Continental margins

@misc{veatch1939atlantic2,
    author = "Veatch, A. C. and Smith, P. A",
    title = "Atlantic submarine valleys of the United States and the Congo submarine valley",
    year = "1939",
    howpublished = "Geological Society of America, Special Paper, v. 7; 101 pp",
    note = "talkorigins\_source = {true}; raw\_reference = {Veatch, A. C., and Smith, P. A., 1939, Atlantic submarine valleys of the United States and the Congo submarine valley: Geological Society of America, Special Paper, v. 7; 101 pp.}"
}

The thermal history of Atlantic continental margins resembles that of the oceanic crust as it spreads away from a mid-oceanic ridge, since the margin was formed when a ridge began spreading beneath a pre-existing continent. During break-up the thickness of the continental crust along the new margin was reduced by subarea1 erosion and subcrustal processes. Afterwards the continental shelf subsided, probably due to thermal contraction of the lithosphere. The observed subsidence rate on the Atlantic and Gulf coasts of the United States declined exponentially with a time constant of about 50My, as it does for ridges. Except for the Florida peninsula, deviations of the observed sedimentation from a smooth curve with respect to time could be associated with eustatic changes and variations in the supply of sediments. The subsidence rate of basins in the mid-continent of North America also decreases with a 50 My time constant. In Kansas a subcrustal process must have thinned the crust and initiated subsidence as a sequence of thinly bedded sediments beneath the basin is uneroded.

@article{doi101111j1365246x1971tb02182x,
    author = "Sleep, Norman H.",
    title = "Thermal Effects of the Formation of Atlantic Continental Margins by Continental Break up",
    year = "1971",
    journal = "Geophysical Journal International",
    abstract = "The thermal history of Atlantic continental margins resembles that of the oceanic crust as it spreads away from a mid-oceanic ridge, since the margin was formed when a ridge began spreading beneath a pre-existing continent. During break-up the thickness of the continental crust along the new margin was reduced by subarea1 erosion and subcrustal processes. Afterwards the continental shelf subsided, probably due to thermal contraction of the lithosphere. The observed subsidence rate on the Atlantic and Gulf coasts of the United States declined exponentially with a time constant of about 50My, as it does for ridges. Except for the Florida peninsula, deviations of the observed sedimentation from a smooth curve with respect to time could be associated with eustatic changes and variations in the supply of sediments. The subsidence rate of basins in the mid-continent of North America also decreases with a 50 My time constant. In Kansas a subcrustal process must have thinned the crust and initiated subsidence as a sequence of thinly bedded sediments beneath the basin is uneroded.",
    url = "https://doi.org/10.1111/j.1365-246x.1971.tb02182.x",
    doi = "10.1111/j.1365-246x.1971.tb02182.x",
    openalex = "W2140210515"
}

@book{crossref1974the,
    title = "The Geology of Continental Margins",
    year = "1974",
    url = "https://doi.org/10.1007/978-3-662-01141-6",
    doi = "10.1007/978-3-662-01141-6",
    openalex = "W2097058721",
    references = "doi101016s031554638771058x, doi101038181669b0, openalexw2989358995"
}

@incollection{heezen1974atlantictype,
    author = "Heezen, Bruce C.",
    title = "Atlantic-Type Continental Margins",
    year = "1974",
    booktitle = "The Geology of Continental Margins",
    url = "https://doi.org/10.1007/978-3-662-01141-6\_2",
    doi = "10.1007/978-3-662-01141-6\_2",
    openalex = "W205748577",
    pages = "13-24",
    references = "doi101016002532276490012x, doi1010160025322768900078, doi1010160079194659900059, doi101038220470a0, doi101086627414, doi101126science1503697709, doi101126science1523721502, doi10113000167606196172193adsc20co2, doi101130spe65p1, doi1013065d25c97d16c111d78645000102c1865d"
}

