, 320 p.}"
}

Source parameters of 53 moderate‐sized earthquakes, obtained from the joint inversion of regional and teleseismic distance long‐period body waves, provide the data set for an analysis of the style of deformation and kinematics in the region of the Eastern Himalayan Syntaxis. Focal mechanisms of Eastern Himalayan events show oblique thrust, consistent with the N‐NE directed movement of the Indian plate as it underthrusts a boundary that strikes at an oblique angle to the direction of convergence. Earthquakes near the Sagaing fault show strike‐slip mechanisms with right‐lateral slip. Earthquakes on its northern splays, however, indicate predominant thrusting, evidence that the dextral motion on the Sagaing fault, which accommodates a portion of the lateral motion between India and southeast Asia, terminates in a zone of thrust faulting at the Eastern Himalayan Syntaxis. Remaining motion between India and southeast Asia is accommodated in a zone of distributed shear in east Burma and Yunnan, manifested by strike‐slip and oblique normal faulting, east‐west extension, crustal thinning, and clockwise rotation of crustal blocks. We determined strain rates throughout the region with a moment tensor summation using 25 years (modern) and 85 years (modern and historic) of earthquake data. We matched the observed strains with a fifth‐order polynomial function, and from this we determined both the velocity field and rotations with respect to a specified region. Velocities calculated relative to south China stationary show that the entire area, extending from 20°N–36°N, within deforming Asia (Yunnan, western Sichuan, and east Tibet), constitutes a distributed dextral shear zone with clockwise rotations up to 1.7°/m.y., maximum in the region of the Eastern Syntaxis proper. Integrated strains across this zone, relative to south China stationary, show 38 mm/yr ± 12mm/yr of north‐directed motion at the Himalaya. Remaining plate motion, relative to south China fixed, must be taken up by the underthrusting of India beneath the lesser Himalaya, strike‐slip motion on the Sagaing fault, and intraplate NE directed shortening within NE India as well as NE directed shortening within the Eastern Syntaxis proper. 10 mm/yr ± 2 mm/yr of relative right‐lateral motion between India and southeast Asia is absorbed in the region between the Sagaing and Red River faults (94°E–100°E). It is the clockwise vorticity (relative to south China) associated with the deformation in Yunnan, east Tibet, and western Sichuan that provides the relative north‐directed motion of 38 ± 12 mm/yr at the Himalaya. Not all of the deformation is accommodated in right‐lateral shear between India and south China and between east Tibet and south China; velocity gradients exist that are parallel to the trend of the shear zone. Relative to a point within western Sichuan (32°N, 100°E), the velocity field shows that the Yunnan crust is moving S‐SE at rates of 8–10 mm/yr. Relative to south China, there is no eastward expulsion of crustal material beyond the eastern margin of the Tibetan plateau.

@article{doi10102991jb01021,
    author = "Holt, W. E. and Ni, James and Wallace, Terry C. and Haines, A. J.",
    title = "The active tectonics of the eastern Himalayan syntaxis and surrounding regions",
    year = "1991",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "Source parameters of 53 moderate‐sized earthquakes, obtained from the joint inversion of regional and teleseismic distance long‐period body waves, provide the data set for an analysis of the style of deformation and kinematics in the region of the Eastern Himalayan Syntaxis. Focal mechanisms of Eastern Himalayan events show oblique thrust, consistent with the N‐NE directed movement of the Indian plate as it underthrusts a boundary that strikes at an oblique angle to the direction of convergence. Earthquakes near the Sagaing fault show strike‐slip mechanisms with right‐lateral slip. Earthquakes on its northern splays, however, indicate predominant thrusting, evidence that the dextral motion on the Sagaing fault, which accommodates a portion of the lateral motion between India and southeast Asia, terminates in a zone of thrust faulting at the Eastern Himalayan Syntaxis. Remaining motion between India and southeast Asia is accommodated in a zone of distributed shear in east Burma and Yunnan, manifested by strike‐slip and oblique normal faulting, east‐west extension, crustal thinning, and clockwise rotation of crustal blocks. We determined strain rates throughout the region with a moment tensor summation using 25 years (modern) and 85 years (modern and historic) of earthquake data. We matched the observed strains with a fifth‐order polynomial function, and from this we determined both the velocity field and rotations with respect to a specified region. Velocities calculated relative to south China stationary show that the entire area, extending from 20°N–36°N, within deforming Asia (Yunnan, western Sichuan, and east Tibet), constitutes a distributed dextral shear zone with clockwise rotations up to 1.7°/m.y., maximum in the region of the Eastern Syntaxis proper. Integrated strains across this zone, relative to south China stationary, show 38 mm/yr ± 12mm/yr of north‐directed motion at the Himalaya. Remaining plate motion, relative to south China fixed, must be taken up by the underthrusting of India beneath the lesser Himalaya, strike‐slip motion on the Sagaing fault, and intraplate NE directed shortening within NE India as well as NE directed shortening within the Eastern Syntaxis proper. 10 mm/yr ± 2 mm/yr of relative right‐lateral motion between India and southeast Asia is absorbed in the region between the Sagaing and Red River faults (94°E–100°E). It is the clockwise vorticity (relative to south China) associated with the deformation in Yunnan, east Tibet, and western Sichuan that provides the relative north‐directed motion of 38 ± 12 mm/yr at the Himalaya. Not all of the deformation is accommodated in right‐lateral shear between India and south China and between east Tibet and south China; velocity gradients exist that are parallel to the trend of the shear zone. Relative to a point within western Sichuan (32°N, 100°E), the velocity field shows that the Yunnan crust is moving S‐SE at rates of 8–10 mm/yr. Relative to south China, there is no eastward expulsion of crustal material beyond the eastern margin of the Tibetan plateau.",
    url = "https://doi.org/10.1029/91jb01021",
    doi = "10.1029/91jb01021",
    openalex = "W2025580382",
    references = "doi101016004019517690069x"
}

Balanced and restored structural sections across the far‐eastern Nepal Himalaya have been constructed in order to determine the structure and evolution of the Himalayan orogenic wedge and the amount of tectonic shortening the region has undergone since the initiation of thrusting along the Main Central Thrust (MCT). The far‐eastern Nepal Himalaya is comprised of three distinct, thrust‐bound tectonic packages; the Higher Himalayan (Crystalline) thrust sheet, the Lesser Himalayan (Metasediment) thrust package, and the Sub‐Himalayan imbricate fan. The Higher Himalayan Crystallines, consisting of kyanite‐ and sillimanite‐bearing gneisses intruded by the Miocene (?) Jannu leucogranites, have been thrust over the Lesser Himalayan Metasediments along the MCT for a distance of 140 km to 175 km. The Lesser Himalayan Metasediments are a 12 km thick unit consisting primarily of phyllites, metaquartzites, and mylonitic augen gneisses in which garnet, biotite and chlorite metamorphic zones are exposed in progressively deeper structural levels. The Lesser Himalayan (Metasediment) thrust package is underlain by a decollement, the Main Detachment Fault (MDF), which lies at a calculated depth of between 6 and 10 km underneath the Mahabharat Lekh, and at a calculated depth of 20 to 25 km north of the Tamar Khola Dome. The Tamar Khola Dome overlies a footwall ramp along the MDF where the MDF cuts upsection through the Lesser Himalayan Metasediments. The Lesser Himalayan thrust package probably has an internal structure aproximating a hinterland‐dipping duplex, with the MCT and the MDF corresponding to the roof and floor thrusts, respectively. Both the Tamar Khola Thrust, an out‐of‐sequence breach thrust, and the Main Boundary Thrust (MBT) are splay thrusts off of the MDF. The Sub‐Himalaya, consisting of nonmetamorphosed sedimentary rocks, displays an emergent imbricate fan geometry and is underlain by the southern continuation of the MDF which lies at a depth of 5.5 km to 6 km beneath the Siwalik Hills. Folding and thrusting within the Lesser Himalayan thrust package and the Sub‐Himalayan imbricate fan have accomodated 45 to 70 km of tectonic shortening. Total north‐south shortening across the Higher, Lesser, and Sub‐Himalaya of far‐eastern Nepal, south of the Tibetan Plateau, has been of the order of 185 km to 245 km and has occurred at an average rate of 7.4 mm to 15.3 mm per year since the initiation of the MCT between 16 and 25 Ma.

@article{doi10102991tc01011,
    author = "Schelling, Daniel and Arita, Kazunori",
    title = "Thrust tectonics, crustal shortening, and the structure of the far‐eastern Nepal Himalaya",
    year = "1991",
    journal = "Tectonics",
    abstract = "Balanced and restored structural sections across the far‐eastern Nepal Himalaya have been constructed in order to determine the structure and evolution of the Himalayan orogenic wedge and the amount of tectonic shortening the region has undergone since the initiation of thrusting along the Main Central Thrust (MCT). The far‐eastern Nepal Himalaya is comprised of three distinct, thrust‐bound tectonic packages; the Higher Himalayan (Crystalline) thrust sheet, the Lesser Himalayan (Metasediment) thrust package, and the Sub‐Himalayan imbricate fan. The Higher Himalayan Crystallines, consisting of kyanite‐ and sillimanite‐bearing gneisses intruded by the Miocene (?) Jannu leucogranites, have been thrust over the Lesser Himalayan Metasediments along the MCT for a distance of 140 km to 175 km. The Lesser Himalayan Metasediments are a 12 km thick unit consisting primarily of phyllites, metaquartzites, and mylonitic augen gneisses in which garnet, biotite and chlorite metamorphic zones are exposed in progressively deeper structural levels. The Lesser Himalayan (Metasediment) thrust package is underlain by a decollement, the Main Detachment Fault (MDF), which lies at a calculated depth of between 6 and 10 km underneath the Mahabharat Lekh, and at a calculated depth of 20 to 25 km north of the Tamar Khola Dome. The Tamar Khola Dome overlies a footwall ramp along the MDF where the MDF cuts upsection through the Lesser Himalayan Metasediments. The Lesser Himalayan thrust package probably has an internal structure aproximating a hinterland‐dipping duplex, with the MCT and the MDF corresponding to the roof and floor thrusts, respectively. Both the Tamar Khola Thrust, an out‐of‐sequence breach thrust, and the Main Boundary Thrust (MBT) are splay thrusts off of the MDF. The Sub‐Himalaya, consisting of nonmetamorphosed sedimentary rocks, displays an emergent imbricate fan geometry and is underlain by the southern continuation of the MDF which lies at a depth of 5.5 km to 6 km beneath the Siwalik Hills. Folding and thrusting within the Lesser Himalayan thrust package and the Sub‐Himalayan imbricate fan have accomodated 45 to 70 km of tectonic shortening. Total north‐south shortening across the Higher, Lesser, and Sub‐Himalaya of far‐eastern Nepal, south of the Tibetan Plateau, has been of the order of 185 km to 245 km and has occurred at an average rate of 7.4 mm to 15.3 mm per year since the initiation of the MCT between 16 and 25 Ma.",
    url = "https://doi.org/10.1029/91tc01011",
    doi = "10.1029/91tc01011",
    openalex = "W2138724462",
    references = "doi101007bf01823808"
}

ABSTRACT The geologic evolution of northern India is best recorded in the stratigraphic succession of the Zanskar Range (northwestern Himalaya), which represents the most complete transect through this ancient continental margin. Sedimentary history began in the late Proterozoic, and recorded a late Pan-African orogenic event around the Cambrian-Ordovician boundary, when the Gondwana supercontinent was eventually assembled. The following long period of epicontinental deposition in shallow seas linked to palaeo-Tethys lasted until the Early Permian, when a neo-Tethyan rift began to open between paleo-India and the Cimmerian microcontinents. Neo-Tethyan history can be subdivided into two sedimentary megasequences, both recording a major tectonic and magmatic event in the lower part. The first one began with breakup in the Late Permian and lasted until the end of the Jurassic. The second one started in the Early Cretaceous with the final detachment of India from Gondwana and the opening of the Indian Ocean, and ended with the India-Eurasia collision in the Early Eocene. The two megasequences can be in turn subdivided into six transgressive/regressive supersequences bounded by tectonically enhanced unconformities. Basal sandstone units of Early Permian, Late Permian, Norian, Callovian, Early Cretaceous, and Paleocene age are invariably associated with oolitic ironstones or reworked glauco-phosphorites, and mark the transgressive part of each supersequence. Next, condensed nodular carbonates or shales with pelagic fauna are typically overlain by thick shallowing-upward marly units capped by regressive platformal carbonates. The six tectono-eustatic supercycles reflect successive rifting episodes which punctuated the progressive separation of India from the rest of Gondwana, and document the combination of plate/microplate reorganizations and eustatic, climatic, and oceanographic changes in the Tethyan domain. After the onset of collision between India and Asia close to the Paleocene/Eocene boundary, obduction of the remnants of the neo-Tethys ocean floor onto the Indian margin began, and the latter underwent multiphase deformation with fold-thrust shortening followed by heating and extension. After the main metamorphic event, ophiolitic nappes were re-thrusted and finally emplaced with their sedimentary sole on top of the passive-margin succession.

@article{doi1013060c9b2957171011d78645000102c1865d,
    author = "Gaetani, Maurizio and Garzanti, Eduardo",
    title = "Multicyclic History of the Northern India Continental Margin (Northwestern Himalaya)",
    year = "1991",
    journal = "AAPG Bulletin",
    abstract = "ABSTRACT The geologic evolution of northern India is best recorded in the stratigraphic succession of the Zanskar Range (northwestern Himalaya), which represents the most complete transect through this ancient continental margin. Sedimentary history began in the late Proterozoic, and recorded a late Pan-African orogenic event around the Cambrian-Ordovician boundary, when the Gondwana supercontinent was eventually assembled. The following long period of epicontinental deposition in shallow seas linked to palaeo-Tethys lasted until the Early Permian, when a neo-Tethyan rift began to open between paleo-India and the Cimmerian microcontinents. Neo-Tethyan history can be subdivided into two sedimentary megasequences, both recording a major tectonic and magmatic event in the lower part. The first one began with breakup in the Late Permian and lasted until the end of the Jurassic. The second one started in the Early Cretaceous with the final detachment of India from Gondwana and the opening of the Indian Ocean, and ended with the India-Eurasia collision in the Early Eocene. The two megasequences can be in turn subdivided into six transgressive/regressive supersequences bounded by tectonically enhanced unconformities. Basal sandstone units of Early Permian, Late Permian, Norian, Callovian, Early Cretaceous, and Paleocene age are invariably associated with oolitic ironstones or reworked glauco-phosphorites, and mark the transgressive part of each supersequence. Next, condensed nodular carbonates or shales with pelagic fauna are typically overlain by thick shallowing-upward marly units capped by regressive platformal carbonates. The six tectono-eustatic supercycles reflect successive rifting episodes which punctuated the progressive separation of India from the rest of Gondwana, and document the combination of plate/microplate reorganizations and eustatic, climatic, and oceanographic changes in the Tethyan domain. After the onset of collision between India and Asia close to the Paleocene/Eocene boundary, obduction of the remnants of the neo-Tethys ocean floor onto the Indian margin began, and the latter underwent multiphase deformation with fold-thrust shortening followed by heating and extension. After the main metamorphic event, ophiolitic nappes were re-thrusted and finally emplaced with their sedimentary sole on top of the passive-margin succession.",
    url = "https://doi.org/10.1306/0c9b2957-1710-11d7-8645000102c1865d",
    doi = "10.1306/0c9b2957-1710-11d7-8645000102c1865d",
    openalex = "W2140845599"
}

Six years of geological research in eastern Nepal has resulted in a new geological map of the eastern Nepal Himalaya which includes the region stretching from the Sikkhim border in the east to the Kathmandu Valley in the west, and from the summits of the Higher Himalaya in the north to the Ganges Plain in the south. This research has permitted the determination of the tectonostratigraphy and structure of one section of the central Himalayan arc. South of the Tibetan Plateau the eastern Nepal Himalaya can be divided into three distinct, thrust‐bound tectonic packages: (1) the Higher Himalayan thrust sheet composed of the Higher Himalayan Crystallines, (2) the Lesser Himalayan thrust sheet composed of the Lesser Himalayan Series, and (3) the Sub‐Himalayan imbricate zone composed of sedimentary rocks belonging to the Siwalik Group. The Higher Himalayan thrust sheet of eastern Nepal has been thrust over the Lesser Himalayan Metasediments a minimum of 140 km, and possibly as much as 175–210 km, along the Main Central Thrust (MCT). The Lesser Himalayan thrust sheet is overlain by the MCT and is underlain by the Main Detachment Fault (MDF) and the Main Boundary Thrust (MBT). Out‐of‐sequence thrust faults in the hanging wall of the MBT have breached and offset the presently inactive MCT. The Sub‐Himalayan imbricate zone is an emergent imbricate fan bounded by the MBT to the north and the Main Frontal Thrust (MFT) to the south and is underlain by the MDF which lies at a depth of between 5 km and 7 km. A balanced cross section constructed across the Higher, Lesser, and Sub‐Himalaya of eastern Nepal shows that the eastern Nepal Himalayan orogenic wedge has undergone a minimum of between 210 and 280 km of horizontal, north‐south tectonic shortening since the initiation of the MCT. The Lesser and Sub‐Himalaya have absorbed 70 km of north‐south shortening by thrusting along the basal MDF, of which the Sub‐Himalayan imbricate zone has accommodated 25 km, the Sun Kosi Thrust has accommodated about 10 km, and the MBT has accommodated the remaining 35 km of shortening. Since the initiation of the MCT between 15 Ma and 25 Ma shortening across the eastern Nepal Himalaya has occurred at an average rate of 8.4–18.6 mm per year. The structural geometry of the eastern Nepal Himalaya suggests an overall “piggyback” sequence of thrusting, with motion transferred from the MCT to the underlying MDF and its emergent splay thrust, the MBT, and with the MBT rotated to its present steep orientation by imbricate thrusting within the Sub‐Himalaya.

@article{doi10102992tc00213,
    author = "Schelling, Daniel",
    title = "The tectonostratigraphy and structure of the eastern Nepal Himalaya",
    year = "1992",
    journal = "Tectonics",
    abstract = "Six years of geological research in eastern Nepal has resulted in a new geological map of the eastern Nepal Himalaya which includes the region stretching from the Sikkhim border in the east to the Kathmandu Valley in the west, and from the summits of the Higher Himalaya in the north to the Ganges Plain in the south. This research has permitted the determination of the tectonostratigraphy and structure of one section of the central Himalayan arc. South of the Tibetan Plateau the eastern Nepal Himalaya can be divided into three distinct, thrust‐bound tectonic packages: (1) the Higher Himalayan thrust sheet composed of the Higher Himalayan Crystallines, (2) the Lesser Himalayan thrust sheet composed of the Lesser Himalayan Series, and (3) the Sub‐Himalayan imbricate zone composed of sedimentary rocks belonging to the Siwalik Group. The Higher Himalayan thrust sheet of eastern Nepal has been thrust over the Lesser Himalayan Metasediments a minimum of 140 km, and possibly as much as 175–210 km, along the Main Central Thrust (MCT). The Lesser Himalayan thrust sheet is overlain by the MCT and is underlain by the Main Detachment Fault (MDF) and the Main Boundary Thrust (MBT). Out‐of‐sequence thrust faults in the hanging wall of the MBT have breached and offset the presently inactive MCT. The Sub‐Himalayan imbricate zone is an emergent imbricate fan bounded by the MBT to the north and the Main Frontal Thrust (MFT) to the south and is underlain by the MDF which lies at a depth of between 5 km and 7 km. A balanced cross section constructed across the Higher, Lesser, and Sub‐Himalaya of eastern Nepal shows that the eastern Nepal Himalayan orogenic wedge has undergone a minimum of between 210 and 280 km of horizontal, north‐south tectonic shortening since the initiation of the MCT. The Lesser and Sub‐Himalaya have absorbed 70 km of north‐south shortening by thrusting along the basal MDF, of which the Sub‐Himalayan imbricate zone has accommodated 25 km, the Sun Kosi Thrust has accommodated about 10 km, and the MBT has accommodated the remaining 35 km of shortening. Since the initiation of the MCT between 15 Ma and 25 Ma shortening across the eastern Nepal Himalaya has occurred at an average rate of 8.4–18.6 mm per year. The structural geometry of the eastern Nepal Himalaya suggests an overall “piggyback” sequence of thrusting, with motion transferred from the MCT to the underlying MDF and its emergent splay thrust, the MBT, and with the MBT rotated to its present steep orientation by imbricate thrusting within the Sub‐Himalaya.",
    url = "https://doi.org/10.1029/92tc00213",
    doi = "10.1029/92tc00213",
    openalex = "W2130840441",
    references = "doi101007bf01823808"
}

Analysis of data from 280 rivers discharging to the ocean indicates that sediment loads/yields are a log-linear function of basin area and maximum elevation of the river basin. Other factors controlling sediment discharge (e.g., climate, runoff) appear to have secondary importance. A notable exception is the influence of human activity, climate, and geology on the rivers draining southern Asia and Oceania. Sediment fluxes from small mountainous rivers, many of which discharge directly onto active margins (e.g., western South and North America and most high-standing oceanic islands), have been greatly underestimated in previous global sediment budgets, perhaps by as much as a factor of three. In contrast, sediment fluxes to the ocean from large rivers (nearly all of which discharge onto passive margins or marginal seas) have been overestimated, as some of the sediment load is subaerially sequestered in subsiding deltas. Before the proliferation of dam construction in the latter half of this century, rivers probably discharged about 20 billion tons of sediment annually to the ocean. Prior to widespread farming and deforestation (beginning 2000-2500 yr ago), however, sediment discharge probably was less than half the present level. Sediments discharged by small mountainous rivers are more likely to escape to the deep sea during high stands of sea level by virtue of a greater impact of episodic events (i.e., flash floods and earthquakes) on small drainage basins and because of the narrow shelves associated with active margins. The resulting delta/fan deposits can be distinctly different than the sedimentary deposits derived from larger rivers that discharge onto passive margins.

@article{doi101086629606,
    author = "Milliman, John D. and Syvitski, James P. M.",
    title = "Geomorphic/Tectonic Control of Sediment Discharge to the Ocean: The Importance of Small Mountainous Rivers",
    year = "1992",
    journal = "The Journal of Geology",
    abstract = "Analysis of data from 280 rivers discharging to the ocean indicates that sediment loads/yields are a log-linear function of basin area and maximum elevation of the river basin. Other factors controlling sediment discharge (e.g., climate, runoff) appear to have secondary importance. A notable exception is the influence of human activity, climate, and geology on the rivers draining southern Asia and Oceania. Sediment fluxes from small mountainous rivers, many of which discharge directly onto active margins (e.g., western South and North America and most high-standing oceanic islands), have been greatly underestimated in previous global sediment budgets, perhaps by as much as a factor of three. In contrast, sediment fluxes to the ocean from large rivers (nearly all of which discharge onto passive margins or marginal seas) have been overestimated, as some of the sediment load is subaerially sequestered in subsiding deltas. Before the proliferation of dam construction in the latter half of this century, rivers probably discharged about 20 billion tons of sediment annually to the ocean. Prior to widespread farming and deforestation (beginning 2000-2500 yr ago), however, sediment discharge probably was less than half the present level. Sediments discharged by small mountainous rivers are more likely to escape to the deep sea during high stands of sea level by virtue of a greater impact of episodic events (i.e., flash floods and earthquakes) on small drainage basins and because of the narrow shelves associated with active margins. The resulting delta/fan deposits can be distinctly different than the sedimentary deposits derived from larger rivers that discharge onto passive margins.",
    url = "https://doi.org/10.1086/629606",
    doi = "10.1086/629606",
    openalex = "W2026886308",
    references = "doi10100797814612378841, doi10102991rg00969, doi101029tr039i006p01076, doi101029wr004i004p00737, doi101086628741, doi101126science2284698488, doi101126science23547931156, doi101130001676061967781203tgotar20co2, doi102307635458, doi102475ajs2683243, openalexw2338892475"
}

We present the interpretation of a new set of closely spaced marine magnetic profiles that complements previous data in the northeastern and southwestern parts of the South China Sea (Nan Hai). This interpretation shows that seafloor spreading was asymmetric and confirms that it included at least one ridge jump. Discontinuities in the seafloor fabric, characterized by large differences in basement depth and roughness, appear to be related to variations in spreading rate. Between anomalies 11 and 7 (32 to 27 Ma), spreading at an intermediate, average full rate of ≈50 mm/yr created relatively smooth basement, now thickly blanketed by sediments. The ridge then jumped to the south and created rough basement, now much shallower and covered with thinner sediments than in the north. This episode lasted from anomaly 6b to anomaly 5c (27 to ≈16 Ma) and the average spreading rate was slower, ≈35 mm/yr. After 27 Ma, spreading appears to have developed first in the eastern part of the basin and to have propagated towards the southwest in two major steps, at the time of anomalies 6b‐7, and at the time of anomaly 6. Each step correlates with a variation of the ridge orientation, from nearly E‐W to NE‐SW, and with a variation in the spreading rate. Spreading appears to have stopped synchronously along the ridge, at about 15.5 Ma. From computed fits of magnetic isochrons, we calculate 10 poles of finite rotation between the times of magnetic anomalies 11 and 5c. The poles permit reconstruction of the Oligo‐Miocene movements of Southeast Asian blocks north and south of the South China Sea. Using such reconstructions, we test quantitatively a simple scenario for the opening of the sea in which seafloor spreading results from the extrusion of Indochina relative to South China, in response to the penetration of India into Asia. This alone yields between 500 and 600 km of left‐lateral motion on the Red River‐Ailao Shan shear zone, with crustal shortening in the San Jiang region and crustal extension in Tonkin. The offset derived from the fit of magnetic isochrons on the South China Sea floor is compatible with the offset of geological markers north and south of the Red River Zone. The first phases of extension of the continental margins of the basin are probably related to motion on the Wang Chao and Three Pagodas Faults, in addition to the Red River Fault. That Indochina rotated at least 12° relative to South China implies that large‐scale “domino” models are inadequate to describe the Cenozoic tectonics of Southeast Asia. The cessation of spreading after 16 Ma appears to be roughly synchronous with the final increments of left‐lateral shear and normal uplift in the Ailao Shan (18 Ma), as well as with incipient collisions between the Australian and the Eurasian plates. Hence no other causes than the activation of new fault zones within the India‐Asia collision zone, north and east of the Red River Fault, and perhaps increased resistance to extrusion along the SE edge of Sundaland, appear to be required to terminate seafloor spreading in the largest marginal basin of the western Pacific and to change the sense of motion on the largest strike‐slip fault of SE Asia.

@article{doi10102992jb02280,
    author = "Briais, A. and Patriat, Philippe and Tapponnier, Paul",
    title = "Updated interpretation of magnetic anomalies and seafloor spreading stages in the south China Sea: Implications for the Tertiary tectonics of Southeast Asia",
    year = "1993",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "We present the interpretation of a new set of closely spaced marine magnetic profiles that complements previous data in the northeastern and southwestern parts of the South China Sea (Nan Hai). This interpretation shows that seafloor spreading was asymmetric and confirms that it included at least one ridge jump. Discontinuities in the seafloor fabric, characterized by large differences in basement depth and roughness, appear to be related to variations in spreading rate. Between anomalies 11 and 7 (32 to 27 Ma), spreading at an intermediate, average full rate of ≈50 mm/yr created relatively smooth basement, now thickly blanketed by sediments. The ridge then jumped to the south and created rough basement, now much shallower and covered with thinner sediments than in the north. This episode lasted from anomaly 6b to anomaly 5c (27 to ≈16 Ma) and the average spreading rate was slower, ≈35 mm/yr. After 27 Ma, spreading appears to have developed first in the eastern part of the basin and to have propagated towards the southwest in two major steps, at the time of anomalies 6b‐7, and at the time of anomaly 6. Each step correlates with a variation of the ridge orientation, from nearly E‐W to NE‐SW, and with a variation in the spreading rate. Spreading appears to have stopped synchronously along the ridge, at about 15.5 Ma. From computed fits of magnetic isochrons, we calculate 10 poles of finite rotation between the times of magnetic anomalies 11 and 5c. The poles permit reconstruction of the Oligo‐Miocene movements of Southeast Asian blocks north and south of the South China Sea. Using such reconstructions, we test quantitatively a simple scenario for the opening of the sea in which seafloor spreading results from the extrusion of Indochina relative to South China, in response to the penetration of India into Asia. This alone yields between 500 and 600 km of left‐lateral motion on the Red River‐Ailao Shan shear zone, with crustal shortening in the San Jiang region and crustal extension in Tonkin. The offset derived from the fit of magnetic isochrons on the South China Sea floor is compatible with the offset of geological markers north and south of the Red River Zone. The first phases of extension of the continental margins of the basin are probably related to motion on the Wang Chao and Three Pagodas Faults, in addition to the Red River Fault. That Indochina rotated at least 12° relative to South China implies that large‐scale “domino” models are inadequate to describe the Cenozoic tectonics of Southeast Asia. The cessation of spreading after 16 Ma appears to be roughly synchronous with the final increments of left‐lateral shear and normal uplift in the Ailao Shan (18 Ma), as well as with incipient collisions between the Australian and the Eurasian plates. Hence no other causes than the activation of new fault zones within the India‐Asia collision zone, north and east of the Red River Fault, and perhaps increased resistance to extrusion along the SE edge of Sundaland, appear to be required to terminate seafloor spreading in the largest marginal basin of the western Pacific and to change the sense of motion on the largest strike‐slip fault of SE Asia.",
    url = "https://doi.org/10.1029/92jb02280",
    doi = "10.1029/92jb02280",
    openalex = "W2048996866",
    references = "doi10102992jb01963, doi101029gm027p0023, doi101029jb093ib12p15085, doi101130001676061985961407cg20co2, doi10113000917613198210611petian20co2, doi101144gslsp19860190107, openalexw617865741"
}

The Main Central Thrust (MCT) is an important intracontinental subduction zone that accommodated a significant proportion of shortening between India and Asia during Tertiary Himalayan orogenesis. Argon 40/argon 39 geochronology indicates at least two distinct periods of thrust movement on the MCT in the Langtang National Park region of central Nepal. Ductile deformation and associated mylonitization characterizing the earlier event are constrained by 40 Ar/ 39 Ar dating of muscovites to have occurred sometime before 5.8 Ma. A later period of brittle deformation, resulting in the juxtaposition of rocks of different lithology within the MCT zone, occurred at approximately 2.3 Ma, based on 40 Ar/ 39 Ar dating of neoblastic muscovites from the brittle fault zones. The hanging wall of the MCT contains amphibolite to upper amphibolite grade gneisses and small leucogranite bodies assigned to the Greater Himalayan sequence. Argon 40/argon 39 cooling ages of muscovite and biotite from the gneisses range from 4.6 to 9.7 Ma. These dates contrast with previously obtained 16–21 Ma U‐Pb monazite and zircon ages for metasedimentary rocks from the same structural levels [Parrish et al., 1992], indicating relatively slow cooling over the early to middle Miocene interval for much of the MCT hanging wall. However, one 19.3 Ma biotite 40 Ar/ 39 Ar cooling age for a sample from the uppermost portion of the hanging wall is only slightly younger than U‐Pb monazite ages for nearby anatexites, possibly suggesting rapid cooling of the uppermost Greater Himalayan sequence by tectonic denudation associated with the structurally higher South Tibetan detachment system. The general consistency of 40 Ar/ 39 Ar ages throughout the 11‐km‐thick Greater Himalayan sequence suggests rapid cooling in late Miocene time, probably due to an increase in erosion rate related to ramping on the structurally lower Main Boundary Thrust. An alternative possibility would be massive hydrothermal resetting in late Miocene time of the entire sequence.

@article{doi10102993tc00916,
    author = "Macfarlane, Allison",
    title = "Chronology of tectonic events in the crystalline core of the Himalaya, langtang National Park, central Nepal",
    year = "1993",
    journal = "Tectonics",
    abstract = "The Main Central Thrust (MCT) is an important intracontinental subduction zone that accommodated a significant proportion of shortening between India and Asia during Tertiary Himalayan orogenesis. Argon 40/argon 39 geochronology indicates at least two distinct periods of thrust movement on the MCT in the Langtang National Park region of central Nepal. Ductile deformation and associated mylonitization characterizing the earlier event are constrained by 40 Ar/ 39 Ar dating of muscovites to have occurred sometime before 5.8 Ma. A later period of brittle deformation, resulting in the juxtaposition of rocks of different lithology within the MCT zone, occurred at approximately 2.3 Ma, based on 40 Ar/ 39 Ar dating of neoblastic muscovites from the brittle fault zones. The hanging wall of the MCT contains amphibolite to upper amphibolite grade gneisses and small leucogranite bodies assigned to the Greater Himalayan sequence. Argon 40/argon 39 cooling ages of muscovite and biotite from the gneisses range from 4.6 to 9.7 Ma. These dates contrast with previously obtained 16–21 Ma U‐Pb monazite and zircon ages for metasedimentary rocks from the same structural levels [Parrish et al., 1992], indicating relatively slow cooling over the early to middle Miocene interval for much of the MCT hanging wall. However, one 19.3 Ma biotite 40 Ar/ 39 Ar cooling age for a sample from the uppermost portion of the hanging wall is only slightly younger than U‐Pb monazite ages for nearby anatexites, possibly suggesting rapid cooling of the uppermost Greater Himalayan sequence by tectonic denudation associated with the structurally higher South Tibetan detachment system. The general consistency of 40 Ar/ 39 Ar ages throughout the 11‐km‐thick Greater Himalayan sequence suggests rapid cooling in late Miocene time, probably due to an increase in erosion rate related to ramping on the structurally lower Main Boundary Thrust. An alternative possibility would be massive hydrothermal resetting in late Miocene time of the entire sequence.",
    url = "https://doi.org/10.1029/93tc00916",
    doi = "10.1029/93tc00916",
    openalex = "W2072778478"
}

The Kumaon‐Garhwal region of the Himalaya lies near the center of the Himalayan fold‐and‐thrust belt. We have drawn two balanced cross sections, 100 km apart, through the Outer and Lesser Himalaya. The cross sections incorporate all the surface, well log, and earthquake seismic data currently available from the region. Two branch line maps showing trailing and leading branch lines and cutoff lines of the major thrusts in the region are also drawn. The three dimensional deep structure of the Outer and Lesser Himalaya is interpreted based on the balanced cross sections and the branch line maps. Deep structure of the Higher and Tethyan Himalaya is extrapolated based on surface geology and is subject to revision as more surface and seismic data become available from these areas. A sequential evolutionary model for the Kumaon Himalaya along the eastern (Pindari) section is proposed. According to this model, the Kumaon Himalaya evolved by an overall forelandward progression of thrusting, with some reactivation along the Munsiari thrust (MT), the Main Boundary thrust (MBT), and the Main Central thrust (MCT). We use structural, stratigraphic, and radiometric criteria to place time constraints on the motion of these thrusts. Earliest motion along the MBT may have occurred in Early‐Middle Paleocene, but the main episode probably started in Late Eocene and may still be continuing. Emplacement of the MT had occurred by Middle‐Late Eocene, whereas the MCT shows activity around 20 Ma, thus exhibiting break back thrusting with respect to the MT. Shortening estimates are obtained from the Pindari section. Minimum shortening in the sedimentary thrust sheets of the Outer and Lesser Himalaya is 161 km or 65%. As a first approximation, we have also restored the crystalline sheets in order to obtain shortening estimates for the entire Himalaya. Minimum shortening for the Himalaya after restoring the MCT sheet varies from 354 (76%) to 421 km (79%). These estimates were further combined with published data from the area between the MCT sheet and the Indus‐Tsangpo Suture Zone (ITSZ). Minimum shortening between the Indo‐Ganga foreland and the ITSZ thus obtained lies in the range 687–754 km or 69–72%. We compare our shortening estimates with those available from the Pakistan and Nepal Himalaya.

@article{doi10102993tc01130,
    author = "Srivastava, Praveen and Mitra, Gautam",
    title = "Thrust geometries and deep structure of the outer and lesser Himalaya, Kumaon and Garhwal (India): Implications for evolution of the Himalayan fold‐and‐thrust belt",
    year = "1994",
    journal = "Tectonics",
    abstract = "The Kumaon‐Garhwal region of the Himalaya lies near the center of the Himalayan fold‐and‐thrust belt. We have drawn two balanced cross sections, 100 km apart, through the Outer and Lesser Himalaya. The cross sections incorporate all the surface, well log, and earthquake seismic data currently available from the region. Two branch line maps showing trailing and leading branch lines and cutoff lines of the major thrusts in the region are also drawn. The three dimensional deep structure of the Outer and Lesser Himalaya is interpreted based on the balanced cross sections and the branch line maps. Deep structure of the Higher and Tethyan Himalaya is extrapolated based on surface geology and is subject to revision as more surface and seismic data become available from these areas. A sequential evolutionary model for the Kumaon Himalaya along the eastern (Pindari) section is proposed. According to this model, the Kumaon Himalaya evolved by an overall forelandward progression of thrusting, with some reactivation along the Munsiari thrust (MT), the Main Boundary thrust (MBT), and the Main Central thrust (MCT). We use structural, stratigraphic, and radiometric criteria to place time constraints on the motion of these thrusts. Earliest motion along the MBT may have occurred in Early‐Middle Paleocene, but the main episode probably started in Late Eocene and may still be continuing. Emplacement of the MT had occurred by Middle‐Late Eocene, whereas the MCT shows activity around 20 Ma, thus exhibiting break back thrusting with respect to the MT. Shortening estimates are obtained from the Pindari section. Minimum shortening in the sedimentary thrust sheets of the Outer and Lesser Himalaya is 161 km or 65\%. As a first approximation, we have also restored the crystalline sheets in order to obtain shortening estimates for the entire Himalaya. Minimum shortening for the Himalaya after restoring the MCT sheet varies from 354 (76\%) to 421 km (79\%). These estimates were further combined with published data from the area between the MCT sheet and the Indus‐Tsangpo Suture Zone (ITSZ). Minimum shortening between the Indo‐Ganga foreland and the ITSZ thus obtained lies in the range 687–754 km or 69–72\%. We compare our shortening estimates with those available from the Pakistan and Nepal Himalaya.",
    url = "https://doi.org/10.1029/93tc01130",
    doi = "10.1029/93tc01130",
    openalex = "W2082300569"
}

Field and radiometric data are used to describe and date strain and stress states in southern (longitude 88° to 91°E, latitude 28° to 30°N) and western Tibet (longitude 79° to 82°E, latitude 30° to 34°N). We factorize deformation into syncollisional and postcollisional, and we present stretching lineation and displacement orientation maps, two sections across the Indian shelf sequence, and stress orientations calculated from mesoscale fault slip data. In southern Tibet, syncollisional stretching and displacement directions trend 9°±46° and displacement is top to south. Synkinematic, low‐grade metamorphism is dated at 50 Ma at one locality in the Indian shelf sequence underlying the main mantle thrust of the Indus‐Yarlung suture. This implies Paleocene onset of continental collision for the investigated section. Postcollisional structures comprise a “backthrust” group, which includes foreland‐ and hinterland‐directed thrusts, reverse and strike‐slip faults, and folds. It dominates postcollisional deformation, is concentrated along the Indus‐Yarlung suture, and portrays N‐S compression (σ 1 trend of 8°±17°, σ 2 of 97°±17°). A “strike‐slip” group consists of conjugate strike‐slip faults, is concentrated in east trending, narrow, highly deformed zones, and indicates that N‐S compression is locally compensated by E‐W extension (σ 1 of 15°±29°, σ 3 of 103°±30°). Synkinematic muscovite dates postcollisional deformation as late early Miocene (17.5 Ma) at one locality at the suture. Strike‐slip and oblique normal (σ 3 of 60°±23°, σ 1 of 144°±21°) and normal (σ 3:114°±16°) faulting, dated between late Miocene and Recent and including active deformation, represents (dominant) E‐W and minor N‐S extension due to E‐W stretching of southern Tibet and oroclinal bending along the Himalayan arc. Restoring syncollisional and postcollisional deformation yields a minimum of 67% (258 km) shortening across the Indian shelf sequence. Incorporating recently published contraction estimates across the eastern Himalaya yields minimum shortening between undeformed India and the Indus‐Yarlung suture of 66% (536 km). The Himalaya‐Tibet orogenic system south of the Indus‐Yarlung suture had an initial width of ≥811 km in the southern Tibetan section. In western Tibet, imbrication of an ophiolite sequence of the Bangong‐Nujiang suture is top to south (stretching lineation trend of 15°±18°), and σ 3 of active deformation trends ESE. Faulting along the Shiquanhe fault zone, which transfers displacement from the northern part of the Karakorum fault to a system of rifts in western central Tibet, indicates dextral strike‐slip alternating with sinistral‐oblique normal faulting and block rotations around vertical axes during a prolonged shearing history. The Indian Shelf sequence south of Mount Kailas shows top to south imbrication (stretching lineation trend of 52°±60°). Both Indian shelf rocks and (?Oligocene‐Miocene) Kailas conglomerates record backthrusting and backfolding (σ 1 of 33°) and Recent E‐W extension (σ 3 of 85°±28°).

@article{doi10102994jb00932,
    author = "Ratschbacher, Lothar and Frisch, Wolfgang and Liu, Guanghua and Chen, Chengsheng",
    title = "Distributed deformation in southern and western Tibet during and after the India‐Asia collision",
    year = "1994",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "Field and radiometric data are used to describe and date strain and stress states in southern (longitude 88° to 91°E, latitude 28° to 30°N) and western Tibet (longitude 79° to 82°E, latitude 30° to 34°N). We factorize deformation into syncollisional and postcollisional, and we present stretching lineation and displacement orientation maps, two sections across the Indian shelf sequence, and stress orientations calculated from mesoscale fault slip data. In southern Tibet, syncollisional stretching and displacement directions trend 9°±46° and displacement is top to south. Synkinematic, low‐grade metamorphism is dated at 50 Ma at one locality in the Indian shelf sequence underlying the main mantle thrust of the Indus‐Yarlung suture. This implies Paleocene onset of continental collision for the investigated section. Postcollisional structures comprise a “backthrust” group, which includes foreland‐ and hinterland‐directed thrusts, reverse and strike‐slip faults, and folds. It dominates postcollisional deformation, is concentrated along the Indus‐Yarlung suture, and portrays N‐S compression (σ 1 trend of 8°±17°, σ 2 of 97°±17°). A “strike‐slip” group consists of conjugate strike‐slip faults, is concentrated in east trending, narrow, highly deformed zones, and indicates that N‐S compression is locally compensated by E‐W extension (σ 1 of 15°±29°, σ 3 of 103°±30°). Synkinematic muscovite dates postcollisional deformation as late early Miocene (17.5 Ma) at one locality at the suture. Strike‐slip and oblique normal (σ 3 of 60°±23°, σ 1 of 144°±21°) and normal (σ 3:114°±16°) faulting, dated between late Miocene and Recent and including active deformation, represents (dominant) E‐W and minor N‐S extension due to E‐W stretching of southern Tibet and oroclinal bending along the Himalayan arc. Restoring syncollisional and postcollisional deformation yields a minimum of 67\% (258 km) shortening across the Indian shelf sequence. Incorporating recently published contraction estimates across the eastern Himalaya yields minimum shortening between undeformed India and the Indus‐Yarlung suture of 66\% (536 km). The Himalaya‐Tibet orogenic system south of the Indus‐Yarlung suture had an initial width of ≥811 km in the southern Tibetan section. In western Tibet, imbrication of an ophiolite sequence of the Bangong‐Nujiang suture is top to south (stretching lineation trend of 15°±18°), and σ 3 of active deformation trends ESE. Faulting along the Shiquanhe fault zone, which transfers displacement from the northern part of the Karakorum fault to a system of rifts in western central Tibet, indicates dextral strike‐slip alternating with sinistral‐oblique normal faulting and block rotations around vertical axes during a prolonged shearing history. The Indian Shelf sequence south of Mount Kailas shows top to south imbrication (stretching lineation trend of 52°±60°). Both Indian shelf rocks and (?Oligocene‐Miocene) Kailas conglomerates record backthrusting and backfolding (σ 1 of 33°) and Recent E‐W extension (σ 3 of 85°±28°).",
    url = "https://doi.org/10.1029/94jb00932",
    doi = "10.1029/94jb00932",
    openalex = "W2137645231",
    references = "openalexw614437925"
}

The metamorphic core of the Himalayan orogen, or Greater Himalayan sequence, is a northward tapering prism bound at the bottom by a N dipping family of thrust faults (the Main Central thrust system) and at the top by a N dipping family of normal faults (the South Tibetan detachment system). Research in the central Annapurna Range of Nepal demonstrates a close temporal and spatial association between contractional and extensional deformation on these bounding fault systems and within the metamorphic core throughout much of the Early Miocene. The Main Central thrust system is represented here by a 2‐ to 3‐km‐thick zone of high strain that developed during two or more episodes of movement. Most of its displacement was concentrated along the Chomrong thrust, a sharp, late‐metamorphic discontinuity that places middle amphibolite facies rocks of the Greater Himalayan sequence on top of lower amphibolite facies rocks of the Lesser Himalayan sequence. The earliest demonstrable movement on this thrust system occurred ∼22.5 Ma; the most recent movement may be as young as Pliocene. The oldest element of the South Tibetan detachment system in this area is the Deorali detachment, which appears to have been active at the same time as the earliest shortening structures of the Main Central thrust system. Fabrics related to the Deorali detachment are disrupted by a previously unrecognized, SW vergent, thrust structure, the Modi Khola shear zone. The effect of this structure, which is constrained to be between 22.5 and 18.5 Ma, was to shorten rock packages that had been extended previously during movement on the Deorali detachment. Transition back to a local extensional regime after 18.5 Ma was marked by development of the Machhupuchhare detachment and related splays. Geologic evidence for rapid, two‐way transitions between contraction and extension in the Annapurna Range indicates that extensional deformation in convergent settings does not only represent gravitational collapse at the end of an orogenic cycle; it also appears to be an important factor in mountain range development.