@article{moore1976the,
    author = "MOORE, GEORGE T.",
    title = "The Geology of Continental Margins",
    year = "1976",
    journal = "Soil Science",
    url = "https://doi.org/10.1097/00010694-197606000-00010",
    doi = "10.1097/00010694-197606000-00010",
    number = "6",
    openalex = "W1971868031",
    pages = "374",
    volume = "121"
}

@misc{curray1977geology,
    author = "Curray, Joseph R. and Dickinson, William R. and Dow, Wallace G. and Emery, Kenneth O. and Seely, Donald R. and Vail, Peter R. and Yarborough, Hunter",
    title = "Geology of Continental Margins",
    year = "1977",
    url = "https://doi.org/10.1306/ce5387",
    doi = "10.1306/ce5387",
    openalex = "W2460971277"
}

@article{doi1010160012821x78900365,
    author = "Steckler, M. S. and Watts, A. B.",
    title = "Subsidence of the Atlantic-type continental margin off New York",
    year = "1978",
    journal = "Earth and Planetary Science Letters",
    url = "https://doi.org/10.1016/0012-821x(78)90036-5",
    doi = "10.1016/0012-821x(78)90036-5",
    openalex = "W2133562679",
    references = "doi1010160012821x78900717, doi10113000167606195970291smitao20co2"
}

The distribution of intraplate earthquakes and of igneous rocks postdating continental rifting is summarized and placed into a plate tectonic framework for the following continental areas: eastern and central North America, Africa, Australia, Brazil, Greenland, Antarctica, Norway, Spitsbergen, India, and the margins of the Red Sea and Gulf of Aden. In continents, intraplate earthquakes tend to be concentrated along preexisting zones of weakness within areas affected by the youngest major orogenesis that predates the opening of the present oceans. Many preexisting zones of weakness (including fault zones, suture zones, failed rifts, and other tectonic boundaries), particularly those near continental margins, were reactivated during the early stages of continental separation. In contrast, intraplate shocks rarely occur within the older oceanic lithosphere or within the interiors of ancient cratonic blocks of the continents. In several continental areas, rocks and tectonic features postdating the opening of present‐day oceans, including carbonatites, kimberlites, other alkalic rocks, mafic dikes, and ring dikes, as well as some of the largest intraplate shocks, seem to be located preferentially along old zones of weakness near the ends of major oceanic transform faults that were active in the early opening of adjacent oceans. In several places, alkaline magmatism and earthquakes extend several hundred kilometers inland from the ends of oceanic transform faults (but not necessarily with the same strike as the transform fault). Major preexisting zones of weakness that are oriented subparallel to the directions of relative continental separation appear to control the locations of transform faults that develop in a new ocean. In some instances, alkaline magmatism persisted along reactivated features of this type for as long as 100 m.y. after the initial stages of continental fragmentation. Most kimberlites in South Africa seem to have been emplaced along preexisting zones of weakness that were reactivated during the early opening of the South Atlantic. The type of intraplate magmatism appears to be related to the thickness of the lithosphere. Unlike oceanic transform faults where large horizontal movements have occurred, reactivated zones of weakness in continents usually appear to have been the sites of only relatively small displacement. Seismic activity and alkaline magmatism may be controlled by deep fractures that penetrated the entire lithosphere to tap asthenospheric sources of magma. Seismic activity along these zones seems to occur in response to the present‐day stress regime, which is not necessarily the same as that which was active during the emplacement of the alkaline rocks. Other intraplate shocks are concentrated along old zones of weakness that are subparallel to continental margins. Such