@article{doi10102996tc01791,
    author = "Hodges, K. V. and Parrish, Randall R. and Searle, M. P.",
    title = "Tectonic evolution of the central Annapurna Range, Nepalese Himalayas",
    year = "1996",
    journal = "Tectonics",
    abstract = "The metamorphic core of the Himalayan orogen, or Greater Himalayan sequence, is a northward tapering prism bound at the bottom by a N dipping family of thrust faults (the Main Central thrust system) and at the top by a N dipping family of normal faults (the South Tibetan detachment system). Research in the central Annapurna Range of Nepal demonstrates a close temporal and spatial association between contractional and extensional deformation on these bounding fault systems and within the metamorphic core throughout much of the Early Miocene. The Main Central thrust system is represented here by a 2‐ to 3‐km‐thick zone of high strain that developed during two or more episodes of movement. Most of its displacement was concentrated along the Chomrong thrust, a sharp, late‐metamorphic discontinuity that places middle amphibolite facies rocks of the Greater Himalayan sequence on top of lower amphibolite facies rocks of the Lesser Himalayan sequence. The earliest demonstrable movement on this thrust system occurred ∼22.5 Ma; the most recent movement may be as young as Pliocene. The oldest element of the South Tibetan detachment system in this area is the Deorali detachment, which appears to have been active at the same time as the earliest shortening structures of the Main Central thrust system. Fabrics related to the Deorali detachment are disrupted by a previously unrecognized, SW vergent, thrust structure, the Modi Khola shear zone. The effect of this structure, which is constrained to be between 22.5 and 18.5 Ma, was to shorten rock packages that had been extended previously during movement on the Deorali detachment. Transition back to a local extensional regime after 18.5 Ma was marked by development of the Machhupuchhare detachment and related splays. Geologic evidence for rapid, two‐way transitions between contraction and extension in the Annapurna Range indicates that extensional deformation in convergent settings does not only represent gravitational collapse at the end of an orogenic cycle; it also appears to be an important factor in mountain range development.",
    url = "https://doi.org/10.1029/96tc01791",
    doi = "10.1029/96tc01791",
    openalex = "W2051474772"
}

The Wang Chao and Three Pagodas fault zones cut the western part of the Indochina block and run parallel to the Red River Fault. Evidence of intense ductile left‐lateral shear is found in the Lansang gneisses, which form a 5 km wide elongated core along the Wang Chao fault zone. Dating by 40 Ar/ 39 Ar shows that such deformation probably terminated around 30.5 Ma. The Wang Chao and Three Pagodas faults offset the north striking lower Mesozoic metamorphic and magmatic belt of northern Thailand. 40 Ar/ 39 Ar results suggest that this belt suffered rapid cooling in the Tertiary, probably around 23 Ma. These results imply that the extrusion of the southwestern part of Indochina occurred in the upper Eocene‐lower Oligocene. It probably induced rifting in some basins of the Gulf of Thailand and in the Malay and Mekong basins. In the Oligo‐Miocene, the continuing penetration of India into Asia culminated with the extrusion of all of Indochina along the Ailao Shan‐Red River fault. This occurred concurrently with the onset of E‐W extension more to the south. Plotting in a geographical reference frame the diachronic time spans of movement on left‐lateral faults east and southeast of Tibet implies that the northward movement of the Indian indenter successively initiated new strike‐slip faults located farther and farther north along its path.

@article{doi10102996jb03831,
    author = "Lacassin, Robin and Maluski, Henri and Leloup, Philippe Hervé and Tapponnier, Paul and Hinthong, Chaiyan and Siribhakdi, Kanchit and Chuaviroj, Saengathit and Charoenravat, Adul",
    title = "Tertiary diachronic extrusion and deformation of western Indochina: Structural and 40 Ar/ 39 Ar evidence from NW Thailand",
    year = "1997",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "The Wang Chao and Three Pagodas fault zones cut the western part of the Indochina block and run parallel to the Red River Fault. Evidence of intense ductile left‐lateral shear is found in the Lansang gneisses, which form a 5 km wide elongated core along the Wang Chao fault zone. Dating by 40 Ar/ 39 Ar shows that such deformation probably terminated around 30.5 Ma. The Wang Chao and Three Pagodas faults offset the north striking lower Mesozoic metamorphic and magmatic belt of northern Thailand. 40 Ar/ 39 Ar results suggest that this belt suffered rapid cooling in the Tertiary, probably around 23 Ma. These results imply that the extrusion of the southwestern part of Indochina occurred in the upper Eocene‐lower Oligocene. It probably induced rifting in some basins of the Gulf of Thailand and in the Malay and Mekong basins. In the Oligo‐Miocene, the continuing penetration of India into Asia culminated with the extrusion of all of Indochina along the Ailao Shan‐Red River fault. This occurred concurrently with the onset of E‐W extension more to the south. Plotting in a geographical reference frame the diachronic time spans of movement on left‐lateral faults east and southeast of Tibet implies that the northward movement of the Indian indenter successively initiated new strike‐slip faults located farther and farther north along its path.",
    url = "https://doi.org/10.1029/96jb03831",
    doi = "10.1029/96jb03831",
    openalex = "W1980209354",
    references = "doi1010160191814180900413"
}

@article{doi101016s0743954798000269,
    author = "Weidinger, Johannes T.",
    title = "Case history and hazard analysis of two lake-damming landslides in the Himalayas",
    year = "1998",
    journal = "Journal of Asian Earth Sciences",
    url = "https://doi.org/10.1016/s0743-9547(98)00026-9",
    doi = "10.1016/s0743-9547(98)00026-9",
    openalex = "W1975181032",
    references = "doi1010079783709157923, doi101007bf01823808, doi101016004019517690069x, doi1010160040195196000789, doi1011300016760619881001054tfafon23co2, doi1023071794401, doi103126jngsv18i032267, openalexw1579200383, openalexw2182411511, openalexw614437925"
}

Sedimentologic, petrographic, and U‐Pb detrital zircon ages from middle Eocene through early Miocene sedimentary rocks in the Lesser Himalayan zone of western and central Nepal indicate that a peripheral foreland basin system had developed in the eastern Himalayan collision zone by middle Eocene time. The shallow‐marine, Eocene Bhainskati Formation accumulated in a back‐bulge depozone between a southward migrating forebulge and the Indian craton. Migration of the forebulge through this region during Eocene‐Oligocene time produced a regional unconformity that spans ∼15–20 Myr. By early Miocene time, the forebulge unconformity was onlapped by the distal fringes of the southward migrating foredeep depozone, represented by fluvial deposits of the Dumri Formation. Continued southward migration of the foredeep during the Neogene accommodated the fluvial Siwalik Group. Light mineral provenance data and U‐Pb detrital zircon ages suggest that the Bhainskati was derived partly from Tethyan sedimentary rocks of the Tibetan Himalayan zone during initial growth of the Himalayan fold‐thrust belt. The Dumri was derived from metasedimentary and crystalline rocks of the Greater Himalayan zone during emplacement of the Main Central thrust and contemporaneous tectonic unroofing by normal faulting along the South Tibetan detachment system. The Lesser Himalayan crystalline thrust sheets were emplaced soon after deposition of the Dumri Formation, ∼15–10 Ma. Paleocurrent and lithofacies data from the Dumri Formation indicate deposition by west‐southwestward flowing rivers that drained into the Indus portion of the Himalayan foreland basin system during the early Miocene. Thick channel sandstones in the lower Dumri may represent the early Miocene counterpart of the modern Ganges River. Eastward diversion of the Ganges drainage system to near its present location had occurred by ∼15 Ma, as the high‐standing Aravalli Range on the northern Indian shield approached the front of the fold‐thrust belt. Assuming reasonable values for the flexural rigidity of Indian lithosphere, the time span of the forebulge unconformity yields a velocity of ∼14–33 mm/yr for the southward migration of the fold‐thrust belt relative to India. This range of values is consistent with Neogene and present‐day estimates and suggests that only one third to one half of India‐Eurasia convergence has been accommodated by shortening in the Himalayan fold‐thrust belt since the onset of collision.

@article{doi10102998tc02598,
    author = "DeCelles, Peter G. and Gehrels, George E. and Quade, Jay and Ojha, T. P.",
    title = "Eocene‐early Miocene foreland basin development and the history of Himalayan thrusting, western and central Nepal",
    year = "1998",
    journal = "Tectonics",
    abstract = "Sedimentologic, petrographic, and U‐Pb detrital zircon ages from middle Eocene through early Miocene sedimentary rocks in the Lesser Himalayan zone of western and central Nepal indicate that a peripheral foreland basin system had developed in the eastern Himalayan collision zone by middle Eocene time. The shallow‐marine, Eocene Bhainskati Formation accumulated in a back‐bulge depozone between a southward migrating forebulge and the Indian craton. Migration of the forebulge through this region during Eocene‐Oligocene time produced a regional unconformity that spans ∼15–20 Myr. By early Miocene time, the forebulge unconformity was onlapped by the distal fringes of the southward migrating foredeep depozone, represented by fluvial deposits of the Dumri Formation. Continued southward migration of the foredeep during the Neogene accommodated the fluvial Siwalik Group. Light mineral provenance data and U‐Pb detrital zircon ages suggest that the Bhainskati was derived partly from Tethyan sedimentary rocks of the Tibetan Himalayan zone during initial growth of the Himalayan fold‐thrust belt. The Dumri was derived from metasedimentary and crystalline rocks of the Greater Himalayan zone during emplacement of the Main Central thrust and contemporaneous tectonic unroofing by normal faulting along the South Tibetan detachment system. The Lesser Himalayan crystalline thrust sheets were emplaced soon after deposition of the Dumri Formation, ∼15–10 Ma. Paleocurrent and lithofacies data from the Dumri Formation indicate deposition by west‐southwestward flowing rivers that drained into the Indus portion of the Himalayan foreland basin system during the early Miocene. Thick channel sandstones in the lower Dumri may represent the early Miocene counterpart of the modern Ganges River. Eastward diversion of the Ganges drainage system to near its present location had occurred by ∼15 Ma, as the high‐standing Aravalli Range on the northern Indian shield approached the front of the fold‐thrust belt. Assuming reasonable values for the flexural rigidity of Indian lithosphere, the time span of the forebulge unconformity yields a velocity of ∼14–33 mm/yr for the southward migration of the fold‐thrust belt relative to India. This range of values is consistent with Neogene and present‐day estimates and suggests that only one third to one half of India‐Eurasia convergence has been accommodated by shortening in the Himalayan fold‐thrust belt since the onset of collision.",
    url = "https://doi.org/10.1029/98tc02598",
    doi = "10.1029/98tc02598",
    openalex = "W2095134742",
    references = "doi101029tc008i004p00881, doi101111j136521171992tb00050x, doi101111j136530911989tb00817x"
}

@article{doi101016s1367912099000474,
    author = "Upreti, Bishal Nath",
    title = "An overview of the stratigraphy and tectonics of the Nepal Himalaya",
    year = "1999",
    journal = "Journal of Asian Earth Sciences",
    url = "https://doi.org/10.1016/s1367-9120(99)00047-4",
    doi = "10.1016/s1367-9120(99)00047-4",
    openalex = "W2040484660",
    references = "crossref1989tectonics, doi1010079783709157923, doi101007bf01823808, doi1010160040195187902484, doi1010160191814181900328, doi10102993tc01130, doi10102994gl02971, doi101038386061a0, doi1011300016760619981100002nfbdeu23co2, doi101130spe269, doi101144gsjgs13710001, doi1023071794401, openalexw2182411511, openalexw614437925"
}

We analyze geomorphic evidence of recent crustal deformation in the sub‐Himalaya of central Nepal, south of the Kathmandu Basin. The Main Frontal Thrust fault (MFT), which marks the southern edge of the sub‐Himalayan fold belt, is the only active structure in that area. Active fault bend folding at the MFT is quantified from structural geology and fluvial terraces along the Bagmati and Bakeya Rivers. Two major and two minor strath terraces are recognized and dated to be 9.2, 2.2, and 6.2, 3.7 calibrated (cal) kyr old, respectively. Rock uplift of up to 1.5 cm/yr is derived from river incision, accounting for sedimentation in the Gangetic plain and channel geometry changes. Rock uplift profiles are found to correlate with bedding dip angles, as expected in fault bend folding. It implies that thrusting along the MFT has absorbed 21±1.5 mm/yr of N‐S shortening on average over the Holocene period. The ±1.5 mm/yr defines the 68% confidence interval and accounts for uncertainties in age, elevation measurements, initial geometry of the deformed terraces, and seismic cycle. At the longitude of Kathmandu, localized thrusting along the Main Frontal Thrust fault must absorb most of the shortening across the Himalaya. By contrast, microseismicity and geodetic monitoring over the last decade suggest that interseismic strain is accumulating beneath the High Himalaya, 50–100 km north of the active fold zone, where the Main Himalayan Thrust (MHT) fault roots into a ductile décollement beneath southern Tibet. In the interseismic period the MHT is locked, and elastic deformation accumulates until being released by large (M w > 8) earthquakes. These earthquakes break the MHT up to the near surface at the front of the Himalayan foothills and result in incremental activation of the MFT.

@article{doi1010291999jb900292,
    author = "Lavé, Jérôme and Avouac, Jean‐Philippe",
    title = "Active folding of fluvial terraces across the Siwaliks Hills, Himalayas of central Nepal",
    year = "2000",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "We analyze geomorphic evidence of recent crustal deformation in the sub‐Himalaya of central Nepal, south of the Kathmandu Basin. The Main Frontal Thrust fault (MFT), which marks the southern edge of the sub‐Himalayan fold belt, is the only active structure in that area. Active fault bend folding at the MFT is quantified from structural geology and fluvial terraces along the Bagmati and Bakeya Rivers. Two major and two minor strath terraces are recognized and dated to be 9.2, 2.2, and 6.2, 3.7 calibrated (cal) kyr old, respectively. Rock uplift of up to 1.5 cm/yr is derived from river incision, accounting for sedimentation in the Gangetic plain and channel geometry changes. Rock uplift profiles are found to correlate with bedding dip angles, as expected in fault bend folding. It implies that thrusting along the MFT has absorbed 21±1.5 mm/yr of N‐S shortening on average over the Holocene period. The ±1.5 mm/yr defines the 68\% confidence interval and accounts for uncertainties in age, elevation measurements, initial geometry of the deformed terraces, and seismic cycle. At the longitude of Kathmandu, localized thrusting along the Main Frontal Thrust fault must absorb most of the shortening across the Himalaya. By contrast, microseismicity and geodetic monitoring over the last decade suggest that interseismic strain is accumulating beneath the High Himalaya, 50–100 km north of the active fold zone, where the Main Himalayan Thrust (MHT) fault roots into a ductile décollement beneath southern Tibet. In the interseismic period the MHT is locked, and elastic deformation accumulates until being released by large (M w > 8) earthquakes. These earthquakes break the MHT up to the near surface at the front of the Himalayan foothills and result in incremental activation of the MFT.",
    url = "https://doi.org/10.1029/1999jb900292",
    doi = "10.1029/1999jb900292",
    openalex = "W2047661207",
    references = "doi101038379505a0, doi101038386061a0, doi1023071794401, doi102475ajs27511"
}

The largest tract of ultrahigh‐pressure rocks, the Dabie‐Hong'an area of China, was exhumed from 125 km depth by a combination of normal‐sense shear from beneath the hanging wall Sino‐Korean craton, southeastward thrusting onto the footwall Yangtze craton, and orogen‐parallel eastward extrusion. Prior to exhumation the UHP slab extended into the mantle a downdip distance of 125–200 km at its eastern end, whereas it was subducted perhaps only 20–30 km at its far western end ∼200 km away. Structural reconstructions imply that the slab was >10 km thick. U/Pb zircon and 40 Ar/ 39 Ar geochronology indicate that exhumation up to crustal depths occurred diachronously between 240 and ∼225–210 Ma, reflecting a vertical exhumation rate of >2 mm/yr. The upper boundary of the slab is the Huwan shear zone, a normal‐sense detachment that reactivated the plate suture. The lower boundary is represented by the Lower Yangtze fold‐thrust belt. NW‐trending stretching lineations, NE‐vergent, WNW‐ESE trending folds, dominant top‐NW shear, and conjugate, but overall asymmetric, shear band fabrics, document that exhumation was accomplished by updip and orogen‐parallel extrusion accompanied by layer‐parallel thinning. The orientation and shape of the folds, and a change from SE to SW flow directions, imply that the slab rotated clockwise about a western pivot during exhumation; this rotation was likely caused by the eastward increasing depth of subduction mentioned above, combined with a possible marginal basin and a weak eastern plate boundary. Exhumation of the slab produced considerable shortening in the Lower Yangtze fold‐thrust belt, perhaps producing the foreland orocline.

@article{doi1010292000jb900039,
    author = "Hacker, Bradley R. and Ratschbacher, Lothar and Webb, Laura E. and McWilliams, Michael and Ireland, T. R. and Calvert, Andrew T. and Dong, Shuwen and Wenk, Hans‐Rudolf and Chateigner, Daniel",
    title = "Exhumation of ultrahigh‐pressure continental crust in east central China: Late Triassic‐Early Jurassic tectonic unroofing",
    year = "2000",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "The largest tract of ultrahigh‐pressure rocks, the Dabie‐Hong'an area of China, was exhumed from 125 km depth by a combination of normal‐sense shear from beneath the hanging wall Sino‐Korean craton, southeastward thrusting onto the footwall Yangtze craton, and orogen‐parallel eastward extrusion. Prior to exhumation the UHP slab extended into the mantle a downdip distance of 125–200 km at its eastern end, whereas it was subducted perhaps only 20–30 km at its far western end ∼200 km away. Structural reconstructions imply that the slab was >10 km thick. U/Pb zircon and 40 Ar/ 39 Ar geochronology indicate that exhumation up to crustal depths occurred diachronously between 240 and ∼225–210 Ma, reflecting a vertical exhumation rate of >2 mm/yr. The upper boundary of the slab is the Huwan shear zone, a normal‐sense detachment that reactivated the plate suture. The lower boundary is represented by the Lower Yangtze fold‐thrust belt. NW‐trending stretching lineations, NE‐vergent, WNW‐ESE trending folds, dominant top‐NW shear, and conjugate, but overall asymmetric, shear band fabrics, document that exhumation was accomplished by updip and orogen‐parallel extrusion accompanied by layer‐parallel thinning. The orientation and shape of the folds, and a change from SE to SW flow directions, imply that the slab rotated clockwise about a western pivot during exhumation; this rotation was likely caused by the eastward increasing depth of subduction mentioned above, combined with a possible marginal basin and a weak eastern plate boundary. Exhumation of the slab produced considerable shortening in the Lower Yangtze fold‐thrust belt, perhaps producing the foreland orocline.",
    url = "https://doi.org/10.1029/2000jb900039",
    doi = "10.1029/2000jb900039",
    openalex = "W2021345743",
    references = "doi1010160191814180900413, openalexw3139812027"
}

The topographic evolution of orogens is fundamentally dictated by rates and patterns of bedrock-channel incision. Quantitative field assessments of process-based laws are needed to accurately describe landscape uplift and denudation in response to tectonics and climate. We evaluate and calibrate the shear stress (or similar unit stream-power) bedrock-incision model by studying stream profiles in a tectonically active mountain range. Previous work on emergent marine terraces in the Mendocino triple junction region of northern California provides spatial and temporal control on rock-uplift rates. Digital elevation models and field data are used to quantify differences in landscape morphology associated with along-strike northwest to southeast changes in tectonic and climatic conditions. Analysis of longitudinal profiles supports the hypothesis that the study-area channels are in equilibrium with current uplift and climatic conditions, consistent with theoretical calculations of system response time based on the shear-stress model. Within uncertainty, the profile concavity (𝛉) of the trunk streams is constant throughout the study area (𝛉 ≈ 0.43), as predicted by the model. Channel steepness correlates with uplift rate. These data help constrain the two key unknown model parameters, the coefficient of erosion (K) and the exponent associated with channel gradient (n). This analysis shows that K cannot be treated as a constant throughout the study area, despite generally homogeneous substrate properties. For a reasonable range of slope-exponent values (n), best-fit values of K are positively correlated with uplift rate. This correlation has important implications for landscape-evolution models and likely reflects dynamic adjustment of K to tectonic changes, due to variations in orographic precipitation, and perhaps channel width, sediment load, and frequency of debris flows. The apparent variation in K makes a unique value of n impossible to constrain with present data.

@article{doi1011300016760620001121250lrttfd20co2,
    author = "Snyder, Noah P. and Whipple, K. X. and Tucker, Gregory E. and Merritts, Dorothy J.",
    title = "Landscape response to tectonic forcing: Digital elevation model analysis of stream profiles in the Mendocino triple junction region, northern California",
    year = "2000",
    journal = "Geological Society of America Bulletin",
    abstract = "The topographic evolution of orogens is fundamentally dictated by rates and patterns of bedrock-channel incision. Quantitative field assessments of process-based laws are needed to accurately describe landscape uplift and denudation in response to tectonics and climate. We evaluate and calibrate the shear stress (or similar unit stream-power) bedrock-incision model by studying stream profiles in a tectonically active mountain range. Previous work on emergent marine terraces in the Mendocino triple junction region of northern California provides spatial and temporal control on rock-uplift rates. Digital elevation models and field data are used to quantify differences in landscape morphology associated with along-strike northwest to southeast changes in tectonic and climatic conditions. Analysis of longitudinal profiles supports the hypothesis that the study-area channels are in equilibrium with current uplift and climatic conditions, consistent with theoretical calculations of system response time based on the shear-stress model. Within uncertainty, the profile concavity (𝛉) of the trunk streams is constant throughout the study area (𝛉 ≈ 0.43), as predicted by the model. Channel steepness correlates with uplift rate. These data help constrain the two key unknown model parameters, the coefficient of erosion (K) and the exponent associated with channel gradient (n). This analysis shows that K cannot be treated as a constant throughout the study area, despite generally homogeneous substrate properties. For a reasonable range of slope-exponent values (n), best-fit values of K are positively correlated with uplift rate. This correlation has important implications for landscape-evolution models and likely reflects dynamic adjustment of K to tectonic changes, due to variations in orographic precipitation, and perhaps channel width, sediment load, and frequency of debris flows. The apparent variation in K makes a unique value of n impossible to constrain with present data.",
    url = "https://doi.org/10.1130/0016-7606(2000)112<1250:lrttfd>2.0.co;2",
    doi = "10.1130/0016-7606(2000)112<1250:lrttfd>2.0.co;2",
    openalex = "W2044723506",
    references = "doi10102994wr00757, doi101029gm107p0297, doi101038379505a0"
}

@article{doi101130001676062000112324tothas20co2,
    author = "Hodges, K. V.",
    title = "Tectonics of the Himalaya and southern Tibet from two perspectives",
    year = "2000",
    journal = "Geological Society of America Bulletin",
    url = "https://doi.org/10.1130/0016-7606(2000)112<324:tothas>2.0.co;2",
    doi = "10.1130/0016-7606(2000)112<324:tothas>2.0.co;2",
    openalex = "W2055356153",
    references = "brasier1987microfossils, coward1986collision, doi101007bf02440107, doi1010160012821x82900073, doi1010160012821x85901657, doi101016s0743954798000026, doi1010291999tc900042, doi10102993rg02030, doi101029gd003p0215, doi101029jb075i014p02625, doi101029jb093ib12p15085, doi101029tc008i004p00881, doi101038311615a0, doi101038373055a0, doi101038386061a0, doi101126science1894201419, doi101126science25550521663, doi101126science2765313788, doi101130001676061986971037doowat20co2, doi10113000917613198210611petian20co2, doi101130spe269, doi101130spe281p1, doi101144gslsp19860190107, doi1023071794401, doi102475ajs27511, openalexw1928320224, openalexw2010625414"
}

@article{doi101016s0040195101001299,
    author = "Kayal, J. R.",
    title = "Microearthquake activity in some parts of the Himalaya and the tectonic model",
    year = "2001",
    journal = "Tectonophysics",
    url = "https://doi.org/10.1016/s0040-1951(01)00129-9",
    doi = "10.1016/s0040-1951(01)00129-9",
    openalex = "W2007831757",
    references = "doi101016004019517690069x"
}

The Main Central Thrust (MCT) juxtaposes the high‐grade Greater Himalayan Crystallines over the lower‐grade Lesser Himalaya Formation; an apparent inverted metamorphic sequence characterizes the shear zone that underlies the thrust. Garnet‐bearing assemblages sampled along the Marysandi River and Darondi Khola in the Annapurna region of central Nepal show striking differences in garnet zoning of Mn, Ca, Mg, and Fe above and below the MCT. Thermobarometry of MCT footwall rocks yields apparent inverted temperature and pressure gradients of ∼18°C km −1 and ∼0.06 km MPa −1, respectively. Pressure‐temperature (P‐T) paths calculated for upper Lesser Himalaya samples that preserve prograde compositions show evidence of decompression during heating, whereas garnets from the structurally lower sequences grew during an increase in both pressure and temperature. In situ (i.e., analyzed in thin section) ion microprobe ages of monazites from rocks immediately beneath the Greater Himalayan Crystallines yield ages from 18 to 22 Ma, whereas late Miocene and Pliocene monazite ages characterize rocks within the apparent inverted metamorphic sequence. A Lesser Himalayan sample collected near the garnet isograd along the Marysandi River transect contains 3.3±0.1 Ma monazite ages (P ≈ 0.72 GPa, T ≈ 535°C). This remarkably young age suggests that this portion of the MCT shear zone accommodated a minimum of ∼30 km of slip over the last 3 Ma (i.e., a slip rate of >10 mm yr −1) and thus could account for nearly half of the convergence across the Himalaya in this period. The distribution of ages and P‐T histories reported here are consistent with a thermokinematic model in which the inverted metamorphic sequences underlying the MCT formed by the transposition of right‐way‐up metamorphic sequences during late Miocene‐Pliocene shearing.