shocks are found in the Appalachians, northeastern and northern Greenland, Norway, Great Britain, Spitsbergen, northern Canada, and Australia. These zones of weakness were also reactivated during continental separation in either the Mesozoic or the Cenozoic. Evidence is now mounting for Cretaceous and Cenozoic deformation along some of these features. Although not many focal mechanism solutions or in situ measurements of stress are available for intraplate areas, horizontal compressive stresses appear to be present today in many of the pre‐Mesozoic orogenic belts that were reactivated by continental rifting. This evidence, as well as examples of Cenozoic thrust faulting, indicates that the stress field has changed since rifting commenced. High compressive stresses, the absence of earthquakes in Antarctica, their near absence along the margins of the Gulf of Mexico, and the much lower levels of activity in the oceanic lithosphere adjacent to most continents argue against mere sedimentary loading and the cooling of the oceanic lithosphere as the main source of stress that is reactivating faults of these older fold belts. The large compressive stresses and the uplift found in many continental areas adjacent to continental margins may be caused by a deep‐seated source in the mantle of long wavelength or by stresses transmitted in the lithosphere. These effects may be related to either the cooling and underplating of the continental lithosphere adjacent to continental margins, large tractions on the base of the lithosphere in shield areas, stress concentrations related to marked changes in the age and thickness of the lithosphere, convective motions of the mantle beneath these areas, or those regions acting like broad zones of weakness that are being compressed between adjacent areas of greater strength. During the fragmentation of a supercontinent, multibranched rifting usually follows the youngest zone of previous orogenesis and as much as possible avoids passing through old cratonic areas where the lithosphere is thick, cold, and strong. Rift junctions seem to be related to the preexisting mosaic of cratons and younger belts of deformation rather than to a motive force involving mantle plumes. Likewise, many zones of unusually high magmatic activity, i.e., hot spots, appear to be related to nodes or junctions in this mosaic pattern. Thus these hot spots appear to be passive features rather than the surficial expression of mantle plumes. Major transform faults that are active during the early opening of an ocean also tend to develop where the margins of the older cratons undergo an abrupt change in strike. During the early development of an ocean the preexisting mosaic of structural elements within the thick continental lithosphere may result in large normal forces across some plate margins, leaky transform faulting, and localized stress concentrations. The early directions of sea floor spreading and of transforming faulting may be altered by these boundary forces and by the geometrical constraints imposed in separating old cratonic blocks. These constraints are relaxed once old, thick lithosphere is no longer in contact across long transform faults. Since these early directions are strongly influenced by the preexisting tectonic framework and may not coincide with the direction of the forces driving the plates apart, early transform faults may have components of extension (or compression) along them in addition to strike slip motion. A small component of extension may be responsible for the formation of volcanic ridges and seamount chains such as the Walvis ridge, Rio Grande rise, and New England seamount chain. These features predate the marked change in the strike of transform faulting that occurred in the North and South Atlantic about 80 m.y. ago as thin oceanic lithosphere finally came in contact across large oceanic transform faults. Several zones of intraplate magmatism in the surrounding continents also ceased at that time.