@article{doi1010292000jb900375,
    author = "Catlos, Elizabeth J. and Harrison, T. Mark and Kohn, Matthew J. and Grove, Marty and Ryerson, F. J. and Manning, C. E. and Upreti, Bishal Nath",
    title = "Geochronologic and thermobarometric constraints on the evolution of the Main Central Thrust, central Nepal Himalaya",
    year = "2001",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "The Main Central Thrust (MCT) juxtaposes the high‐grade Greater Himalayan Crystallines over the lower‐grade Lesser Himalaya Formation; an apparent inverted metamorphic sequence characterizes the shear zone that underlies the thrust. Garnet‐bearing assemblages sampled along the Marysandi River and Darondi Khola in the Annapurna region of central Nepal show striking differences in garnet zoning of Mn, Ca, Mg, and Fe above and below the MCT. Thermobarometry of MCT footwall rocks yields apparent inverted temperature and pressure gradients of ∼18°C km −1 and ∼0.06 km MPa −1, respectively. Pressure‐temperature (P‐T) paths calculated for upper Lesser Himalaya samples that preserve prograde compositions show evidence of decompression during heating, whereas garnets from the structurally lower sequences grew during an increase in both pressure and temperature. In situ (i.e., analyzed in thin section) ion microprobe ages of monazites from rocks immediately beneath the Greater Himalayan Crystallines yield ages from 18 to 22 Ma, whereas late Miocene and Pliocene monazite ages characterize rocks within the apparent inverted metamorphic sequence. A Lesser Himalayan sample collected near the garnet isograd along the Marysandi River transect contains 3.3±0.1 Ma monazite ages (P ≈ 0.72 GPa, T ≈ 535°C). This remarkably young age suggests that this portion of the MCT shear zone accommodated a minimum of ∼30 km of slip over the last 3 Ma (i.e., a slip rate of >10 mm yr −1) and thus could account for nearly half of the convergence across the Himalaya in this period. The distribution of ages and P‐T histories reported here are consistent with a thermokinematic model in which the inverted metamorphic sequences underlying the MCT formed by the transposition of right‐way‐up metamorphic sequences during late Miocene‐Pliocene shearing.",
    url = "https://doi.org/10.1029/2000jb900375",
    doi = "10.1029/2000jb900375",
    openalex = "W2094360812",
    references = "doi101016s1367912099000474"
}

Regional mapping, stratigraphic study, and 40 Ar/ 39 Ar geochronology provide the basis for an incremental restoration of the Himalayan fold‐thrust belt in western Nepal. Tectonostratigraphic zonation developed in other regions of the Himalaya is applicable, with minor modifications, in western Nepal. From south to north the major structural features are (1) the Main Frontal thrust system, comprising the Main Frontal thrust and two to three thrust sheets of Neogene foreland basin deposits; (2) the Main Boundary thrust sheet, which consists of Proterozoic to early Miocene, Lesser Himalayan metasedimentary rocks; (3) the Ramgarh thrust sheet, composed of Paleoproterozoic low‐grade metasedimentary rocks; (4) the Dadeldhura thrust sheet, which consists of medium‐grade metamorphic rocks, Cambrian‐Ordovician granite and granitic mylonite, and early Paleozoic Tethyan rocks; (5) the Lesser Himalayan duplex, which is a large composite antiformal stack and hinterland dipping duplex; and (6) the Main Central thrust zone, a broad ductile shear zone. The major structures formed in a general southward progression beginning with the Main Central thrust in late early Miocene time. Eocene‐Oligocene thrusting in the Tibetan Himalaya, north of the study area, is inferred from the detrital unroofing record. On the basis of 40 Ar/ 39 Ar cooling ages and provenance data from synorogenic sediments, emplacement of the Dadeldhura thrust sheet took place in early Miocene time. The Ramgarh thrust sheet was emplaced between ∼15 and ∼10 Ma. The Lesser Himalayan duplex began to grow by ∼10 Ma, simultaneously folding the north limb of the Dadeldhura synform. The Main Boundary thrust became active in latest Miocene‐Pliocene time; transport of its hanging wall rocks over an ∼8‐km‐high footwall ramp folded the south limb of the Dadeldhura synform. Thrusts in the Subhimalayan zone became active in Pliocene time. The minimum total shortening in this portion of the Himalayan fold‐thrust belt since early Miocene time (excluding the Tibetan zone) is ∼418–493 km, the variation depending on the actual amounts of shortening accommodated by the Main Central and Dadeldhura thrusts. The rate of shortening ranges between 19 and 22 mm/yr for this period of time. When previous estimates of shortening in the Tibetan Himalaya are included, the minimum total amount of shortening in the foldthrust belt amounts to 628–667 km. This estimate neglects shortening accommodated by small‐scale structures and internal strain and is therefore likely to fall significantly below the actual amount of total shortening.

@article{doi1010292000tc001226,
    author = "DeCelles, Peter G. and Robinson, Delores M. and Quade, Jay and Ojha, T. P. and Garzione, Carmala N. and Copeland, Peter and Upreti, Bishal Nath",
    title = "Stratigraphy, structure, and tectonic evolution of the Himalayan fold‐thrust belt in western Nepal",
    year = "2001",
    journal = "Tectonics",
    abstract = "Regional mapping, stratigraphic study, and 40 Ar/ 39 Ar geochronology provide the basis for an incremental restoration of the Himalayan fold‐thrust belt in western Nepal. Tectonostratigraphic zonation developed in other regions of the Himalaya is applicable, with minor modifications, in western Nepal. From south to north the major structural features are (1) the Main Frontal thrust system, comprising the Main Frontal thrust and two to three thrust sheets of Neogene foreland basin deposits; (2) the Main Boundary thrust sheet, which consists of Proterozoic to early Miocene, Lesser Himalayan metasedimentary rocks; (3) the Ramgarh thrust sheet, composed of Paleoproterozoic low‐grade metasedimentary rocks; (4) the Dadeldhura thrust sheet, which consists of medium‐grade metamorphic rocks, Cambrian‐Ordovician granite and granitic mylonite, and early Paleozoic Tethyan rocks; (5) the Lesser Himalayan duplex, which is a large composite antiformal stack and hinterland dipping duplex; and (6) the Main Central thrust zone, a broad ductile shear zone. The major structures formed in a general southward progression beginning with the Main Central thrust in late early Miocene time. Eocene‐Oligocene thrusting in the Tibetan Himalaya, north of the study area, is inferred from the detrital unroofing record. On the basis of 40 Ar/ 39 Ar cooling ages and provenance data from synorogenic sediments, emplacement of the Dadeldhura thrust sheet took place in early Miocene time. The Ramgarh thrust sheet was emplaced between ∼15 and ∼10 Ma. The Lesser Himalayan duplex began to grow by ∼10 Ma, simultaneously folding the north limb of the Dadeldhura synform. The Main Boundary thrust became active in latest Miocene‐Pliocene time; transport of its hanging wall rocks over an ∼8‐km‐high footwall ramp folded the south limb of the Dadeldhura synform. Thrusts in the Subhimalayan zone became active in Pliocene time. The minimum total shortening in this portion of the Himalayan fold‐thrust belt since early Miocene time (excluding the Tibetan zone) is ∼418–493 km, the variation depending on the actual amounts of shortening accommodated by the Main Central and Dadeldhura thrusts. The rate of shortening ranges between 19 and 22 mm/yr for this period of time. When previous estimates of shortening in the Tibetan Himalaya are included, the minimum total amount of shortening in the foldthrust belt amounts to 628–667 km. This estimate neglects shortening accommodated by small‐scale structures and internal strain and is therefore likely to fall significantly below the actual amount of total shortening.",
    url = "https://doi.org/10.1029/2000tc001226",
    doi = "10.1029/2000tc001226",
    openalex = "W2087411929",
    references = "doi101007bf01823808, doi101016s1367912099000474, openalexw614437925"
}

The pattern of fluvial incision across the Himalayas of central Nepal is estimated from the distribution of Holocene and Pleistocene terraces and from the geometry of modern channels along major rivers draining across the range. The terraces provide good constraints on incision rates across the Himalayan frontal folds (Sub‐Himalaya or Siwaliks Hills) where rivers are forced to cut down into rising anticlines and have abandoned numerous strath terraces. Farther north and upstream, in the Lesser Himalaya, prominent fill terraces were deposited, probably during the late Pleistocene, and were subsequently incised. The amount of bedrock incision beneath the fill deposits is generally small, suggesting a slow rate of fluvial incision in the Lesser Himalaya. The terrace record is lost in the high range where the rivers are cutting steep gorges. To complement the terrace study, fluvial incision was also estimated from the modern channel geometries using an estimate of the shear stress exerted by the flowing water at the bottom of the channel as a proxy for river incision rate. This approach allows quantification of the effect of variations in channel slope, width, and discharge on the incision rate of a river; the determination of incision rates requires an additional lithological calibration. The two approaches are shown to yield consistent results when applied to the same reach or if incision profiles along nearby parallel reaches are compared. In the Sub‐Himalaya, river incision is rapid, with values up to 10–15 mm/yr. It does not exceed a few millimeters per year in the Lesser Himalaya, and rises abruptly at the front of the high range to reach values of ∼4–8 mm/yr within a 50‐km‐wide zone that coincides with the position of the highest Himalayan peaks. Sediment yield derived from the measurement of suspended load in Himalayan rivers suggests that fluvial incision drives hillslope denudation of the landscape at the scale of the whole range. The observed pattern of erosion is found to closely mimic uplift as predicted by a mechanical model taking into account erosion and slip along the flat‐ramp‐flat geometry of the Main Himalayan Thrust fault. The morphology of the range reflects a dynamic equilibrium between present‐day tectonics and surface processes. The sharp relief together with the high uplift rates in the Higher Himalaya reflects thrusting over the midcrustal ramp rather than the isostatic response to reincision of the Tibetan Plateau driven by late Cenozoic climate change, or late Miocene reactivation of the Main Central Thrust.

@article{doi1010292001jb000359,
    author = "Lavé, Jérôme and Avouac, Jean‐Philippe",
    title = "Fluvial incision and tectonic uplift across the Himalayas of central Nepal",
    year = "2001",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "The pattern of fluvial incision across the Himalayas of central Nepal is estimated from the distribution of Holocene and Pleistocene terraces and from the geometry of modern channels along major rivers draining across the range. The terraces provide good constraints on incision rates across the Himalayan frontal folds (Sub‐Himalaya or Siwaliks Hills) where rivers are forced to cut down into rising anticlines and have abandoned numerous strath terraces. Farther north and upstream, in the Lesser Himalaya, prominent fill terraces were deposited, probably during the late Pleistocene, and were subsequently incised. The amount of bedrock incision beneath the fill deposits is generally small, suggesting a slow rate of fluvial incision in the Lesser Himalaya. The terrace record is lost in the high range where the rivers are cutting steep gorges. To complement the terrace study, fluvial incision was also estimated from the modern channel geometries using an estimate of the shear stress exerted by the flowing water at the bottom of the channel as a proxy for river incision rate. This approach allows quantification of the effect of variations in channel slope, width, and discharge on the incision rate of a river; the determination of incision rates requires an additional lithological calibration. The two approaches are shown to yield consistent results when applied to the same reach or if incision profiles along nearby parallel reaches are compared. In the Sub‐Himalaya, river incision is rapid, with values up to 10–15 mm/yr. It does not exceed a few millimeters per year in the Lesser Himalaya, and rises abruptly at the front of the high range to reach values of ∼4–8 mm/yr within a 50‐km‐wide zone that coincides with the position of the highest Himalayan peaks. Sediment yield derived from the measurement of suspended load in Himalayan rivers suggests that fluvial incision drives hillslope denudation of the landscape at the scale of the whole range. The observed pattern of erosion is found to closely mimic uplift as predicted by a mechanical model taking into account erosion and slip along the flat‐ramp‐flat geometry of the Main Himalayan Thrust fault. The morphology of the range reflects a dynamic equilibrium between present‐day tectonics and surface processes. The sharp relief together with the high uplift rates in the Higher Himalaya reflects thrusting over the midcrustal ramp rather than the isostatic response to reincision of the Tibetan Plateau driven by late Cenozoic climate change, or late Miocene reactivation of the Main Central Thrust.",
    url = "https://doi.org/10.1029/2001jb000359",
    doi = "10.1029/2001jb000359",
    openalex = "W2016138287",
    references = "doi101029gm107p0297, doi101038386061a0, doi101046j1365246x199900802x, doi1023071794401"
}

In the Shiquanhe area of far‐western Tibet, mid‐Cretaceous strata lie unconformable on ophiolitic melange and Jurassic flysch associated with the Bangong‐Nujiang suture zone. On the basis of our mapping and geochronologic studies, we suggest that these Cretaceous strata were shortened by >57% over a north south distance of 50 km during Late Cretaceous‐early Tertiary time. The Late Cretaceous Narangjiapo thrust placed Permian strata >20 km over ophiolitic melange and Cretaceous strata. North of the Narangjiapo thrust, >40 km of shortening was accommodated by the Late Cretaceous‐early Tertiary south directed Jaggang thrust system that involves Jurassic flysch and Cretaceous strata, and roots into a decollement within ophiolitic melange. The most recent shortening was accommodated to the south of the Narangjiapo thrust, along the north dipping Shiquanhe thrust. The Shiquanhe thrust cuts flat‐lying 22.6 ± 0.3 Ma volcanic rocks and underlying folded, Tertiary nonmarine strata in its footwall and was likely active during slip along the Oligocene Gangdese thrust system of southern Tibet. Ophiolitic melange and structurally overlying Jurassic flysch near Shiquanhe are interpreted to represent remnants of a subduction‐accretion complex and forearc basin, respectively, that were obducted southward onto the margin of the Lhasa terrane during Late Jurassic‐Early Cretaceous closure of the Bangong‐Nujiang Ocean. Subsequent imbrication of the obducted sheet could have produced the two east‐west trending belts of ophiolitic melanges, separated by ∼100 km, in western Tibet. Late Cretaceous‐early Tertiary thin‐skinned shortening may have been accommodated in the deeper crust by northward underthrusting and duplexing of Lhasa terrane rocks beneath the obducted ophiolitic melange and the Qiangtang terrane to the north.

@article{doi1010292001tc001332,
    author = "Kapp, Paul and Murphy, Michael A. and Yin, An and Harrison, T. Mark and Ding, Lin and Guo, Jinghu",
    title = "Mesozoic and Cenozoic tectonic evolution of the Shiquanhe area of western Tibet",
    year = "2003",
    journal = "Tectonics",
    abstract = "In the Shiquanhe area of far‐western Tibet, mid‐Cretaceous strata lie unconformable on ophiolitic melange and Jurassic flysch associated with the Bangong‐Nujiang suture zone. On the basis of our mapping and geochronologic studies, we suggest that these Cretaceous strata were shortened by >57\% over a north south distance of 50 km during Late Cretaceous‐early Tertiary time. The Late Cretaceous Narangjiapo thrust placed Permian strata >20 km over ophiolitic melange and Cretaceous strata. North of the Narangjiapo thrust, >40 km of shortening was accommodated by the Late Cretaceous‐early Tertiary south directed Jaggang thrust system that involves Jurassic flysch and Cretaceous strata, and roots into a decollement within ophiolitic melange. The most recent shortening was accommodated to the south of the Narangjiapo thrust, along the north dipping Shiquanhe thrust. The Shiquanhe thrust cuts flat‐lying 22.6 ± 0.3 Ma volcanic rocks and underlying folded, Tertiary nonmarine strata in its footwall and was likely active during slip along the Oligocene Gangdese thrust system of southern Tibet. Ophiolitic melange and structurally overlying Jurassic flysch near Shiquanhe are interpreted to represent remnants of a subduction‐accretion complex and forearc basin, respectively, that were obducted southward onto the margin of the Lhasa terrane during Late Jurassic‐Early Cretaceous closure of the Bangong‐Nujiang Ocean. Subsequent imbrication of the obducted sheet could have produced the two east‐west trending belts of ophiolitic melanges, separated by ∼100 km, in western Tibet. Late Cretaceous‐early Tertiary thin‐skinned shortening may have been accommodated in the deeper crust by northward underthrusting and duplexing of Lhasa terrane rocks beneath the obducted ophiolitic melange and the Qiangtang terrane to the north.",
    url = "https://doi.org/10.1029/2001tc001332",
    doi = "10.1029/2001tc001332",
    openalex = "W2121843968",
    references = "doi1010291999tc900042, doi101130spe281p1"
}

Abstract Analysis of tectonic stress from the inversion of fault kinematic and earthquake focal mechanism data is routinely done using a wide variety of direct inversion, iterative and grid search methods. This paper discusses important aspects and new developments of the stress inversion methodology as the critical evaluation and interpretation of the results. The problems of data selection and separation into subsets, choice of optimization function, and the use of non-fault structural elements in stress inversion (tension, shear and compression fractures) are examined. The classical Right Dihedron method is developed in order to estimate the stress ratio R, widen its applicability to compression and tension fractures, and provide a compatibility test for data selection and separation. A new Rotational Optimization procedure for interactive kinematic data separation of fault-slip and focal mechanism data and progressive stress tensor optimization is presented. The quality assessment procedure defined for the World Stress Map project is extended in order to take into account the diversity of orientations of structural data used in the inversion. The range of stress regimes is expressed by a stress regime index R’, useful for regional comparisons and mapping. All these aspects have been implemented in a computer program TENSOR, which is introduced briefly. The procedures for determination of stress tensor using these new aspects are described using natural sets of fault-slip and focal mechanism data from the Baikal Rift Zone.

@article{doi101144gslsp20032120106,
    author = "Delvaux, Damien and Sperner, Blanka",
    title = "New aspects of tectonic stress inversion with reference to the TENSOR program",
    year = "2003",
    journal = "Geological Society London Special Publications",
    abstract = "Abstract Analysis of tectonic stress from the inversion of fault kinematic and earthquake focal mechanism data is routinely done using a wide variety of direct inversion, iterative and grid search methods. This paper discusses important aspects and new developments of the stress inversion methodology as the critical evaluation and interpretation of the results. The problems of data selection and separation into subsets, choice of optimization function, and the use of non-fault structural elements in stress inversion (tension, shear and compression fractures) are examined. The classical Right Dihedron method is developed in order to estimate the stress ratio R, widen its applicability to compression and tension fractures, and provide a compatibility test for data selection and separation. A new Rotational Optimization procedure for interactive kinematic data separation of fault-slip and focal mechanism data and progressive stress tensor optimization is presented. The quality assessment procedure defined for the World Stress Map project is extended in order to take into account the diversity of orientations of structural data used in the inversion. The range of stress regimes is expressed by a stress regime index R’, useful for regional comparisons and mapping. All these aspects have been implemented in a computer program TENSOR, which is introduced briefly. The procedures for determination of stress tensor using these new aspects are described using natural sets of fault-slip and focal mechanism data from the Baikal Rift Zone.",
    url = "https://doi.org/10.1144/gsl.sp.2003.212.01.06",
    doi = "10.1144/gsl.sp.2003.212.01.06",
    openalex = "W1985241918",
    references = "doi101007bf00876528, doi1010160040195195000909, doi1010160191814181900560, doi1010160191814185900483, doi1010160191814187901453, doi101016s0040195197002102, doi101017s0016756800059987, doi10102992jb00132, doi1011300016760619881001181piujot23co2, doi1011300091761319960240275staafr23co2, doi102113gssgfbulls7xix61309, doi105860choice320317"
}

A new regional compilation of the drainage history in southeastern Tibet suggests that the modern rivers draining the plateau margin were once tributaries to a single, southward flowing system which drained into the South China Sea. Disruption of the paleo‐drainage occurred by river capture and reversal prior to or coeval with the initiation of Miocene (?) uplift in eastern Tibet, including ∼2000 m of surface uplift of the lower plateau margin since reversal of the flow direction of the Yangtze River. Despite lateral changes in course due to capture and reversal, the superposition of eastward and southward draining rivers that cross the southeastern plateau margin suggests that uplift has occurred over long wavelengths (>1000 km), mimicking the present low‐gradient topographic slope. Thus reorganization of drainage lines by capture and reversal events explains most of the peculiar patterns of the eastern plateau rivers, without having to appeal to large‐magnitude tectonic shear.