@article{doi101029rg016i004p00621,
    author = "Sykes, Lynn R.",
    title = "Intraplate seismicity, reactivation of preexisting zones of weakness, alkaline magmatism, and other tectonism postdating continental fragmentation",
    year = "1978",
    journal = "Reviews of Geophysics",
    abstract = "The distribution of intraplate earthquakes and of igneous rocks postdating continental rifting is summarized and placed into a plate tectonic framework for the following continental areas: eastern and central North America, Africa, Australia, Brazil, Greenland, Antarctica, Norway, Spitsbergen, India, and the margins of the Red Sea and Gulf of Aden. In continents, intraplate earthquakes tend to be concentrated along preexisting zones of weakness within areas affected by the youngest major orogenesis that predates the opening of the present oceans. Many preexisting zones of weakness (including fault zones, suture zones, failed rifts, and other tectonic boundaries), particularly those near continental margins, were reactivated during the early stages of continental separation. In contrast, intraplate shocks rarely occur within the older oceanic lithosphere or within the interiors of ancient cratonic blocks of the continents. In several continental areas, rocks and tectonic features postdating the opening of present‐day oceans, including carbonatites, kimberlites, other alkalic rocks, mafic dikes, and ring dikes, as well as some of the largest intraplate shocks, seem to be located preferentially along old zones of weakness near the ends of major oceanic transform faults that were active in the early opening of adjacent oceans. In several places, alkaline magmatism and earthquakes extend several hundred kilometers inland from the ends of oceanic transform faults (but not necessarily with the same strike as the transform fault). Major preexisting zones of weakness that are oriented subparallel to the directions of relative continental separation appear to control the locations of transform faults that develop in a new ocean. In some instances, alkaline magmatism persisted along reactivated features of this type for as long as 100 m.y. after the initial stages of continental fragmentation. Most kimberlites in South Africa seem to have been emplaced along preexisting zones of weakness that were reactivated during the early opening of the South Atlantic. The type of intraplate magmatism appears to be related to the thickness of the lithosphere. Unlike oceanic transform faults where large horizontal movements have occurred, reactivated zones of weakness in continents usually appear to have been the sites of only relatively small displacement. Seismic activity and alkaline magmatism may be controlled by deep fractures that penetrated the entire lithosphere to tap asthenospheric sources of magma. Seismic activity along these zones seems to occur in response to the present‐day stress regime, which is not necessarily the same as that which was active during the emplacement of the alkaline rocks. Other intraplate shocks are concentrated along old zones of weakness that are subparallel to continental margins. Such shocks are found in the Appalachians, northeastern and northern Greenland, Norway, Great Britain, Spitsbergen, northern Canada, and Australia. These zones of weakness were also reactivated during continental separation in either the Mesozoic or the Cenozoic. Evidence is now mounting for Cretaceous and Cenozoic deformation along some of these features. Although not many focal mechanism solutions or in situ measurements of stress are available for intraplate areas, horizontal compressive stresses appear to be present today in many of the pre‐Mesozoic orogenic belts that were reactivated by continental rifting. This evidence, as well as examples of Cenozoic thrust faulting, indicates that the stress field has changed since rifting commenced. High compressive stresses, the absence of earthquakes in Antarctica, their near absence along the margins of the Gulf of Mexico, and the much lower levels of activity in the oceanic lithosphere adjacent to most continents argue against mere sedimentary loading and the cooling of the oceanic lithosphere as the main source of stress that is reactivating faults of these older fold belts. The large compressive stresses and the uplift found in many continental areas adjacent to continental margins may be caused by a deep‐seated source in the mantle of long wavelength or by stresses transmitted in the lithosphere. These effects may be related to either the cooling and underplating of the continental lithosphere adjacent to continental margins, large tractions on the base of the lithosphere in shield areas, stress concentrations related to marked changes in the age and thickness of the lithosphere, convective motions of the mantle beneath these areas, or those regions acting like broad zones of weakness that are being compressed between adjacent areas of greater strength. During the fragmentation of a supercontinent, multibranched rifting usually follows the youngest zone of previous orogenesis and as much as possible avoids passing through old cratonic areas where the lithosphere is thick, cold, and strong. Rift junctions seem to be related to the preexisting mosaic of cratons and younger belts of deformation rather than to a motive force involving mantle plumes. Likewise, many zones of unusually high magmatic activity, i.e., hot spots, appear to be related to nodes or junctions in this mosaic pattern. Thus these hot spots appear to be passive features rather than the surficial expression of mantle plumes. Major transform faults that are active during the early opening of an ocean also tend to develop where the margins of the older cratons undergo an abrupt change in strike. During the early development of an ocean the preexisting mosaic of structural elements within the thick continental lithosphere may result in large normal forces across some plate margins, leaky transform faulting, and localized stress concentrations. The early directions of sea floor spreading and of transforming faulting may be altered by these boundary forces and by the geometrical constraints imposed in separating old cratonic blocks. These constraints are relaxed once old, thick lithosphere is no longer in contact across long transform faults. Since these early directions are strongly influenced by the preexisting tectonic framework and may not coincide with the direction of the forces driving the plates apart, early transform faults may have components of extension (or compression) along them in addition to strike slip motion. A small component of extension may be responsible for the formation of volcanic ridges and seamount chains such as the Walvis ridge, Rio Grande rise, and New England seamount chain. These features predate the marked change in the strike of transform faulting that occurred in the North and South Atlantic about 80 m.y. ago as thin oceanic lithosphere finally came in contact across large oceanic transform faults. Several zones of intraplate magmatism in the surrounding continents also ceased at that time.",
    url = "https://doi.org/10.1029/rg016i004p00621",
    doi = "10.1029/rg016i004p00621",
    openalex = "W1983992782",
    references = "doi1010160040195168900590, doi101038207343a0, doi101038211676a0, doi101086627882, doi101111j1365246x1974tb00613x, doi101126science1894201419, doi10113000167606197283619ssitna20co2, doi101130001676061973843137ptateo20co2, doi1011300091761319742377ptmfte20co2, doi1023071796560, doi105408002213687121, openalexw630270902"
}