@article{doi1010292002tc001402,
    author = "Clark, Marla D. and Schoenbohm, Lindsay M. and Royden, L. H. and Whipple, K. X. and Burchfiel, B. C. and Zhang, X. and Tang, Wenqing and Wang, E. and Chen, L.",
    title = "Surface uplift, tectonics, and erosion of eastern Tibet from large‐scale drainage patterns",
    year = "2004",
    journal = "Tectonics",
    abstract = "A new regional compilation of the drainage history in southeastern Tibet suggests that the modern rivers draining the plateau margin were once tributaries to a single, southward flowing system which drained into the South China Sea. Disruption of the paleo‐drainage occurred by river capture and reversal prior to or coeval with the initiation of Miocene (?) uplift in eastern Tibet, including ∼2000 m of surface uplift of the lower plateau margin since reversal of the flow direction of the Yangtze River. Despite lateral changes in course due to capture and reversal, the superposition of eastward and southward draining rivers that cross the southeastern plateau margin suggests that uplift has occurred over long wavelengths (>1000 km), mimicking the present low‐gradient topographic slope. Thus reorganization of drainage lines by capture and reversal events explains most of the peculiar patterns of the eastern plateau rivers, without having to appeal to large‐magnitude tectonic shear.",
    url = "https://doi.org/10.1029/2002tc001402",
    doi = "10.1029/2002tc001402",
    openalex = "W1543840266",
    references = "doi101016s0743954798000026, doi10102994wr00757, doi101046j1365246x199900802x"
}

Indian plate rocks in the central Himalaya have traditionally been divided into orogen‐parallel, fault‐bound tectonostratigraphic zones. A straightforward westward extrapolation of these zones has proved problematic in part because of a lack of consensus on the existence or significance of major faults within the metamorphic zone of the Indian plate in Pakistan where more than 10 locations for the Main Central thrust (MCT) have been proposed. We address this ambiguity by systematically tracing established central Himalayan tectonostratigraphy around the western Himalayan syntaxis and across Pakistan. This exercise reveals the following stratigraphic and structural relationships: (1) There is a westward decrease in Neogene shortening across the Himalayan fold and thrust belt such that there is no age equivalent thrust in Pakistan with displacement and metamorphic juxtaposition equivalent to the central Himalayan MCT. (2) Shortening across the fold and thrust belt in western Pakistan is concentrated in the unmetamorphosed foreland as opposed to the metamorphic zone in the central Himalaya. (3) Lesser Himalayan, Higher Himalayan, and Tethyan rocks are in stratigraphic order within the metamorphic zone of Pakistan which appears to be the metamorphic equivalent of Kashmir Tethyan stratigraphy. (4) The combination of early Paleozoic and late Paleozoic tectonism in Pakistan has locally eliminated Upper Proterozoic Higher Himalayan rock and lower to middle Paleozoic Tethyan rock from the metamorphic zone of Pakistan. (5) Late Cretaceous and/or early Paleocene proto‐Himalayan deformation in the Pakistan foreland telescoped and eroded stratigraphy prior to the main phase of Himalayan orogeny. (6) Tectonostratigraphic zones are offset in eastern Pakistan by the transverse Jhelum‐Balakot fault. (7) There is no evidence within the Indian plate of Pakistan for a large‐scale normal fault system comparable to the South Tibetan detachment system. (8) Stratigraphy, as well as the age and tectonic setting of deformation and metamorphism, must be taken into account when drawing tectonostratigraphic zones.

@article{doi1010292003tc001554,
    author = "DiPietro, Joseph A. and Pogue, Kevin R.",
    title = "Tectonostratigraphic subdivisions of the Himalaya: A view from the west",
    year = "2004",
    journal = "Tectonics",
    abstract = "Indian plate rocks in the central Himalaya have traditionally been divided into orogen‐parallel, fault‐bound tectonostratigraphic zones. A straightforward westward extrapolation of these zones has proved problematic in part because of a lack of consensus on the existence or significance of major faults within the metamorphic zone of the Indian plate in Pakistan where more than 10 locations for the Main Central thrust (MCT) have been proposed. We address this ambiguity by systematically tracing established central Himalayan tectonostratigraphy around the western Himalayan syntaxis and across Pakistan. This exercise reveals the following stratigraphic and structural relationships: (1) There is a westward decrease in Neogene shortening across the Himalayan fold and thrust belt such that there is no age equivalent thrust in Pakistan with displacement and metamorphic juxtaposition equivalent to the central Himalayan MCT. (2) Shortening across the fold and thrust belt in western Pakistan is concentrated in the unmetamorphosed foreland as opposed to the metamorphic zone in the central Himalaya. (3) Lesser Himalayan, Higher Himalayan, and Tethyan rocks are in stratigraphic order within the metamorphic zone of Pakistan which appears to be the metamorphic equivalent of Kashmir Tethyan stratigraphy. (4) The combination of early Paleozoic and late Paleozoic tectonism in Pakistan has locally eliminated Upper Proterozoic Higher Himalayan rock and lower to middle Paleozoic Tethyan rock from the metamorphic zone of Pakistan. (5) Late Cretaceous and/or early Paleocene proto‐Himalayan deformation in the Pakistan foreland telescoped and eroded stratigraphy prior to the main phase of Himalayan orogeny. (6) Tectonostratigraphic zones are offset in eastern Pakistan by the transverse Jhelum‐Balakot fault. (7) There is no evidence within the Indian plate of Pakistan for a large‐scale normal fault system comparable to the South Tibetan detachment system. (8) Stratigraphy, as well as the age and tectonic setting of deformation and metamorphism, must be taken into account when drawing tectonostratigraphic zones.",
    url = "https://doi.org/10.1029/2003tc001554",
    doi = "10.1029/2003tc001554",
    openalex = "W1615361574",
    references = "coward1986collision, doi1010160012821x82900073, doi1010292000tc001226, doi10102993tc01130, doi10102996tc01791, doi101130001676062000112324tothas20co2, doi101130spe269, doi1023071794401, doi102475ajs27511, openalexw614437925"
}

Abstract The metapelitic rocks of the Sikkim Himalayas show an inverted metamorphic sequence (IMS) of the complete Barrovian zones from chlorite to sillimanite + K‐feldspar, with the higher grade rocks appearing at progressively higher structural levels. Within the IMS, four groups of major planar structures, S 1, S 2 and S 3 were recognised. The S 2 structures are pervasive throughout the Barrovian sequence, and are sub‐parallel to the metamorphic isograds. The mineral growth in all zones is dominantly syn‐S 2. The disposition of the metamorphic zones and structural features show that the zones were folded as a northerly plunging antiform. Significant bulk compositional variation, with consequent changes of mineralogy, occurs even at the scale of a thin section in some garnet zone rocks. The results of detailed petrographic and thermobarometric studies of the metapelites along a roughly E–W transect show progressive increase of both pressure and temperature with increasing structural levels in the entire IMS. This is contrary to all models that call for thermal inversion as a possible reason for the origin of the IMS. Also, the observation of the temporal relation between crystallization and S 2 structures is problematic for models of post‐/late‐metamorphic tectonic inversion by recumbent folding or thrusting. A successful model of the IMS should explain the petrological coherence of the Barrovian zones and the close relationship of crystallization in each zone with S 2 planar structures along with the observed trend(s) of P–T variation in Sikkim and in other sections. A discussion is presented of some of the available models that, with some modifications, seem to be capable of explaining these observations.

@article{doi101111j15251314200400522x,
    author = "Dasgupta, Sayantan and Ganguly, Jibamitra and Neogi, Susobhan",
    title = "Inverted metamorphic sequence in the Sikkim Himalayas: crystallization history, P–T gradient and implications",
    year = "2004",
    journal = "Journal of Metamorphic Geology",
    abstract = "Abstract The metapelitic rocks of the Sikkim Himalayas show an inverted metamorphic sequence (IMS) of the complete Barrovian zones from chlorite to sillimanite + K‐feldspar, with the higher grade rocks appearing at progressively higher structural levels. Within the IMS, four groups of major planar structures, S 1, S 2 and S 3 were recognised. The S 2 structures are pervasive throughout the Barrovian sequence, and are sub‐parallel to the metamorphic isograds. The mineral growth in all zones is dominantly syn‐S 2. The disposition of the metamorphic zones and structural features show that the zones were folded as a northerly plunging antiform. Significant bulk compositional variation, with consequent changes of mineralogy, occurs even at the scale of a thin section in some garnet zone rocks. The results of detailed petrographic and thermobarometric studies of the metapelites along a roughly E–W transect show progressive increase of both pressure and temperature with increasing structural levels in the entire IMS. This is contrary to all models that call for thermal inversion as a possible reason for the origin of the IMS. Also, the observation of the temporal relation between crystallization and S 2 structures is problematic for models of post‐/late‐metamorphic tectonic inversion by recumbent folding or thrusting. A successful model of the IMS should explain the petrological coherence of the Barrovian zones and the close relationship of crystallization in each zone with S 2 planar structures along with the observed trend(s) of P–T variation in Sikkim and in other sections. A discussion is presented of some of the available models that, with some modifications, seem to be capable of explaining these observations.",
    url = "https://doi.org/10.1111/j.1525-1314.2004.00522.x",
    doi = "10.1111/j.1525-1314.2004.00522.x",
    openalex = "W1561347175"
}

Geochronological, structural, and sedimentological data provide the basis for a regional synthesis of the evolution of the Cordilleran retroarc thrust belt and foreland basin system in the western U.S.A. In this region, the Cordilleran orogenic belt became tectonically consolidated during Late Jurassic time (∼155 Ma) with the closure of marginal oceanic basins and accretion of fringing arcs along the western edge of the North American plate. Over the ensuing 100 Myr, contractile deformation propagated approximately 1000 kilometers eastward, culminating in the formation of the Laramide Rocky Mountain ranges. At the peak of its development, the retroarc side of the Cordillera was divided into five tectonomorphic zones, including from west to east the Luning-Fencemaker thrust belt; the central Nevada (or Eureka) thrust belt; a high-elevation plateau (the "Nevadaplano"); the topographically rugged Sevier fold-thrust belt; and the Laramide zone of intraforeland basement uplifts and basins. Mid-crustal rocks beneath the Nevadaplano experienced high-grade metamorphism and shortening during Late Jurassic and mid- to Late Cretaceous time, and the locus of major, upper crustal thrust faulting migrated sporadically eastward. By Late Cretaceous time, the middle crust beneath the Nevadaplano was experiencing decompression and cooling, perhaps in response to large-magnitude ductile extension and isostatic exhumation, concurrent with ongoing thrusting in the frontal Sevier belt. The tectonic history of the Sevier belt was remarkably consistent along strike of the orogenic belt, with emplacement of regional-scale Proterozoic and Paleozoic megathrust sheets during Early Cretaceous time and multiple, more closely spaced, Paleozoic and Mesozoic thrust sheets during Late Cretaceous--Paleocene time. Coeval with emplacement of the frontal thrust sheets, large structural culminations in Archean-Proterozoic crystalline basement developed along the basement step formed by Neoproterozoic rifting. A complex foreland basin system evolved in concert with the orogenic wedge. During its early and late history (∼155 - 110 Ma and ∼70 - 55 Ma) the basin was dominated by nonmarine deposition, whereas marine waters inundated the basin during its midlife (∼110 - 70 Ma). Late Jurassic basin development was controlled by both flexural and dynamic subsidence. From Early Cretaceous through early Late Cretaceous time the basin was dominated by flexural subsidence. From Late Cretaceous to mid-Cenozoic time the basin was increasingly partitioned by basement-involved Laramide structures. Linkages between Late Jurassic and Late Cretaceous Cordilleran arc-magmatism and westward underthrusting of North American continental lithosphere beneath the arc are not plainly demonstrable from the geological record in the Cordilleran thrust belt. A significant lag-time (∼20 Myr) between shortening and coeval underthrusting, on the one hand, and generation of arc melts, on the other, is required for any linkage to exist. However, inferred Late Jurassic lithospheric delamination may have provided a necessary precondition to allow relatively rapid Early Cretaceous continental underthrusting, which in turn could have catalyzed the Late Cretaceous arc flare-up.

@article{doi102475ajs3042105,
    author = "DeCelles, Peter G.",
    title = "Late Jurassic to Eocene evolution of the Cordilleran thrust belt and foreland basin system, western U.S.A.",
    year = "2004",
    journal = "American Journal of Science",
    abstract = {Geochronological, structural, and sedimentological data provide the basis for a regional synthesis of the evolution of the Cordilleran retroarc thrust belt and foreland basin system in the western U.S.A. In this region, the Cordilleran orogenic belt became tectonically consolidated during Late Jurassic time (∼155 Ma) with the closure of marginal oceanic basins and accretion of fringing arcs along the western edge of the North American plate. Over the ensuing 100 Myr, contractile deformation propagated approximately 1000 kilometers eastward, culminating in the formation of the Laramide Rocky Mountain ranges. At the peak of its development, the retroarc side of the Cordillera was divided into five tectonomorphic zones, including from west to east the Luning-Fencemaker thrust belt; the central Nevada (or Eureka) thrust belt; a high-elevation plateau (the "Nevadaplano"); the topographically rugged Sevier fold-thrust belt; and the Laramide zone of intraforeland basement uplifts and basins. Mid-crustal rocks beneath the Nevadaplano experienced high-grade metamorphism and shortening during Late Jurassic and mid- to Late Cretaceous time, and the locus of major, upper crustal thrust faulting migrated sporadically eastward. By Late Cretaceous time, the middle crust beneath the Nevadaplano was experiencing decompression and cooling, perhaps in response to large-magnitude ductile extension and isostatic exhumation, concurrent with ongoing thrusting in the frontal Sevier belt. The tectonic history of the Sevier belt was remarkably consistent along strike of the orogenic belt, with emplacement of regional-scale Proterozoic and Paleozoic megathrust sheets during Early Cretaceous time and multiple, more closely spaced, Paleozoic and Mesozoic thrust sheets during Late Cretaceous--Paleocene time. Coeval with emplacement of the frontal thrust sheets, large structural culminations in Archean-Proterozoic crystalline basement developed along the basement step formed by Neoproterozoic rifting. A complex foreland basin system evolved in concert with the orogenic wedge. During its early and late history (∼155 - 110 Ma and ∼70 - 55 Ma) the basin was dominated by nonmarine deposition, whereas marine waters inundated the basin during its midlife (∼110 - 70 Ma). Late Jurassic basin development was controlled by both flexural and dynamic subsidence. From Early Cretaceous through early Late Cretaceous time the basin was dominated by flexural subsidence. From Late Cretaceous to mid-Cenozoic time the basin was increasingly partitioned by basement-involved Laramide structures. Linkages between Late Jurassic and Late Cretaceous Cordilleran arc-magmatism and westward underthrusting of North American continental lithosphere beneath the arc are not plainly demonstrable from the geological record in the Cordilleran thrust belt. A significant lag-time (∼20 Myr) between shortening and coeval underthrusting, on the one hand, and generation of arc melts, on the other, is required for any linkage to exist. However, inferred Late Jurassic lithospheric delamination may have provided a necessary precondition to allow relatively rapid Early Cretaceous continental underthrusting, which in turn could have catalyzed the Late Cretaceous arc flare-up.},
    url = "https://doi.org/10.2475/ajs.304.2.105",
    doi = "10.2475/ajs.304.2.105",
    openalex = "W2135909516",
    references = "doi101016004019519390295u, doi10102993rg02030, doi101029jb075i014p02625, doi101029jb088ib02p01153, doi101029jb093ib04p03211, doi101029tc005i002p00227, doi101038270403a0, doi101038386061a0, doi101046j13652117199601491x, doi1011300016760619881001023papsol23co2, doi101130001676062000112324tothas20co2, doi101130dnaggnac2463, doi101130dnaggnag3261, doi101130mem151p355, doi101130spe206, doi101130spe206p1, doi1013062f9188fb16ce11d78645000102c1865d"
}

@article{doi101016jepsl200502038,
    author = "Leech, M. L. and Singh, Sandeep and Jain, Arvind Kumar and Klemperer, S. L. and Manickavasagam, R. M.",
    title = "The onset of India–Asia continental collision: Early, steep subduction required by the timing of UHP metamorphism in the western Himalaya",
    year = "2005",
    journal = "Earth and Planetary Science Letters",
    url = "https://doi.org/10.1016/j.epsl.2005.02.038",
    doi = "10.1016/j.epsl.2005.02.038",
    openalex = "W2112077113",
    references = "doi101016jepsl200408019, doi101016s0012821x99002770, doi101130spe281p1"
}

Empirical observations from fluvial systems across the globe reveal a consistent power-law scaling between channel slope and contributing drainage area. Theoretical arguments for both detachment- and transport-limited erosion regimes suggest that rock uplift rate should exert first-order control on this scaling. Here we describe in detail a method for exploiting this relationship, in which topographic indices of longitudinal profile shape and character are derived from digital topographic data. The stream profile data can then be used to delineate breaks in scaling that may be associated with tectonic boundaries. The description of the method is followed by three case studies from...

@incollection{doi1011302006239804,
    author = "Wobus, Cameron and Whipple, K. X. and Kirby, Eric and Snyder, Noah P. and Johnson, J. P. and Spyropolou, Katerina and Crosby, B. T. and Sheehan, Daniel",
    title = "Tectonics from topography: Procedures, promise, and pitfalls",
    year = "2006",
    booktitle = "Geological Society of America eBooks",
    abstract = "Empirical observations from fluvial systems across the globe reveal a consistent power-law scaling between channel slope and contributing drainage area. Theoretical arguments for both detachment- and transport-limited erosion regimes suggest that rock uplift rate should exert first-order control on this scaling. Here we describe in detail a method for exploiting this relationship, in which topographic indices of longitudinal profile shape and character are derived from digital topographic data. The stream profile data can then be used to delineate breaks in scaling that may be associated with tectonic boundaries. The description of the method is followed by three case studies from...",
    url = "https://doi.org/10.1130/2006.2398(04)",
    doi = "10.1130/2006.2398(04)",
    openalex = "W2225905194",
    references = "doi10102994wr00757, doi101038379505a0"
}

@article{doi101130b259111,
    author = "Robinson, Delores M. and DeCelles, Peter G. and Copeland, Peter",
    title = "Tectonic evolution of the Himalayan thrust belt in western Nepal: Implications for channel flow models",
    year = "2006",
    journal = "Geological Society of America Bulletin",
    url = "https://doi.org/10.1130/b25911.1",
    doi = "10.1130/b25911.1",
    openalex = "W2134254813",
    references = "doi101007bf01823808"
}

Results of clay mineralogy, major element geochemistry, and Sr and Nd isotopes in 93 argillaceous samples collected from drainage basins of the Pearl, Red, and Mekong rivers reveal different degrees of chemical weathering in Southeast Asia despite similar climate conditions across these regions. The kaolinite/illite ratio, illite chemistry index, and illite crystallinity can be used as indicators of chemical weathering intensity. These mineralogical proxies combined with the K 2 O/(Na 2 O + CaO) molar ratio, chemical index of alteration (CIA), and weathering trends observed from major element results indicate intensive silicate weathering in the Pearl River basin, moderate to intensive in the Mekong River basin, and moderate in the Red River basin. Although a significant modification of ɛNd(0) values in our riverine sediments during chemical weathering and transport is unlikely, 87 Sr/ 86 Sr ratios are controlled by various states of chemical weathering of high‐Sr minerals such as plagioclase (rich in Na and Ca) with a linear decrease trend from the Pearl, Mekong, to Red river basins. Our results suggest that it is not the warm climate with heavy monsoon precipitation but tectonics playing the most significant role in controlling weathering and erosion processes in south China and Indochina Peninsula. Strong physical erosion caused by tectonic activities and river incision along the eastern margin of the Tibetan Plateau and along the Red River fault system is responsible for high contents of primary minerals in the lowlands of Red and Mekong river basins.

@article{doi1010292006gc001490,
    author = "Liu, Zhifei and Colin, Christophe and Huang, Wei and Le, Khanh Phon and Tong, Shengqi and Chen, Zhong and Trentesaux, Alain",
    title = "Climatic and tectonic controls on weathering in south China and Indochina Peninsula: Clay mineralogical and geochemical investigations from the Pearl, Red, and Mekong drainage basins",
    year = "2007",
    journal = "Geochemistry Geophysics Geosystems",
    abstract = "Results of clay mineralogy, major element geochemistry, and Sr and Nd isotopes in 93 argillaceous samples collected from drainage basins of the Pearl, Red, and Mekong rivers reveal different degrees of chemical weathering in Southeast Asia despite similar climate conditions across these regions. The kaolinite/illite ratio, illite chemistry index, and illite crystallinity can be used as indicators of chemical weathering intensity. These mineralogical proxies combined with the K 2 O/(Na 2 O + CaO) molar ratio, chemical index of alteration (CIA), and weathering trends observed from major element results indicate intensive silicate weathering in the Pearl River basin, moderate to intensive in the Mekong River basin, and moderate in the Red River basin. Although a significant modification of ɛNd(0) values in our riverine sediments during chemical weathering and transport is unlikely, 87 Sr/ 86 Sr ratios are controlled by various states of chemical weathering of high‐Sr minerals such as plagioclase (rich in Na and Ca) with a linear decrease trend from the Pearl, Mekong, to Red river basins. Our results suggest that it is not the warm climate with heavy monsoon precipitation but tectonics playing the most significant role in controlling weathering and erosion processes in south China and Indochina Peninsula. Strong physical erosion caused by tectonic activities and river incision along the eastern margin of the Tibetan Plateau and along the Red River fault system is responsible for high contents of primary minerals in the lowlands of Red and Mekong river basins.",
    url = "https://doi.org/10.1029/2006gc001490",
    doi = "10.1029/2006gc001490",
    openalex = "W1935059050",
    references = "doi101016jepsl200511028"
}

The Mogok metamorphic belt (MMB) extends for over 1500 km along the western margin of the Shan‐Thai block, from the Andaman Sea north to the eastern Himalayan syntaxis. Previous geochronology has suggested that a long‐lasting Jurassic–early Cretaceous subduction‐related event resulted in emplacement of granodiorites and orthogneisses (171–120 Ma) and a poorly constrained Tertiary metamorphic event. On the basis of new U‐Pb isotope dilution thermal ionization mass spectrometry and U‐Th‐Pb laser ablation–multicollector–inductively coupled plasma mass spectrometer geochronology presented here, we propose two Tertiary metamorphic events affected the MMB in Burma. The first was a Paleocene event that ended with intrusion of crosscutting postkinematic biotite granite dikes at ∼59 Ma. A second metamorphic event spanned late Eocene to Oligocene (at least from 37, possibly 47, to 29 Ma). This resulted in the growth of metamorphic monazite at sillimanite grade, growth of zircon rims at 47–43 Ma, sillimanite + muscovite replacing older andalusite, and synmetamorphic melting producing garnet and tourmaline bearing leucogranites at 45.5 ± 0.6 Ma and 24.5 ± 0.7 Ma. These data imply high‐temperature sillimanite + muscovite metamorphism peaking at 680°C and 4.9 kbar between 45 and 33 Ma, to around 606–656°C and 4.4–4.8 kbar at 29.3 ± 0.5 Ma. The later metamorphic event is older than 24.5 ± 0.3 Ma, the age of leucogranites that crosscut all earlier fabrics. Our structural and geochronological data suggest that the MMB links north to the unexposed middle or lower crust rocks of the Lhasa terrane, south Tibet, and east to high‐grade metamorphic core complexes in northwest Thailand.