@misc{woodbury1978gulf3,
    author = "Woodbury, H. O. and Spotts, J. H. and Akers, W. H",
    title = "Gulf of Mexico continental-slope sediments and sedimentation, in, 7 of AAPG Studies in Geology",
    year = "1978",
    howpublished = "p. 117-137",
    note = "talkorigins\_source = {true}; raw\_reference = {Woodbury, H. O., Spotts, J. H., and Akers, W. H., 1978, Gulf of Mexico continental-slope sediments and sedimentation, in, 7 of AAPG Studies in Geology: p. 117-137.}"
}

Gravity and magnetic anomalies bordering the continental margins of the southern South Atlantic Ocean are compared, in detail, on conjugate sides of the ridge crest, and a model for the boundary between oceanic and continental basement is given. The area of study includes the predominantly sheared margins of the Agulhas‐Falkland fracture zone and the rifted margins of Argentina and southern Africa south of the Rio Grande Rise and Walvis Ridge, respectively. These margins have associated with them, for the most part, linear magnetic anomalies that can be modeled as edge effect anomalies separating oceanic from continental basement. Coincident with the magnetic anomalies are gradients in the isostatic gravity anomaly. We have taken the location of these geophysical lineaments on the African margin and rotated them clockwise to fit the anomalies on the Argentine margin. This fit, which gives us a new pole of total closing for the South Atlantic Ocean, obviates, for the most part, the gaps and overlaps observed in other reconstructions. The improved fit thereby suggests rigid plate behavior and minimum stretching of continental crust during the early opening of the southern South Atlantic Ocean. A zone of crustal stretching may be present in the southernmost Argentine and Cape basin margins. New poles of early opening for the South Atlantic Ocean have been determined (from 130 to 107 m.y. B.P. and from 107 to 80 m.y. B.P.) utilizing the above reconstruction as well as the strike of the Agulhas‐Falkland fracture zone where it is well determined. The earliest pole, which is located much farther south than previously determined early poles, satisfies not only the geophysical data in the southern regions but allows us to explain a number of outstanding problems north of the Rio Grande Rise‐Walvis Ridge area. These problems include the timing of the onset of sedimentation on the northern Brazil margin, the origin of the compressional features along the Venezuela margin, and the onset of open marine circulation between the North and South Atlantic oceans. Paleoreconstructions using the new early poles also align very well the seaward edge of the salt boundaries off Brazil and West Africa. The age of the salt, as inferred from the paleoreconstruction to its seaward boundaries, is younger than the age of magnetic anomaly M0. Furthermore, our paleoreconstructions show barriers for salt deposition not only across its southern termination (Walvis Ridge area) but also farther north in the equatorial regions. The salt, for the most part, has been deposited on oceanic crust. The new predrift reconstruction and early opening poles, taken together with the new identifications of the Mesozoic and Late Cenozoic sequences of magnetic anomalies, allow us to determine the magnitude and time interval of spreading center migration. In particular, we can demonstrate that ridge crest migrations of ∼1000 km have occurred along the strike of the Falkland escarpment. We demonstrate that the isostatic gravity gradient associated with the boundary between oceanic and continental basement is independent of the location of major sediment accumulations. We have modeled this anomaly as resulting from elevated oceanic basement adjacent to continental crust. This crustal model satisfies the limited upper crustal seismic data available near margins. The oceanic basement elevations are relics of a transient phenomenon associated with young rifted margins such as the East African and Red Sea rifts.