@article{doi1010292006tc002083,
    author = "Searle, M. P. and Noble, Stephen R. and Cottle, John M. and Waters, David J. and Mitchell, A. H. G. and Hlaing, Tin and Horstwood, Matthew",
    title = "Tectonic evolution of the Mogok metamorphic belt, Burma (Myanmar) constrained by U‐Th‐Pb dating of metamorphic and magmatic rocks",
    year = "2007",
    journal = "Tectonics",
    abstract = "The Mogok metamorphic belt (MMB) extends for over 1500 km along the western margin of the Shan‐Thai block, from the Andaman Sea north to the eastern Himalayan syntaxis. Previous geochronology has suggested that a long‐lasting Jurassic–early Cretaceous subduction‐related event resulted in emplacement of granodiorites and orthogneisses (171–120 Ma) and a poorly constrained Tertiary metamorphic event. On the basis of new U‐Pb isotope dilution thermal ionization mass spectrometry and U‐Th‐Pb laser ablation–multicollector–inductively coupled plasma mass spectrometer geochronology presented here, we propose two Tertiary metamorphic events affected the MMB in Burma. The first was a Paleocene event that ended with intrusion of crosscutting postkinematic biotite granite dikes at ∼59 Ma. A second metamorphic event spanned late Eocene to Oligocene (at least from 37, possibly 47, to 29 Ma). This resulted in the growth of metamorphic monazite at sillimanite grade, growth of zircon rims at 47–43 Ma, sillimanite + muscovite replacing older andalusite, and synmetamorphic melting producing garnet and tourmaline bearing leucogranites at 45.5 ± 0.6 Ma and 24.5 ± 0.7 Ma. These data imply high‐temperature sillimanite + muscovite metamorphism peaking at 680°C and 4.9 kbar between 45 and 33 Ma, to around 606–656°C and 4.4–4.8 kbar at 29.3 ± 0.5 Ma. The later metamorphic event is older than 24.5 ± 0.3 Ma, the age of leucogranites that crosscut all earlier fabrics. Our structural and geochronological data suggest that the MMB links north to the unexposed middle or lower crust rocks of the Lhasa terrane, south Tibet, and east to high‐grade metamorphic core complexes in northwest Thailand.",
    url = "https://doi.org/10.1029/2006tc002083",
    doi = "10.1029/2006tc002083",
    openalex = "W1937531169",
    references = "doi1010291999tc900042"
}

Based on a compilation of published sources, rocks referred to as adakites show the following geochemical and isotopic characteristics: SiO2 ≥56 wt percent, Al2O3 ≥15 wt percent, MgO normally <3 wt percent, Mg number ≈0.5, Sr ≥400 ppm, Y ≤18 ppm, Yb ≤1.9 ppm, Ni ≥20 ppm, Cr ≥30 ppm, Sr/Y ≥20, La/Yb ≥20, and 87Sr/86Sr ≤0.7045. Rocks with such compositions have been interpreted to be the products of hybridization of felsic partial melts from subducting oceanic crust with the peridotitic mantle wedge during ascent and are not primary magmas. High Mg andesites have been interpreted to be related to adakites by partial melting of asthenospheric peridotite contaminated by slab melts. The case for these petrogenetic models for adakites and high Mg andesites is best made in the Archean, when higher mantle geotherms resulted in subducting slabs potentially reaching partial melting temperatures at shallow depths before dehydration rendered the slab infusible. In the Phanerozoic these conditions were likely only met under certain special tectonic conditions, such as subduction of young (≤25-m.y.-old) oceanic crust. Key adakitic geochemical signatures, such as low Y and Yb concentrations and high Sr/Y and La/Yb ratios, can be generated in normal asthenosphere-derived tholeiitic to calc-alkaline arc magmas by common upper plate crustal interaction and crystal fractionation processes and do not require slab melting. An assessment of several arc volcanic suites from around the world shows that most adakite-like compositions are generated in this way and do not reflect source processes. Similarly, rare adakite-like intrusive rocks associated with some porphyry Cu deposits are the evolved products of extensive crustal-level processing of calc-alkaline basalt-andesite-dacite-rhyolite series magmas. If slab melts contribute to such magmas, their geochemical signatures would have been obliterated or rendered ambiguous by subsequent extensive open-system processes. In Archean terranes, where adakitic and high Al tonalite-trondhjemite-granodiorite (TTG) magma series rocks are more common, porphyry Cu deposits are rare and, where found, are associated with normal calc-alkaline suites rather than adakites. The two different magma series are compositionally distinct in terms of several major and trace element parameters. Common upper plate magmatic processes such as melting-assimilation-storage-homogenization (MASH) and assimilation-fractional-crystallization (AFC) affecting normal arc magmas can be demonstrated to explain the distinctive compositions of most adakite-like arc rocks, including high Mg andesites and especially those rare examples associated with porphyry Cu deposits. In contrast, slab melting can in most cases neither be proved nor disproved and is therefore unsatisfactory as a unique factor in porphyry Cu genesis.

@article{doi102113gsecongeo1024537,
    author = "Richards, Jeremy P. and Kerrich, R.",
    title = "Special Paper: Adakite-Like Rocks: Their Diverse Origins and Questionable Role in Metallogenesis",
    year = "2007",
    journal = "Economic Geology",
    abstract = "Based on a compilation of published sources, rocks referred to as adakites show the following geochemical and isotopic characteristics: SiO2 ≥56 wt percent, Al2O3 ≥15 wt percent, MgO normally <3 wt percent, Mg number ≈0.5, Sr ≥400 ppm, Y ≤18 ppm, Yb ≤1.9 ppm, Ni ≥20 ppm, Cr ≥30 ppm, Sr/Y ≥20, La/Yb ≥20, and 87Sr/86Sr ≤0.7045. Rocks with such compositions have been interpreted to be the products of hybridization of felsic partial melts from subducting oceanic crust with the peridotitic mantle wedge during ascent and are not primary magmas. High Mg andesites have been interpreted to be related to adakites by partial melting of asthenospheric peridotite contaminated by slab melts. The case for these petrogenetic models for adakites and high Mg andesites is best made in the Archean, when higher mantle geotherms resulted in subducting slabs potentially reaching partial melting temperatures at shallow depths before dehydration rendered the slab infusible. In the Phanerozoic these conditions were likely only met under certain special tectonic conditions, such as subduction of young (≤25-m.y.-old) oceanic crust. Key adakitic geochemical signatures, such as low Y and Yb concentrations and high Sr/Y and La/Yb ratios, can be generated in normal asthenosphere-derived tholeiitic to calc-alkaline arc magmas by common upper plate crustal interaction and crystal fractionation processes and do not require slab melting. An assessment of several arc volcanic suites from around the world shows that most adakite-like compositions are generated in this way and do not reflect source processes. Similarly, rare adakite-like intrusive rocks associated with some porphyry Cu deposits are the evolved products of extensive crustal-level processing of calc-alkaline basalt-andesite-dacite-rhyolite series magmas. If slab melts contribute to such magmas, their geochemical signatures would have been obliterated or rendered ambiguous by subsequent extensive open-system processes. In Archean terranes, where adakitic and high Al tonalite-trondhjemite-granodiorite (TTG) magma series rocks are more common, porphyry Cu deposits are rare and, where found, are associated with normal calc-alkaline suites rather than adakites. The two different magma series are compositionally distinct in terms of several major and trace element parameters. Common upper plate magmatic processes such as melting-assimilation-storage-homogenization (MASH) and assimilation-fractional-crystallization (AFC) affecting normal arc magmas can be demonstrated to explain the distinctive compositions of most adakite-like arc rocks, including high Mg andesites and especially those rare examples associated with porphyry Cu deposits. In contrast, slab melting can in most cases neither be proved nor disproved and is therefore unsatisfactory as a unique factor in porphyry Cu genesis.",
    url = "https://doi.org/10.2113/gsecongeo.102.4.537",
    doi = "10.2113/gsecongeo.102.4.537",
    openalex = "W2008456126",
    references = "doi1010160009254180901072, doi101016b0080437516030358, doi101016jgca200511008"
}

The Himalayan orogen has experienced intense Cenozoic deformation and widespread metamorphism, making it diffi cult to track its initial architecture and the subsequent deformation path during the Cenozoic India-Asia collision. To address this issue, we conducted structural mapping and U-Pb zircon geochronology across the Shillong Plateau, Mikir Hills, and Brahmaputra River Valley of northeastern India, located 30-100 km south of the eastern Himalaya. Our work reveals three episodes of igneous activity at ca. 1600 Ma, ca. 1100 Ma, and ca. 500 Ma, and three ductile-deformation events at ca. 1100 Ma, 520-500 Ma, and during the Cretaceous. The first two events were contractional, possibly induced by assembly of Rodinia and Eastern Gondwana, while the last event was extensional, possibly related to breakup of Gondwana. Because of its prox imity to the Himalaya, the occurrence of 500 Ma contractional deformation in northeastern India implies that any attempt to determine the magnitude of Cenozoic deformation across the Himalayan orogen using Proterozoic strata as marker beds must first remove the effect of early Paleozoic deformation. The lithostratigraphy of the Shillong Plateau established by this study and its correlation to the Himalayan units imply that the Greater Himalayan Crystalline Complex may be a tectonic mixture of Indian crystalline basement, its Proterozoic-Cambrian cover sequence and an early Paleozoic arc. Although the Shillong Plateau may be regarded as a rigid block in the Cenozoic, our work demonstrates that distributed active left-slip faulting dominates its interior, consistent with earthquake focal mechanisms and global positioning system velocity fields across the region. © 2010 Geological Society of America.

@article{doi101130b264601,
    author = "Yin, An and Dubey, C. S. and Webb, A. Alexander G. and Kelty, Thomas K. and Grove, Marty and Gehrels, George E. and Burgess, W. Paul",
    title = "Geologic correlation of the Himalayan orogen and Indian craton: Part 1. Structural geology, U-Pb zircon geochronology, and tectonic evolution of the Shillong Plateau and its neighboring regions in NE India",
    year = "2009",
    journal = "Geological Society of America Bulletin",
    abstract = "The Himalayan orogen has experienced intense Cenozoic deformation and widespread metamorphism, making it diffi cult to track its initial architecture and the subsequent deformation path during the Cenozoic India-Asia collision. To address this issue, we conducted structural mapping and U-Pb zircon geochronology across the Shillong Plateau, Mikir Hills, and Brahmaputra River Valley of northeastern India, located 30-100 km south of the eastern Himalaya. Our work reveals three episodes of igneous activity at ca. 1600 Ma, ca. 1100 Ma, and ca. 500 Ma, and three ductile-deformation events at ca. 1100 Ma, 520-500 Ma, and during the Cretaceous. The first two events were contractional, possibly induced by assembly of Rodinia and Eastern Gondwana, while the last event was extensional, possibly related to breakup of Gondwana. Because of its prox imity to the Himalaya, the occurrence of 500 Ma contractional deformation in northeastern India implies that any attempt to determine the magnitude of Cenozoic deformation across the Himalayan orogen using Proterozoic strata as marker beds must first remove the effect of early Paleozoic deformation. The lithostratigraphy of the Shillong Plateau established by this study and its correlation to the Himalayan units imply that the Greater Himalayan Crystalline Complex may be a tectonic mixture of Indian crystalline basement, its Proterozoic-Cambrian cover sequence and an early Paleozoic arc. Although the Shillong Plateau may be regarded as a rigid block in the Cenozoic, our work demonstrates that distributed active left-slip faulting dominates its interior, consistent with earthquake focal mechanisms and global positioning system velocity fields across the region. © 2010 Geological Society of America.",
    url = "https://doi.org/10.1130/b26460.1",
    doi = "10.1130/b26460.1",
    openalex = "W1969833428",
    references = "doi1010292003tc001554"
}

Despite being the largest active collisional orogen on Earth, the growth mechanism of the Himalaya remains uncertain. Current debate has focused on the role of dynamic inter action between tectonics and climate and mass exchanges between the Himalayan and Tibetan crust during Cenozoic India-Asia collision. A major uncertainty in the debate comes from the lack of geologic information on the eastern segment of the Himalayas from 91°E to 97°E, which makes up about one-quarter of the mountain belt. To address this issue, we conducted detailed field mapping, U-Pb zircon age dating, and 40Ar/39Ar thermo chronology along two geologic traverses at longitudes of 92°E and 94°E across the eastern Himalaya. Our dating indicates the region experienced magmatic events at 1745-1760 Ma, 825-878 Ma, 480-520 Ma, and 28-20 Ma. The first three events also occurred in the northeastern Indian craton, while the last is unique to the Hima laya. Correlation of magmatic events and age-equivalent lithologic units suggests that the eastern segment of the Himalaya was constructed in situ by basement-involved thrusting, which is inconsistent with the hypothesis of high-grade Himalaya rocks derived from Tibet via channel flow. The Main Central thrust in the eastern Himalaya forms the roof of a major thrust duplex; its northern part was initiated at ca. 13 Ma, while the southern part was initiated at ca. 10 Ma, as indicated by 40Ar/39Ar thermochronom etry. Crustal thickening of the Main Central thrust hanging wall was expressed by discrete ductile thrusting between 12 Ma and 7 Ma, overlapping in time with motion on the Main Central thrust below. Restoration of two possible geologic cross sections from one of our geologic traverses, where one assumes the existence of pre-Cenozoic deformation below the Himalaya and the other assumes flat-lying strata prior to the India-Asia collision, leads to estimated shortening of 775 km (~76% strain) and 515 km (~70% strain), respectively. We favor the presence of significant basement topog raphy below the eastern Himalaya based on projections of early Paleo zoic structures from the Shillong Plateau (i.e., the Central Shillong thrust) located ~50 km south of our study area. Since northeastern India and possibly the eastern Himalaya both experienced early Paleozoic contraction, the estimated shortening from this study may have resulted from a combined effect of early Paleozoic and Cenozoic deformation. © 2009 Geological Society of America.

@article{doi101130b264611,
    author = "Yin, An and Dubey, C. S. and Kelty, T.K. and Webb, A. Alexander G. and Harrison, T. Mark and Chou, Chih-Hsin and Célérier, Julien",
    title = "Geologic correlation of the Himalayan orogen and Indian craton: Part 2. Structural geology, geochronology, and tectonic evolution of the Eastern Himalaya",
    year = "2009",
    journal = "Geological Society of America Bulletin",
    abstract = "Despite being the largest active collisional orogen on Earth, the growth mechanism of the Himalaya remains uncertain. Current debate has focused on the role of dynamic inter action between tectonics and climate and mass exchanges between the Himalayan and Tibetan crust during Cenozoic India-Asia collision. A major uncertainty in the debate comes from the lack of geologic information on the eastern segment of the Himalayas from 91°E to 97°E, which makes up about one-quarter of the mountain belt. To address this issue, we conducted detailed field mapping, U-Pb zircon age dating, and 40Ar/39Ar thermo chronology along two geologic traverses at longitudes of 92°E and 94°E across the eastern Himalaya. Our dating indicates the region experienced magmatic events at 1745-1760 Ma, 825-878 Ma, 480-520 Ma, and 28-20 Ma. The first three events also occurred in the northeastern Indian craton, while the last is unique to the Hima laya. Correlation of magmatic events and age-equivalent lithologic units suggests that the eastern segment of the Himalaya was constructed in situ by basement-involved thrusting, which is inconsistent with the hypothesis of high-grade Himalaya rocks derived from Tibet via channel flow. The Main Central thrust in the eastern Himalaya forms the roof of a major thrust duplex; its northern part was initiated at ca. 13 Ma, while the southern part was initiated at ca. 10 Ma, as indicated by 40Ar/39Ar thermochronom etry. Crustal thickening of the Main Central thrust hanging wall was expressed by discrete ductile thrusting between 12 Ma and 7 Ma, overlapping in time with motion on the Main Central thrust below. Restoration of two possible geologic cross sections from one of our geologic traverses, where one assumes the existence of pre-Cenozoic deformation below the Himalaya and the other assumes flat-lying strata prior to the India-Asia collision, leads to estimated shortening of 775 km (\textasciitilde 76\% strain) and 515 km (\textasciitilde 70\% strain), respectively. We favor the presence of significant basement topog raphy below the eastern Himalaya based on projections of early Paleo zoic structures from the Shillong Plateau (i.e., the Central Shillong thrust) located \textasciitilde 50 km south of our study area. Since northeastern India and possibly the eastern Himalaya both experienced early Paleozoic contraction, the estimated shortening from this study may have resulted from a combined effect of early Paleozoic and Cenozoic deformation. © 2009 Geological Society of America.",
    url = "https://doi.org/10.1130/b26461.1",
    doi = "10.1130/b26461.1",
    openalex = "W2069716890",
    references = "doi101016s1367912099000474, doi1010292003tc001554"
}

Two end‐member kinematic models of crustal shortening across the Himalaya are currently debated: one assumes localized thrusting along a single major thrust fault, the Main Himalayan Thrust (MHT) with nonuniform underplating due to duplexing, and the other advocates for out‐of‐sequence (OOS) thrusting in addition to thrusting along the MHT and underplating. We assess these two models based on the modeling of thermochronological, thermometric, and thermobarometric data from the central Nepal Himalaya. We complement a data set compiled from the literature with 114 40 Ar/ 39 Ar, 10 apatite fission track, and 5 zircon (U‐Th)/He thermochronological data. The data are predicted using a thermokinematic model (PECUBE), and the model parameters are constrained using an inverse approach based on the Neighborhood Algorithm. The model parameters include geometric characteristics as well as overthrusting rates, radiogenic heat production in the High Himalayan Crystalline (HHC) sequence, the age of initiation of the duplex or of out‐of‐sequence thrusting. Both models can provide a satisfactory fit to the inverted data. However, the model with out‐of‐sequence thrusting implies an unrealistic convergence rate ≥30 mm yr −1. The out‐of‐sequence thrust model can be adjusted to fit the convergence rate and the thermochronological data if the Main Central Thrust zone is assigned a constant geometry and a dip angle of about 30° and a slip rate of <1 mm yr −1. In the duplex model, the 20 mm yr −1 convergence rate is partitioned between an overthrusting rate of 5.8 ± 1.4 mm yr −1 and an underthrusting rate of 14.2 ± 1.8 mm yr −1. Modern rock uplift rates are estimated to increase from about 0.9 ± 0.31 mm yr −1 in the Lesser Himalaya to 3.0 ± 0.9 mm yr −1 at the front of the high range, 86 ± 13 km from the Main Frontal Thrust. The effective friction coefficient is estimated to be 0.07 or smaller, and the radiogenic heat production of HHC units is estimated to be 2.2 ± 0.1 μ W m −3. The midcrustal duplex initiated at 9.8 ± 1.7 Ma, leading to an increase of uplift rate at front of the High Himalaya from 0.9 ± 0.31 to 3.05 ± 0.9 mm yr −1. We also run 3‐D models by coupling PECUBE with a landscape evolution model (CASCADE). This modeling shows that the effect of the evolving topography can explain a fraction of the scatter observed in the data but not all of it, suggesting that lateral variations of the kinematics of crustal deformation and exhumation are likely. It has been argued that the steep physiographic transition at the foot of the Greater Himalayan Sequence indicates OOS thrusting, but our results demonstrate that the best fit duplex model derived from the thermochronological and thermobarometric data reproduces the present morphology of the Nepal Himalaya equally well.

@article{doi1010292008jb006126,
    author = "Herman, Frédéric and Copeland, Peter and Avouac, Jean‐Philippe and Bollinger, Laurent and Mahéo, Gweltaz and Fort, Patrick Le and Rai, SantaMan and Foster, David A. and Pêcher, Arnaud and Stüwe, Kurt and Henry, Pierre",
    title = "Exhumation, crustal deformation, and thermal structure of the Nepal Himalaya derived from the inversion of thermochronological and thermobarometric data and modeling of the topography",
    year = "2010",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "Two end‐member kinematic models of crustal shortening across the Himalaya are currently debated: one assumes localized thrusting along a single major thrust fault, the Main Himalayan Thrust (MHT) with nonuniform underplating due to duplexing, and the other advocates for out‐of‐sequence (OOS) thrusting in addition to thrusting along the MHT and underplating. We assess these two models based on the modeling of thermochronological, thermometric, and thermobarometric data from the central Nepal Himalaya. We complement a data set compiled from the literature with 114 40 Ar/ 39 Ar, 10 apatite fission track, and 5 zircon (U‐Th)/He thermochronological data. The data are predicted using a thermokinematic model (PECUBE), and the model parameters are constrained using an inverse approach based on the Neighborhood Algorithm. The model parameters include geometric characteristics as well as overthrusting rates, radiogenic heat production in the High Himalayan Crystalline (HHC) sequence, the age of initiation of the duplex or of out‐of‐sequence thrusting. Both models can provide a satisfactory fit to the inverted data. However, the model with out‐of‐sequence thrusting implies an unrealistic convergence rate ≥30 mm yr −1. The out‐of‐sequence thrust model can be adjusted to fit the convergence rate and the thermochronological data if the Main Central Thrust zone is assigned a constant geometry and a dip angle of about 30° and a slip rate of <1 mm yr −1. In the duplex model, the 20 mm yr −1 convergence rate is partitioned between an overthrusting rate of 5.8 ± 1.4 mm yr −1 and an underthrusting rate of 14.2 ± 1.8 mm yr −1. Modern rock uplift rates are estimated to increase from about 0.9 ± 0.31 mm yr −1 in the Lesser Himalaya to 3.0 ± 0.9 mm yr −1 at the front of the high range, 86 ± 13 km from the Main Frontal Thrust. The effective friction coefficient is estimated to be 0.07 or smaller, and the radiogenic heat production of HHC units is estimated to be 2.2 ± 0.1 μ W m −3. The midcrustal duplex initiated at 9.8 ± 1.7 Ma, leading to an increase of uplift rate at front of the High Himalaya from 0.9 ± 0.31 to 3.05 ± 0.9 mm yr −1. We also run 3‐D models by coupling PECUBE with a landscape evolution model (CASCADE). This modeling shows that the effect of the evolving topography can explain a fraction of the scatter observed in the data but not all of it, suggesting that lateral variations of the kinematics of crustal deformation and exhumation are likely. It has been argued that the steep physiographic transition at the foot of the Greater Himalayan Sequence indicates OOS thrusting, but our results demonstrate that the best fit duplex model derived from the thermochronological and thermobarometric data reproduces the present morphology of the Nepal Himalaya equally well.",
    url = "https://doi.org/10.1029/2008jb006126",
    doi = "10.1029/2008jb006126",
    openalex = "W2030721727",
    references = "doi101016jepsl200511028"
}

@article{doi101016jrse201012016,
    author = "Bertoldi, Luca and Massironi, Matteo and Visonà, Dario and Carosi, Rodolfo and Montomoli, Chiara and Gubert, Francesco and Naletto, G. and Pelizzo, Maria Guglielmina",
    title = "Mapping the Buraburi granite in the Himalaya of Western Nepal: Remote sensing analysis in a collisional belt with vegetation cover and extreme variation of topography",
    year = "2011",
    journal = "Remote Sensing of Environment",
    url = "https://doi.org/10.1016/j.rse.2010.12.016",
    doi = "10.1016/j.rse.2010.12.016",
    openalex = "W2079244709",
    references = "doi1010079783709157923, openalexw2182411511"
}

-parallel extension is an important component of the active deformation of the Himalaya. This extension is accommodated via arc-perpendicular normal faults linked to arc-parallel strike-slip faults. Analysis of ~130 global positioning system geodetic velocities indicates >3 cm yr -1 of arc-parallel extension of the Himalaya. Several models have sought to explain Himalayan arc-parallel extension and strike-slip faulting, including lateral extrusion of Tibet, oroclinal bending of the Himalaya, radial spreading of Tibet and the Himalaya, and variably oblique convergence between India and the Himalaya. Predictions of each model are tested against structural and geodetic observations. These tests indicate that the oblique convergence model best describes Himalayan extensional and strike-slip deformation.