@article{doi101029jb084ib11p05973,
    author = "Rabinowitz, Philip D. and LaBrecque, John L.",
    title = "The Mesozoic South Atlantic Ocean and evolution of its continental margins",
    year = "1979",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "Gravity and magnetic anomalies bordering the continental margins of the southern South Atlantic Ocean are compared, in detail, on conjugate sides of the ridge crest, and a model for the boundary between oceanic and continental basement is given. The area of study includes the predominantly sheared margins of the Agulhas‐Falkland fracture zone and the rifted margins of Argentina and southern Africa south of the Rio Grande Rise and Walvis Ridge, respectively. These margins have associated with them, for the most part, linear magnetic anomalies that can be modeled as edge effect anomalies separating oceanic from continental basement. Coincident with the magnetic anomalies are gradients in the isostatic gravity anomaly. We have taken the location of these geophysical lineaments on the African margin and rotated them clockwise to fit the anomalies on the Argentine margin. This fit, which gives us a new pole of total closing for the South Atlantic Ocean, obviates, for the most part, the gaps and overlaps observed in other reconstructions. The improved fit thereby suggests rigid plate behavior and minimum stretching of continental crust during the early opening of the southern South Atlantic Ocean. A zone of crustal stretching may be present in the southernmost Argentine and Cape basin margins. New poles of early opening for the South Atlantic Ocean have been determined (from 130 to 107 m.y. B.P. and from 107 to 80 m.y. B.P.) utilizing the above reconstruction as well as the strike of the Agulhas‐Falkland fracture zone where it is well determined. The earliest pole, which is located much farther south than previously determined early poles, satisfies not only the geophysical data in the southern regions but allows us to explain a number of outstanding problems north of the Rio Grande Rise‐Walvis Ridge area. These problems include the timing of the onset of sedimentation on the northern Brazil margin, the origin of the compressional features along the Venezuela margin, and the onset of open marine circulation between the North and South Atlantic oceans. Paleoreconstructions using the new early poles also align very well the seaward edge of the salt boundaries off Brazil and West Africa. The age of the salt, as inferred from the paleoreconstruction to its seaward boundaries, is younger than the age of magnetic anomaly M0. Furthermore, our paleoreconstructions show barriers for salt deposition not only across its southern termination (Walvis Ridge area) but also farther north in the equatorial regions. The salt, for the most part, has been deposited on oceanic crust. The new predrift reconstruction and early opening poles, taken together with the new identifications of the Mesozoic and Late Cenozoic sequences of magnetic anomalies, allow us to determine the magnitude and time interval of spreading center migration. In particular, we can demonstrate that ridge crest migrations of ∼1000 km have occurred along the strike of the Falkland escarpment. We demonstrate that the isostatic gravity gradient associated with the boundary between oceanic and continental basement is independent of the location of major sediment accumulations. We have modeled this anomaly as resulting from elevated oceanic basement adjacent to continental crust. This crustal model satisfies the limited upper crustal seismic data available near margins. The oceanic basement elevations are relics of a transient phenomenon associated with young rifted margins such as the East African and Red Sea rifts.",
    url = "https://doi.org/10.1029/jb084ib11p05973",
    doi = "10.1029/jb084ib11p05973",
    openalex = "W2140538827",
    references = "doi1010070387307524111, doi101029jb073i012p03661, doi101029jb076i026p06294, doi101029jb076i032p07888, doi101098rsta19650020, doi101130001676061972833645wcomma20co2, doi10113000167606197283619ssitna20co2, doi1011300091761319775330rmptsf20co2, doi10130683d923ed16c711d78645000102c1865d, doi101785bssa0590010369"
}

In the northeast Atlantic, DSDP drilling results, combined with intensive geophysical surveys, permit a proposed model of the structural evolution of a starved, passive continental margin. Environment and tectonics of the rifting phase have been established. Active rifting took place in Early Cretaceous time in a pre-existing marine basin in contrast to many subaerial rift systems. The overall tectonic style is characterized by a series of tilted fault blocks bounded in many cases by listric faults. The rotation of the blocks (20-30) along listric faults reduced the thickness of the upper continental crust from 6 to 8 km to 4 to 5 km. Close to the near horizontal base of the listric faults, a strong horizontal reflector corresponding to the 6.3 to 4.9 km/s refraction interface has been interpreted as the boundary between the upper brittle and the lower ductile continental crusts. The Moho discontinuity, 25 km deep in the vicinity of the shelf break, is 12 km deep in the lower part of the margin. In this area the ductile part of the crust (6.3 km/s) is only 3 km thick.