@article{doi101130ges006061,
    author = "Styron, Richard and Taylor, Michael H. and Murphy, Michael A.",
    title = "Oblique convergence, arc-parallel extension, and the role of strike-slip faulting in the High Himalaya",
    year = "2011",
    journal = "Geosphere",
    abstract = "-parallel extension is an important component of the active deformation of the Himalaya. This extension is accommodated via arc-perpendicular normal faults linked to arc-parallel strike-slip faults. Analysis of \textasciitilde 130 global positioning system geodetic velocities indicates >3 cm yr -1 of arc-parallel extension of the Himalaya. Several models have sought to explain Himalayan arc-parallel extension and strike-slip faulting, including lateral extrusion of Tibet, oroclinal bending of the Himalaya, radial spreading of Tibet and the Himalaya, and variably oblique convergence between India and the Himalaya. Predictions of each model are tested against structural and geodetic observations. These tests indicate that the oblique convergence model best describes Himalayan extensional and strike-slip deformation.",
    url = "https://doi.org/10.1130/ges00606.1",
    doi = "10.1130/ges00606.1",
    openalex = "W2082527391"
}

We document geodetic strain across the Nepal Himalaya using GPS times series from 30 stations in Nepal and southern Tibet, in addition to previously published campaign GPS points and leveling data and determine the pattern of interseismic coupling on the Main Himalayan Thrust fault (MHT). The noise on the daily GPS positions is modeled as a combination of white and colored noise, in order to infer secular velocities at the stations with consistent uncertainties. We then locate the pole of rotation of the Indian plate in the ITRF 2005 reference frame at longitude = − 1.34° ± 3.31°, latitude = 51.4° ± 0.3° with an angular velocity of Ω = 0.5029 ± 0.0072°/Myr. The pattern of coupling on the MHT is computed on a fault dipping 10° to the north and whose strike roughly follows the arcuate shape of the Himalaya. The model indicates that the MHT is locked from the surface to a distance of approximately 100 km down dip, corresponding to a depth of 15 to 20 km. In map view, the transition zone between the locked portion of the MHT and the portion which is creeping at the long term slip rate seems to be at the most a few tens of kilometers wide and coincides with the belt of midcrustal microseismicity underneath the Himalaya. According to a previous study based on thermokinematic modeling of thermochronological and thermobarometric data, this transition seems to happen in a zone where the temperature reaches 350°C. The convergence between India and South Tibet proceeds at a rate of 17.8 ± 0.5 mm/yr in central and eastern Nepal and 20.5 ± 1 mm/yr in western Nepal. The moment deficit due to locking of the MHT in the interseismic period accrues at a rate of 6.6 ± 0.4 × 10 19 Nm/yr on the MHT underneath Nepal. For comparison, the moment released by the seismicity over the past 500 years, including 14 M W ≥ 7 earthquakes with moment magnitudes up to 8.5, amounts to only 0.9 × 10 19 Nm/yr, indicating a large deficit of seismic slip over that period or very infrequent large slow slip events. No large slow slip event has been observed however over the 20 years covered by geodetic measurements in the Nepal Himalaya. We discuss the magnitude and return period of M > 8 earthquakes required to balance the long term slip budget on the MHT.

@article{doi1010292011jb009071,
    author = "Ader, Thomas and Avouac, Jean‐Philippe and Liu‐Zeng, Jing and Lyon‐Caen, H. and Bollinger, Laurent and Galetzka, J. and Genrich, Jeff and Thomas, Marion Y. and Chanard, Kristel and Sapkota, Soma Nath and Rajaure, Sudhir and Shrestha, Prithvi and Ding, Lin and Flouzat, M.",
    title = "Convergence rate across the Nepal Himalaya and interseismic coupling on the Main Himalayan Thrust: Implications for seismic hazard",
    year = "2012",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "We document geodetic strain across the Nepal Himalaya using GPS times series from 30 stations in Nepal and southern Tibet, in addition to previously published campaign GPS points and leveling data and determine the pattern of interseismic coupling on the Main Himalayan Thrust fault (MHT). The noise on the daily GPS positions is modeled as a combination of white and colored noise, in order to infer secular velocities at the stations with consistent uncertainties. We then locate the pole of rotation of the Indian plate in the ITRF 2005 reference frame at longitude = − 1.34° ± 3.31°, latitude = 51.4° ± 0.3° with an angular velocity of Ω = 0.5029 ± 0.0072°/Myr. The pattern of coupling on the MHT is computed on a fault dipping 10° to the north and whose strike roughly follows the arcuate shape of the Himalaya. The model indicates that the MHT is locked from the surface to a distance of approximately 100 km down dip, corresponding to a depth of 15 to 20 km. In map view, the transition zone between the locked portion of the MHT and the portion which is creeping at the long term slip rate seems to be at the most a few tens of kilometers wide and coincides with the belt of midcrustal microseismicity underneath the Himalaya. According to a previous study based on thermokinematic modeling of thermochronological and thermobarometric data, this transition seems to happen in a zone where the temperature reaches 350°C. The convergence between India and South Tibet proceeds at a rate of 17.8 ± 0.5 mm/yr in central and eastern Nepal and 20.5 ± 1 mm/yr in western Nepal. The moment deficit due to locking of the MHT in the interseismic period accrues at a rate of 6.6 ± 0.4 × 10 19 Nm/yr on the MHT underneath Nepal. For comparison, the moment released by the seismicity over the past 500 years, including 14 M W ≥ 7 earthquakes with moment magnitudes up to 8.5, amounts to only 0.9 × 10 19 Nm/yr, indicating a large deficit of seismic slip over that period or very infrequent large slow slip events. No large slow slip event has been observed however over the 20 years covered by geodetic measurements in the Nepal Himalaya. We discuss the magnitude and return period of M > 8 earthquakes required to balance the long term slip budget on the MHT.",
    url = "https://doi.org/10.1029/2011jb009071",
    doi = "10.1029/2011jb009071",
    openalex = "W2024423630",
    references = "doi101007s0019000600303, doi10102995jb00862"
}

Abstract GPS data reveal that the Brahmaputra Valley has broken from the Indian Plate and rotates clockwise relative to India about a point a few hundred kilometers west of the Shillong Plateau. The GPS velocity vectors define two distinct blocks separated by the Kopili fault upon which 2–3 mm/yr of dextral slip is observed: the Shillong block between longitudes 89 and 93°E rotating clockwise at 1.15°/Myr and the Assam block from 93.5°E to 97°E rotating at ≈1.13°/Myr. These two blocks are more than 120 km wide in a north‐south sense, but they extend locally a similar distance beneath the Himalaya and Tibet. A result of these rotations is that convergence across the Himalaya east of Sikkim decreases in velocity eastward from 18 to ≈12 mm/yr and convergence between the Shillong Plateau and Bangladesh across the Dauki fault increases from 3 mm/yr in the west to >8 mm/yr in the east. This fast convergence rate is inconsistent with inferred geological uplift rates on the plateau (if a 45°N dip is assumed for the Dauki fault) unless clockwise rotation of the Shillong block has increased substantially in the past 4–8 Myr. Such acceleration is consistent with the reported recent slowing in the convergence rate across the Bhutan Himalaya. The current slip potential near Bhutan, based on present‐day convergence rates and assuming no great earthquake since 1713 A.D., is now ~5.4 m, similar to the slip reported from alluvial terraces that offsets across the Main Himalayan Thrust and sufficient to sustain a M w ≥ 8.0 earthquake in this area.

@article{doi1010022014jb011196,
    author = "Vernant, Philippe and Bilham, Roger and Szeliga, Walter and Drupka, Dowchu and Kalita, S. and Bhattacharyya, Anjan K. and Gaur, V. K. and Pelgay, Phuntsho and Cattin, Rodolphe and Berthet, Théo",
    title = "Clockwise rotation of the Brahmaputra Valley relative to India: Tectonic convergence in the eastern Himalaya, Naga Hills, and Shillong Plateau",
    year = "2014",
    journal = "Journal of Geophysical Research Solid Earth",
    abstract = "Abstract GPS data reveal that the Brahmaputra Valley has broken from the Indian Plate and rotates clockwise relative to India about a point a few hundred kilometers west of the Shillong Plateau. The GPS velocity vectors define two distinct blocks separated by the Kopili fault upon which 2–3 mm/yr of dextral slip is observed: the Shillong block between longitudes 89 and 93°E rotating clockwise at 1.15°/Myr and the Assam block from 93.5°E to 97°E rotating at ≈1.13°/Myr. These two blocks are more than 120 km wide in a north‐south sense, but they extend locally a similar distance beneath the Himalaya and Tibet. A result of these rotations is that convergence across the Himalaya east of Sikkim decreases in velocity eastward from 18 to ≈12 mm/yr and convergence between the Shillong Plateau and Bangladesh across the Dauki fault increases from 3 mm/yr in the west to >8 mm/yr in the east. This fast convergence rate is inconsistent with inferred geological uplift rates on the plateau (if a 45°N dip is assumed for the Dauki fault) unless clockwise rotation of the Shillong block has increased substantially in the past 4–8 Myr. Such acceleration is consistent with the reported recent slowing in the convergence rate across the Bhutan Himalaya. The current slip potential near Bhutan, based on present‐day convergence rates and assuming no great earthquake since 1713 A.D., is now \textasciitilde 5.4 m, similar to the slip reported from alluvial terraces that offsets across the Main Himalayan Thrust and sufficient to sustain a M w ≥ 8.0 earthquake in this area.",
    url = "https://doi.org/10.1002/2014jb011196",
    doi = "10.1002/2014jb011196",
    openalex = "W1533675099",
    references = "doi101038ngeo1669"
}

Abstract Siliciclastic sedimentary rocks derived from the southern Lhasa terrane, sitting depositionally upon rocks of the northern Indian passive continental margin, provide an estimate of the age of initial contact between the continental parts of the Indian and Asian plates. We report sedimentological, sedimentary petrological, and geochronological data from Upper Cretaceous‐Paleocene strata in the Sangdanlin section, located along the southern flank of the Indus‐Yarlung suture zone in southern Tibet. This is probably the most proximal, and therefore the oldest, record of the India‐Asia collision. These strata were deposited by high‐density turbidity currents (or concentrated density flows) and suspension settling of pelagic biogenic debris in a deep‐marine setting. An abrupt change from quartz‐arenitic to feldspatholithic sandstone compositions marks the transition from Indian to Asian sediment provenance. The abrupt compositional change is accompanied by changes in U‐Pb ages of detrital zircons diagnostic of a sediment provenance reversal, from Indian to Asian sources. The timing of the transition is bracketed between ~60 Ma and 58.5 ± 0.6 Ma by detrital zircon U‐Pb ages and zircon U‐Pb ages from a tuffaceous bed in the upper part of the section. In the context of a palinspastically restored regional paleogeographic framework, data from the Sangdanlin section combined with previously published data from the northern Tethyan Himalaya and the frontal Nepalese Lesser Himalaya and Subhimalaya suggest that a flexural wave migrated ~1300 km southward across what is now the Himalayan thrust belt from Paleocene time to the present.

@article{doi1010022014tc003522,
    author = "DeCelles, Peter G. and Kapp, Paul and Gehrels, George E. and Ding, Lin",
    title = "Paleocene‐Eocene foreland basin evolution in the Himalaya of southern Tibet and Nepal: Implications for the age of initial India‐Asia collision",
    year = "2014",
    journal = "Tectonics",
    abstract = "Abstract Siliciclastic sedimentary rocks derived from the southern Lhasa terrane, sitting depositionally upon rocks of the northern Indian passive continental margin, provide an estimate of the age of initial contact between the continental parts of the Indian and Asian plates. We report sedimentological, sedimentary petrological, and geochronological data from Upper Cretaceous‐Paleocene strata in the Sangdanlin section, located along the southern flank of the Indus‐Yarlung suture zone in southern Tibet. This is probably the most proximal, and therefore the oldest, record of the India‐Asia collision. These strata were deposited by high‐density turbidity currents (or concentrated density flows) and suspension settling of pelagic biogenic debris in a deep‐marine setting. An abrupt change from quartz‐arenitic to feldspatholithic sandstone compositions marks the transition from Indian to Asian sediment provenance. The abrupt compositional change is accompanied by changes in U‐Pb ages of detrital zircons diagnostic of a sediment provenance reversal, from Indian to Asian sources. The timing of the transition is bracketed between \textasciitilde 60 Ma and 58.5 ± 0.6 Ma by detrital zircon U‐Pb ages and zircon U‐Pb ages from a tuffaceous bed in the upper part of the section. In the context of a palinspastically restored regional paleogeographic framework, data from the Sangdanlin section combined with previously published data from the northern Tethyan Himalaya and the frontal Nepalese Lesser Himalaya and Subhimalaya suggest that a flexural wave migrated \textasciitilde 1300 km southward across what is now the Himalayan thrust belt from Paleocene time to the present.",
    url = "https://doi.org/10.1002/2014tc003522",
    doi = "10.1002/2014tc003522",
    openalex = "W1944076124",
    references = "doi10100797814684827684, doi101007bf02431072, doi101007bf02440107, doi101016jearscirev200405001, doi101016jearscirev200505004, doi101016jepsl200408019, doi101016jepsl200511028, doi101016jepsl200909013, doi1010292007gc001805, doi1010292011tc002868, doi101029eo064i011p0010601, doi101046j1365246x199900802x, doi101046j13653091200100360x, doi101111j13653091201201353x, doi101126science1894201419, doi10113000167606197586737gfmfrc20co2, doi10113000167606198394222ponaps20co2, doi101146annurevearth281211, doi101306212f7f312b2411d78648000102c1865d, normark1978fan, openalexw1570283708"
}

This paper reviews the tectonic, magmatic, and metallogenic history of the Tethyan orogen from the Carpathians to Indochina. Focus is placed on the formation of porphyry Cu ± Mo ± Au deposits, as being the most characteristic mineral deposit type formed during both subduction and collisional processes in this region. Relatively little is known about the history of the Paleotethys ocean, which opened and closed between Gondwana and Eurasia in the Paleozoic, and few ore deposits are preserved from this period. The Neotethyan ocean opened in the Permian–Early Triassic as the Cimmerian continental fragments (the cores of Turkey, Iran, Tibet, and Indochina) rifted from the northern Gondwana margin and drifted northwards. These microcontinents docked with the Eurasian margin at various points in the Mesozoic and Cenozoic, and formed a complex archipelago involving several small back-arc basins and remnants of the Paleotethyan ocean. The main Neotethyan ocean and these smaller basins were largely eliminated by collision with India and Africa–Arabia in the early Eocene and early-mid Miocene, respectively, although Neotethyan subduction continues beneath the Hellenic arc and the Makran. The majority of porphyry-type deposits are found in association with Neotethyan subduction (mainly in the Mesozoic and Paleogene), and syn- to post-collisional events in the mid-Paleogene to Neogene. They are found throughout the orogen, but some sections are particularly well-endowed, including the Carpathians–Balkans–Rhodopes, eastern Turkey–Lesser Caucasus–NW Iran, SE Iran–SW Pakistan, southern Tibet, and SE Tibet–Indochina. Other sections that appear barren may reflect deeper levels of erosion, young sedimentary cover, or lack of exploration, although there may also be real reasons for low prospectivity in some areas, such as minimal subduction (e.g., the western Mediterranean region) or lithospheric underthrusting (as proposed in western Tibet). Over the last decade, improved geochronological constraints on the timing of ore formation and key tectonic events have revealed that many porphyry deposits that were previously assumed to be subduction-related are in fact broadly collision-related, some forming in back-arc settings in advance of collision, some during collision, and others during post-collisional processes such as orogenic collapse and/or delamination of subcontinental mantle lithosphere. While the formation of subduction-related porphyries is quite well understood, collisional metallogeny is more complex, and may involve a number of different processes or sources. These include melting of: orogenically thickened crust; previously subduction-modified lithosphere (including metasomatized mantle, underplated mafic rocks, or lower crustal arc plutons and cumulates); or upwelling asthenosphere (e.g., in response to delamination, slab breakoff, back-arc extension, or orogenic collapse). The most fertile sources for syn- and post-collisional porphyry deposits appear to be subduction-modified lithosphere, because these hydrated lithologies melt at relatively low temperatures during later tectonomagmatic events, and retain the oxidized and relatively metalliferous character of the original arc magmatism. Unusually metallically enriched lithospheric sources do not seem to be required, but the amount of residual sulfide phases in these rocks may control metal ratios (e.g., Cu:Au) in subsequent magmatic hydrothermal ore deposits. Relatively Au-rich deposits potentially form in these settings, as observed in the Carpathians (e.g., Roşia Montană), Turkey (Kisladag, Çöpler), and Iran (Sari Gunay, Dalli), although the majority of syn- and post-collisional porphyries are Cu–Mo-rich, and resemble normal subduction-related deposits (e.g., in the Gangdese belt of southern Tibet). This similarity extends to the associated igneous rocks, which, being derived from subduction-modified sources, largely retain the geochemical and isotopic character of those original arc magmas. While still retaining a broadly calc-alkaline character, these rocks may extend to mildly alkaline (shoshonitic) compositions, and may display adakite-like trace element signatures (high Sr/Y and La/Yb ratios) reflecting melting of deep crustal garnet amphibolitic sources. But they are otherwise hard to distinguish from normal subduction-related magmas. Small, post-collisional mafic, alkaline volcanic centers are common throughout the orogen, but for the most part appear to be barren. However, similar rocks in other post-subduction settings around the world are associated with important alkalic-type porphyry and epithermal Au ± Cu deposits, and the potential for discovery of such deposits in the Tethyan orogen should not be overlooked.

@article{doi101016joregeorev201411009,
    author = "Richards, Jeremy P.",
    title = "Tectonic, magmatic, and metallogenic evolution of the Tethyan orogen: From subduction to collision",
    year = "2014",
    journal = "Ore Geology Reviews",
    abstract = "This paper reviews the tectonic, magmatic, and metallogenic history of the Tethyan orogen from the Carpathians to Indochina. Focus is placed on the formation of porphyry Cu ± Mo ± Au deposits, as being the most characteristic mineral deposit type formed during both subduction and collisional processes in this region. Relatively little is known about the history of the Paleotethys ocean, which opened and closed between Gondwana and Eurasia in the Paleozoic, and few ore deposits are preserved from this period. The Neotethyan ocean opened in the Permian–Early Triassic as the Cimmerian continental fragments (the cores of Turkey, Iran, Tibet, and Indochina) rifted from the northern Gondwana margin and drifted northwards. These microcontinents docked with the Eurasian margin at various points in the Mesozoic and Cenozoic, and formed a complex archipelago involving several small back-arc basins and remnants of the Paleotethyan ocean. The main Neotethyan ocean and these smaller basins were largely eliminated by collision with India and Africa–Arabia in the early Eocene and early-mid Miocene, respectively, although Neotethyan subduction continues beneath the Hellenic arc and the Makran. The majority of porphyry-type deposits are found in association with Neotethyan subduction (mainly in the Mesozoic and Paleogene), and syn- to post-collisional events in the mid-Paleogene to Neogene. They are found throughout the orogen, but some sections are particularly well-endowed, including the Carpathians–Balkans–Rhodopes, eastern Turkey–Lesser Caucasus–NW Iran, SE Iran–SW Pakistan, southern Tibet, and SE Tibet–Indochina. Other sections that appear barren may reflect deeper levels of erosion, young sedimentary cover, or lack of exploration, although there may also be real reasons for low prospectivity in some areas, such as minimal subduction (e.g., the western Mediterranean region) or lithospheric underthrusting (as proposed in western Tibet). Over the last decade, improved geochronological constraints on the timing of ore formation and key tectonic events have revealed that many porphyry deposits that were previously assumed to be subduction-related are in fact broadly collision-related, some forming in back-arc settings in advance of collision, some during collision, and others during post-collisional processes such as orogenic collapse and/or delamination of subcontinental mantle lithosphere. While the formation of subduction-related porphyries is quite well understood, collisional metallogeny is more complex, and may involve a number of different processes or sources. These include melting of: orogenically thickened crust; previously subduction-modified lithosphere (including metasomatized mantle, underplated mafic rocks, or lower crustal arc plutons and cumulates); or upwelling asthenosphere (e.g., in response to delamination, slab breakoff, back-arc extension, or orogenic collapse). The most fertile sources for syn- and post-collisional porphyry deposits appear to be subduction-modified lithosphere, because these hydrated lithologies melt at relatively low temperatures during later tectonomagmatic events, and retain the oxidized and relatively metalliferous character of the original arc magmatism. Unusually metallically enriched lithospheric sources do not seem to be required, but the amount of residual sulfide phases in these rocks may control metal ratios (e.g., Cu:Au) in subsequent magmatic hydrothermal ore deposits. Relatively Au-rich deposits potentially form in these settings, as observed in the Carpathians (e.g., Roşia Montană), Turkey (Kisladag, Çöpler), and Iran (Sari Gunay, Dalli), although the majority of syn- and post-collisional porphyries are Cu–Mo-rich, and resemble normal subduction-related deposits (e.g., in the Gangdese belt of southern Tibet). This similarity extends to the associated igneous rocks, which, being derived from subduction-modified sources, largely retain the geochemical and isotopic character of those original arc magmas. While still retaining a broadly calc-alkaline character, these rocks may extend to mildly alkaline (shoshonitic) compositions, and may display adakite-like trace element signatures (high Sr/Y and La/Yb ratios) reflecting melting of deep crustal garnet amphibolitic sources. But they are otherwise hard to distinguish from normal subduction-related magmas. Small, post-collisional mafic, alkaline volcanic centers are common throughout the orogen, but for the most part appear to be barren. However, similar rocks in other post-subduction settings around the world are associated with important alkalic-type porphyry and epithermal Au ± Cu deposits, and the potential for discovery of such deposits in the Tethyan orogen should not be overlooked.",
    url = "https://doi.org/10.1016/j.oregeorev.2014.11.009",
    doi = "10.1016/j.oregeorev.2014.11.009",
    openalex = "W2078221258",
    references = "doi101016jgr201207001, doi101016jjseaes201003008, doi1010291999tc900042"
}

Abstract. Tectonic reconstructions of Southeast Asia have given rise to numerous controversies that include the accretionary history of Sundaland and the enigmatic tectonic origin of the proto-South China Sea. We assimilate a diversity of geological and geophysical observations into a new regional plate model, coupled to a global model, to address these debates. Our approach takes into account terrane suturing and accretion histories, the location of subducted slabs imaged in mantle tomography in order to constrain the evolution of regional subduction zones, as well as plausible absolute and relative plate velocities and tectonic driving mechanisms. We propose a scenario of rifting from northern Gondwana in the latest Jurassic, driven by northward slab pull from north-dipping subduction of Tethyan crust beneath Eurasia, to detach East Java, Mangkalihat, southeast Borneo and West Sulawesi blocks that collided with a Tethyan intra-oceanic subduction zone in the mid-Cretaceous and subsequently accreted to the Sunda margin (i.e., southwest Borneo core) in the Late Cretaceous. In accounting for the evolution of plate boundaries, we propose that the Philippine Sea plate originated on the periphery of Tethyan crust forming this northward conveyor. We implement a revised model for the Tethyan intra-oceanic subduction zones to reconcile convergence rates, changes in volcanism and the obduction of ophiolites. In our model the northward margin of Greater India collides with the Kohistan–Ladakh intra-oceanic arc at ∼53 Ma, followed by continent–continent collision closing the Shyok and Indus–Tsangpo suture zones between ∼42 and 34 Ma. We also account for the back-arc opening of the proto-South China Sea from ∼65 Ma, consistent with extension along east Asia and the formation of supra-subduction zone ophiolites presently found on the island of Mindoro. The related rifting likely detached the Semitau continental fragment from South China, which accreted to northern Borneo in the mid-Eocene, to account for the Sarawak Orogeny. Rifting then re-initiated along southeast China by 37 Ma to open the South China Sea, resulting in the complete consumption of proto-South China Sea by ∼17 Ma when the collision of the Dangerous Grounds and northern Palawan blocks with northern Borneo choked the subduction zone to result in the Sabah Orogeny and the obduction of ophiolites in Palawan and Mindoro. We conclude that the counterclockwise rotation of Borneo was accommodated by oroclinal bending consistent with paleomagnetic constraints, the curved lithospheric lineaments observed in gravity anomalies of the Java Sea and the curvature of the Cretaceous Natuna paleo-subduction zone. We complete our model by constructing a time-dependent network of topological plate boundaries and gridded paleo-ages of oceanic basins, allowing us to compare our plate model evolution to seismic tomography. In particular, slabs observed at depths shallower than ∼1000 km beneath northern Borneo and the South China Sea are likely to be remnants of the proto-South China Sea basin.

@article{doi105194se52272014,
    author = "Zahirovic, Sabin and Seton, Maria and Müller, R. Dietmar",
    title = "The Cretaceous and Cenozoic tectonic evolution of Southeast Asia",
    year = "2014",
    journal = "Solid Earth",
    abstract = "Abstract. Tectonic reconstructions of Southeast Asia have given rise to numerous controversies that include the accretionary history of Sundaland and the enigmatic tectonic origin of the proto-South China Sea. We assimilate a diversity of geological and geophysical observations into a new regional plate model, coupled to a global model, to address these debates. Our approach takes into account terrane suturing and accretion histories, the location of subducted slabs imaged in mantle tomography in order to constrain the evolution of regional subduction zones, as well as plausible absolute and relative plate velocities and tectonic driving mechanisms. We propose a scenario of rifting from northern Gondwana in the latest Jurassic, driven by northward slab pull from north-dipping subduction of Tethyan crust beneath Eurasia, to detach East Java, Mangkalihat, southeast Borneo and West Sulawesi blocks that collided with a Tethyan intra-oceanic subduction zone in the mid-Cretaceous and subsequently accreted to the Sunda margin (i.e., southwest Borneo core) in the Late Cretaceous. In accounting for the evolution of plate boundaries, we propose that the Philippine Sea plate originated on the periphery of Tethyan crust forming this northward conveyor. We implement a revised model for the Tethyan intra-oceanic subduction zones to reconcile convergence rates, changes in volcanism and the obduction of ophiolites. In our model the northward margin of Greater India collides with the Kohistan–Ladakh intra-oceanic arc at ∼53 Ma, followed by continent–continent collision closing the Shyok and Indus–Tsangpo suture zones between ∼42 and 34 Ma. We also account for the back-arc opening of the proto-South China Sea from ∼65 Ma, consistent with extension along east Asia and the formation of supra-subduction zone ophiolites presently found on the island of Mindoro. The related rifting likely detached the Semitau continental fragment from South China, which accreted to northern Borneo in the mid-Eocene, to account for the Sarawak Orogeny. Rifting then re-initiated along southeast China by 37 Ma to open the South China Sea, resulting in the complete consumption of proto-South China Sea by ∼17 Ma when the collision of the Dangerous Grounds and northern Palawan blocks with northern Borneo choked the subduction zone to result in the Sabah Orogeny and the obduction of ophiolites in Palawan and Mindoro. We conclude that the counterclockwise rotation of Borneo was accommodated by oroclinal bending consistent with paleomagnetic constraints, the curved lithospheric lineaments observed in gravity anomalies of the Java Sea and the curvature of the Cretaceous Natuna paleo-subduction zone. We complete our model by constructing a time-dependent network of topological plate boundaries and gridded paleo-ages of oceanic basins, allowing us to compare our plate model evolution to seismic tomography. In particular, slabs observed at depths shallower than ∼1000 km beneath northern Borneo and the South China Sea are likely to be remnants of the proto-South China Sea basin.",
    url = "https://doi.org/10.5194/se-5-227-2014",
    doi = "10.5194/se-5-227-2014",
    openalex = "W2004974805",
    references = "doi1010160012821x85901657, doi1010160025322795001379, doi101016jearscirev200801007, doi101016jpalaeo200606041, doi101046j13652117200300215x"
}

@incollection{keppie2014western,
    author = "Keppie, D. Fraser",
    title = "Western Caribbean Tectonics",
    year = "2014",
    booktitle = "SpringerBriefs in Earth Sciences",
    url = "https://doi.org/10.1007/978-1-4614-9616-8\_2",
    doi = "10.1007/978-1-4614-9616-8\_2",
    openalex = "W187056137",
    pages = "11-60",
    references = "doi101016jearscirev201203002, doi101017cbo9780511807442, doi1010292005rg000183, doi1010292007gc001743, doi101029gm100, doi101029jb073i006p01959, doi101038359123a0, doi101111j1365246x200904491x, doi101111j174754572003tb00036x, doi107208chicago97802262172390010001, openalexw2788326797"
}

@article{sakai2017tectonics,
    author = "Sakai, Harutaka and Imayama, Takeshi and Yoshida, Kohki and Asahi, Katsuhiko",
    title = "Tectonics of the Himalayas",
    year = "2017",
    journal = "The Journal of the Geological Society of Japan",
    url = "https://doi.org/10.5575/geosoc.2017.0026",
    doi = "10.5575/geosoc.2017.0026",
    number = "6",
    openalex = "W2737233288",
    pages = "403-421",
    volume = "123",
    references = "doi101016s0012821x96002014, doi1010291999jb900292, doi1010292001jb000359, doi1010292006jb004706, doi101029jb075i014p02625, doi101038366557a0, doi101038386061a0, doi101126science27452931684, doi1023071794401, doi102475ajs27511"
}

@incollection{roy2018himalayas,
    author = "Roy, A.B. and Purohit, Ritesh",
    title = "Himalayas: Postcollision Evolutionary Tectonics",
    year = "2018",
    booktitle = "Indian Shield",
    url = "https://doi.org/10.1016/b978-0-12-809839-4.00019-9",
    doi = "10.1016/b978-0-12-809839-4.00019-9",
    openalex = "W2799469229",
    pages = "329-337",
    references = "doi1010160031018283900123, doi101016s0743954798000026, doi1010291999jb900405, doi1010292005jb004120, doi101038379505a0, doi101111j15251314200400522x, doi1011301052517320010110004ehgatg20co2, doi101130g197301, doi101130ges006061, doi101146annurevearth281211"
}

The Himalayan-Tibetan orogen culminated during the Cenozoic India -- Asia collision, but its geological framework and initial growth were fundamentally the result of multiple, previous ocean closure and intercontinental suturing events. As such, the Himalayan-Tibetan orogen provides an ideal laboratory to investigate geological signatures of the suturing process in general, and how the Earth9s highest and largest orogenic feature formed in specific. This paper synthesizes the Triassic through Cenozoic geology of the central Himalayan-Tibetan orogen and presents our tectonic interpretations in a time series of schematic lithosphere-scale cross-sections and paleogeographic maps. We suggest that north-dipping subducting slabs beneath Asian continental terranes associated with closure of the Paleo-, Meso-, and Neo-Tethys oceans experienced phases of southward trench retreat prior to intercontinental suturing. These trench retreat events created ophiolites in forearc extensional settings and/or a backarc oceanic basins between rifted segments of upper-plate continental margin arcs. This process may have occurred at least three times along the southern Asian margin during northward subduction of Neo-Tethys oceanic lithosphere: from ∼174 to 156 Ma; 132 to 120 Ma; and 90 to 70 Ma. At most other times, the Tibetan terranes underwent Cordilleran-style or collisional contractional deformation. Geological records indicate that most of northern and central Tibet (the Hoh-Xil and Qiangtang terranes, respectively) were uplifted above sea level by Jurassic time, and southern Tibet (the Lhasa terrane) north of its forearc region has been above sea level since ∼100 Ma. Stratigraphic evidence indicates that the northern Himalayan margin of India collided with an Asian-affinity subduction complex -- forearc -- arc system beginning at ∼60 Ma. Both the Himalaya (composed of Indian crust) and Tibet show continuous geological records of orogenesis since ∼60 Ma. As no evidence exists in the rock record for a younger suture, the simplest interpretation of the geology is that India -- Asia collision initiated at ∼60 Ma. Plate circuit, paleomagnetic, and structural reconstructions, however, suggest that the southern margin of Asia was too far north of India to have collided with it at that time. Seismic tomographic images are also suggestive of a second, more southerly Neo-Tethyan oceanic slab in the lower mantle where the northernmost margin of India may have been located at ∼60 Ma. The geology of Tibet and the India -- Asia suture zone permits an alternative collision scenario in which the continental margin arc along southern Asia (the Gangdese arc) was split by extension beginning at ∼90 Ma, and along with its forearc to the south (the Xigaze forearc), rifted southward and opened a backarc ocean basin. The rifted arc collided with India at ∼60 Ma whereas the hypothetical backarc ocean basin may not have been consumed until ∼45 Ma. A compilation of igneous age data from Tibet shows that the most recent phase of Gangdese arc magmatism in the southern Lhasa terrane initiated at ∼70 Ma, peaked at ∼51 Ma, and terminated at ∼38 Ma. Cenozoic potassic-adakitic magmatism initiated at ∼45 Ma within a ∼200-km-wide elliptical area within the northern Qiangtang terrane, after which it swept westward and southward with time across central Tibet until ∼26 Ma. At 26 to 23 Ma, potassic-adakitic magmatism swept southward across the Lhasa terrane, a narrow (∼20 km width), orogen-parallel basin developed at low elevation along the axis of the India -- Asia suture zone (the Kailas basin), and Greater Himalayan Sequence rocks began extruding southward between the South Tibetan Detachment and Main Central Thrust. The Kailas basin was then uplifted to \>4 km elevation by ∼20 Ma, after which parts of the India -- Asia suture zone and Gangdese arc experienced \>6 km of exhumation (between ∼20 and 16 Ma). Between ∼16 and 12 Ma, slip along the South Tibetan Detachment terminated and east-west extension initiated in the northern Himalaya and Tibet. Potassic-adakitic magmatism in the Lhasa terrane shows a northward younging trend in the age of its termination, beginning at 20 to 18 Ma until volcanism ended at 8 Ma. We interpret the post-45 Ma geological evolution in the context of the subduction dynamics of Indian continental lithosphere and its interplay with delamination of Asian mantle lithosphere.

@article{doi10247503201901,
    author = "Kapp, Paul and DeCelles, Peter G.",
    title = "Mesozoic–Cenozoic geological evolution of the Himalayan-Tibetan orogen and working tectonic hypotheses",
    year = "2019",
    journal = "American Journal of Science",
    abstract = "The Himalayan-Tibetan orogen culminated during the Cenozoic India -- Asia collision, but its geological framework and initial growth were fundamentally the result of multiple, previous ocean closure and intercontinental suturing events. As such, the Himalayan-Tibetan orogen provides an ideal laboratory to investigate geological signatures of the suturing process in general, and how the Earth9s highest and largest orogenic feature formed in specific. This paper synthesizes the Triassic through Cenozoic geology of the central Himalayan-Tibetan orogen and presents our tectonic interpretations in a time series of schematic lithosphere-scale cross-sections and paleogeographic maps. We suggest that north-dipping subducting slabs beneath Asian continental terranes associated with closure of the Paleo-, Meso-, and Neo-Tethys oceans experienced phases of southward trench retreat prior to intercontinental suturing. These trench retreat events created ophiolites in forearc extensional settings and/or a backarc oceanic basins between rifted segments of upper-plate continental margin arcs. This process may have occurred at least three times along the southern Asian margin during northward subduction of Neo-Tethys oceanic lithosphere: from ∼174 to 156 Ma; 132 to 120 Ma; and 90 to 70 Ma. At most other times, the Tibetan terranes underwent Cordilleran-style or collisional contractional deformation. Geological records indicate that most of northern and central Tibet (the Hoh-Xil and Qiangtang terranes, respectively) were uplifted above sea level by Jurassic time, and southern Tibet (the Lhasa terrane) north of its forearc region has been above sea level since ∼100 Ma. Stratigraphic evidence indicates that the northern Himalayan margin of India collided with an Asian-affinity subduction complex -- forearc -- arc system beginning at ∼60 Ma. Both the Himalaya (composed of Indian crust) and Tibet show continuous geological records of orogenesis since ∼60 Ma. As no evidence exists in the rock record for a younger suture, the simplest interpretation of the geology is that India -- Asia collision initiated at ∼60 Ma. Plate circuit, paleomagnetic, and structural reconstructions, however, suggest that the southern margin of Asia was too far north of India to have collided with it at that time. Seismic tomographic images are also suggestive of a second, more southerly Neo-Tethyan oceanic slab in the lower mantle where the northernmost margin of India may have been located at ∼60 Ma. The geology of Tibet and the India -- Asia suture zone permits an alternative collision scenario in which the continental margin arc along southern Asia (the Gangdese arc) was split by extension beginning at ∼90 Ma, and along with its forearc to the south (the Xigaze forearc), rifted southward and opened a backarc ocean basin. The rifted arc collided with India at ∼60 Ma whereas the hypothetical backarc ocean basin may not have been consumed until ∼45 Ma. A compilation of igneous age data from Tibet shows that the most recent phase of Gangdese arc magmatism in the southern Lhasa terrane initiated at ∼70 Ma, peaked at ∼51 Ma, and terminated at ∼38 Ma. Cenozoic potassic-adakitic magmatism initiated at ∼45 Ma within a ∼200-km-wide elliptical area within the northern Qiangtang terrane, after which it swept westward and southward with time across central Tibet until ∼26 Ma. At 26 to 23 Ma, potassic-adakitic magmatism swept southward across the Lhasa terrane, a narrow (∼20 km width), orogen-parallel basin developed at low elevation along the axis of the India -- Asia suture zone (the Kailas basin), and Greater Himalayan Sequence rocks began extruding southward between the South Tibetan Detachment and Main Central Thrust. The Kailas basin was then uplifted to \>4 km elevation by ∼20 Ma, after which parts of the India -- Asia suture zone and Gangdese arc experienced \>6 km of exhumation (between ∼20 and 16 Ma). Between ∼16 and 12 Ma, slip along the South Tibetan Detachment terminated and east-west extension initiated in the northern Himalaya and Tibet. Potassic-adakitic magmatism in the Lhasa terrane shows a northward younging trend in the age of its termination, beginning at 20 to 18 Ma until volcanism ended at 8 Ma. We interpret the post-45 Ma geological evolution in the context of the subduction dynamics of Indian continental lithosphere and its interplay with delamination of Asian mantle lithosphere.",
    url = "https://doi.org/10.2475/03.2019.01",
    doi = "10.2475/03.2019.01",
    openalex = "W2946391716",
    references = "doi1010022014tc003522, doi101002tect20057, doi101007s0019000600303, doi101016jearscirev201206007, doi101016jepsl200408019, doi101016jepsl201301023, doi101016jepsl201609003, doi101016jepsl201710041, doi101016jgr201207001, doi101016jjseaes201003008, doi101016jjseaes201409012, doi101016s0012821x99001314, doi101016s0012821x99002770, doi101016s0743954798000026, doi1010292010jb007673, doi1010292011tc002868, doi101029tc007i006p01123, doi101038332695a0, doi101038373055a0, doi101038414738a, doi101038ngeo1669, doi101073pnas1117262109, doi101130b253881, doi101130spe269, openalexw614437925"
}

Thermochronology can reconstruct the thermal history of a rock based on thermally resetting radiometric age, which is useful for estimating a regional exhumation history when applied to rocks exhumed from a great depth. In particular, systems having lower closure temperatures are called “low-temperature thermochronology” and have been used to study tectonics in the shallow crust. In this paper, low-temperature thermochronology and its application to tectonics in the shallow crust are comprehensively reviewed, focusing particularly on the uplift and exhumation histories of mountainous regions. This review paper comprises two parts. In the first part, fundamentals of low-temperature thermochronology are reviewed, including some representative thermochronometers, mathematical descriptions of thermal annealing/diffusion, concepts of closure temperature and partial annealing/retention zone, and inversion method for computing thermal history on the basis of thermochronologic data. In the second part, application to mountain formation is described, including terminology of uplift and exhumation, methodology for estimating cooling and exhumation history based on cooling ages, and some representative case studies around the world.

@article{doi105026jgeography128707,
    author = "Sueoka, Shigeru and Tagami, Takahiro",
    title = "Low-temperature Thermochronology and Its Application to Tectonics in the Shallow Crust",
    year = "2019",
    journal = "Journal of Geography (Chigaku Zasshi)",
    abstract = "Thermochronology can reconstruct the thermal history of a rock based on thermally resetting radiometric age, which is useful for estimating a regional exhumation history when applied to rocks exhumed from a great depth. In particular, systems having lower closure temperatures are called “low-temperature thermochronology” and have been used to study tectonics in the shallow crust. In this paper, low-temperature thermochronology and its application to tectonics in the shallow crust are comprehensively reviewed, focusing particularly on the uplift and exhumation histories of mountainous regions. This review paper comprises two parts. In the first part, fundamentals of low-temperature thermochronology are reviewed, including some representative thermochronometers, mathematical descriptions of thermal annealing/diffusion, concepts of closure temperature and partial annealing/retention zone, and inversion method for computing thermal history on the basis of thermochronologic data. In the second part, application to mountain formation is described, including terminology of uplift and exhumation, methodology for estimating cooling and exhumation history based on cooling ages, and some representative case studies around the world.",
    url = "https://doi.org/10.5026/jgeography.128.707",
    doi = "10.5026/jgeography.128.707",
    openalex = "W2985685200",
    references = "sakai2017tectonics"
}

Abstract We process rigorously GPS data observed during the past 25 years from continental China to derive site secular velocities. Analysis of the velocity solution leads to the following results. (a) The deformation field inside the Tibetan plateau and Tien Shan is predominantly continuous, and large deformation gradients only exist perpendicular to the Indo‐Eurasian relative plate motion and are associated with a few large strike‐slip faults. (b) Lateral extrusions occur on both the east and west sides of the plateau. The westward extrusion peaks at ~6 mm/yr in the Pamir‐Hindu Kush region. A bell‐shaped eastward extrusion involves most of the plateau at a maximum rate of ~20 mm/yr between the Jiali and Ganzi‐Yushu faults, and the pattern is consistent with gravitational flow in southern and southeastern Tibet where the crust shows widespread dilatation at 10–20 nanostrain/yr. (c) The southeast borderland of Tibet rotates clockwise around the eastern Himalaya syntaxis, with sinistral and dextral shear motions along faults at the outer and inner flanks of the rotation terrane. The result suggests gravitational flow accomplished through rotation and translation of smaller subblocks in the upper crust. (d) Outside of the Tibetan plateau and Tien Shan, deformation field is block‐like. However, unnegligible internal deformation on the order of a couple of nanostrain/yr is found for all blocks. The North China block, under a unique tectonic loading environment, deforms and rotates at rates significantly higher than its northern and southern neighboring blocks, attesting its higher seismicity rate and earthquake hazard potential than its neighbors.

@article{doi1010292019jb018774,
    author = "Wang, Min and Shen, Zheng‐Kang",
    title = "Present‐Day Crustal Deformation of Continental China Derived From GPS and Its Tectonic Implications",
    year = "2020",
    journal = "Journal of Geophysical Research Solid Earth",
    abstract = "Abstract We process rigorously GPS data observed during the past 25 years from continental China to derive site secular velocities. Analysis of the velocity solution leads to the following results. (a) The deformation field inside the Tibetan plateau and Tien Shan is predominantly continuous, and large deformation gradients only exist perpendicular to the Indo‐Eurasian relative plate motion and are associated with a few large strike‐slip faults. (b) Lateral extrusions occur on both the east and west sides of the plateau. The westward extrusion peaks at \textasciitilde 6 mm/yr in the Pamir‐Hindu Kush region. A bell‐shaped eastward extrusion involves most of the plateau at a maximum rate of \textasciitilde 20 mm/yr between the Jiali and Ganzi‐Yushu faults, and the pattern is consistent with gravitational flow in southern and southeastern Tibet where the crust shows widespread dilatation at 10–20 nanostrain/yr. (c) The southeast borderland of Tibet rotates clockwise around the eastern Himalaya syntaxis, with sinistral and dextral shear motions along faults at the outer and inner flanks of the rotation terrane. The result suggests gravitational flow accomplished through rotation and translation of smaller subblocks in the upper crust. (d) Outside of the Tibetan plateau and Tien Shan, deformation field is block‐like. However, unnegligible internal deformation on the order of a couple of nanostrain/yr is found for all blocks. The North China block, under a unique tectonic loading environment, deforms and rotates at rates significantly higher than its northern and southern neighboring blocks, attesting its higher seismicity rate and earthquake hazard potential than its neighbors.",
    url = "https://doi.org/10.1029/2019jb018774",
    doi = "10.1029/2019jb018774",
    openalex = "W2999289209",
    references = "doi101002grl50288, doi101007s0019000600303, doi1010160012821x81901898, doi1010292001gc000252, doi1010292005gl025546, doi1010292011jb008930, doi101038386061a0, doi101126science2765313788"
}

An earthquake of magnitude (Mw) 4.3 occurring on April 6, 2024 near Sargodha (Mianwali NW Punjab, Pakistan) has been analyzed through waveform inversion to understand the subsurface geological structure. This shallow-depth (19 km) event represents a strike-slip faulting with a dextral sense of movement. Gravity data of the epicentral area depicts distinct anomalies representing two separate blocks showing an off-set in the same direction as determined by the seismic inversion validating modeling results. In our opinion, these structures represent second-order tectonics, potentially emerging as a response to the hindrance caused by the Sargodha High to southward movement of the Himalayan deformation front. Alternatively, R-shears associated with the western boundary of the Indian plate could provide another explanation for such strike-slip mechanism events. Crustal shortening along the deformation front is being accommodated through aseismic slip along a viscous décollement in the Salt Range and seismic slip within the brittle basement rocks of the Sargodha region as represented by the analyzed seismic event. This dual process plays a key role in shaping the tectonic features in study area. Detailed studies of small to moderate seismic events can help in delineating the subsurface seismogenic structures for development of better seismo-tectonic model for realistic seismic hazard assessment in the region.

@article{tahir2024basement,
    author = "Tahir, Mohammad and Saif, Bilal and Iqbal, Tahir and Habib, Raja Adnan and Iqbal, Talat and Shah, Muhammad Ali",
    title = "Basement Neo-Tectonics of Western Himalayas from Seismic and Gravity Data Perspective",
    year = "2024",
    journal = "Annals of Geophysics",
    abstract = "An earthquake of magnitude (Mw) 4.3 occurring on April 6, 2024 near Sargodha (Mianwali NW Punjab, Pakistan) has been analyzed through waveform inversion to understand the subsurface geological structure. This shallow-depth (19 km) event represents a strike-slip faulting with a dextral sense of movement. Gravity data of the epicentral area depicts distinct anomalies representing two separate blocks showing an off-set in the same direction as determined by the seismic inversion validating modeling results. In our opinion, these structures represent second-order tectonics, potentially emerging as a response to the hindrance caused by the Sargodha High to southward movement of the Himalayan deformation front. Alternatively, R-shears associated with the western boundary of the Indian plate could provide another explanation for such strike-slip mechanism events. Crustal shortening along the deformation front is being accommodated through aseismic slip along a viscous décollement in the Salt Range and seismic slip within the brittle basement rocks of the Sargodha region as represented by the analyzed seismic event. This dual process plays a key role in shaping the tectonic features in study area. Detailed studies of small to moderate seismic events can help in delineating the subsurface seismogenic structures for development of better seismo-tectonic model for realistic seismic hazard assessment in the region.",
    url = "https://doi.org/10.4401/ag-9120",
    doi = "10.4401/ag-9120",
    number = "5",
    openalex = "W4404966550",
    pages = "S551",
    volume = "67"
}