@incollection{doi102973dsdpproc481541979,
    author = "Montadert, L. and Roberts, D.G. and de Charpal, O. and Guennoc, Pol",
    title = "Rifting and Subsidence of the Northern Continental Margin of the Bay of Biscay",
    year = "1979",
    booktitle = "U.S. Government Printing Office eBooks",
    abstract = "In the northeast Atlantic, DSDP drilling results, combined with intensive geophysical surveys, permit a proposed model of the structural evolution of a starved, passive continental margin. Environment and tectonics of the rifting phase have been established. Active rifting took place in Early Cretaceous time in a pre-existing marine basin in contrast to many subaerial rift systems. The overall tectonic style is characterized by a series of tilted fault blocks bounded in many cases by listric faults. The rotation of the blocks (20-30) along listric faults reduced the thickness of the upper continental crust from 6 to 8 km to 4 to 5 km. Close to the near horizontal base of the listric faults, a strong horizontal reflector corresponding to the 6.3 to 4.9 km/s refraction interface has been interpreted as the boundary between the upper brittle and the lower ductile continental crusts. The Moho discontinuity, 25 km deep in the vicinity of the shelf break, is 12 km deep in the lower part of the margin. In this area the ductile part of the crust (6.3 km/s) is only 3 km thick.",
    url = "https://doi.org/10.2973/dsdp.proc.48.154.1979",
    doi = "10.2973/dsdp.proc.48.154.1979",
    openalex = "W2485381019",
    references = "moore1976the"
}

@article{blot1982geology,
    author = "Blot, Claude",
    title = "Geology of the continental margins",
    year = "1982",
    journal = "Earth-Science Reviews",
    url = "https://doi.org/10.1016/0012-8252(82)90022-8",
    doi = "10.1016/0012-8252(82)90022-8",
    number = "1",
    openalex = "W1979318372",
    pages = "93",
    volume = "18"
}

@article{burke1982geology,
    author = "Burke, Kevin",
    title = "Geology of continental margins",
    year = "1982",
    journal = "Tectonophysics",
    url = "https://doi.org/10.1016/0040-1951(82)90169-x",
    doi = "10.1016/0040-1951(82)90169-x",
    number = "2-4",
    openalex = "W2921121073",
    pages = "364",
    volume = "84"
}

"Studies in Continental Margin Geology" contains papers from a research conference co-sponsored by AAPG and the University of Texas Institute for Geophysics held in Galveston, Texas in 1981. Rapid advances in the understanding of continental margin geology were taking place during the time period, based on major improvements in the quality and availability of regional seismic surveys plus other fields such as organic geochemistry. For the first time it was becoming common to have a visual characterization of tectonic processes at significant depths below the surface. Twenty-seven papers are presented that deal with field investigations of continental margin structure and stratigraphy. The geographic areas of study are global in nature and many of the descriptive results are derived from modern seismic investigations in areas where that type of data had not previously been available in commercial publications. Fifteen of the papers focus on rifted margins and the other twelve concern convergent margins. Twelve papers are model investigations of a variety of margin environmental processes, related to subjects such as depositional environments, biostratigraphy, organic matter deposition, and oil and gas occurrences as a function of the plate tectonic setting. An additional nine papers model the thermal and mechanical tectonic processes involved in the structural development along continental margins.

@incollection{doi101306m34430c9,
    author = "Naini, Bhoopal R. and Talwani, Manik",
    title = "Structural Framework and the Evolutionary History of the Continental Margin of Western India",
    year = "1982",
    booktitle = "American Association of Petroleum Geologists eBooks",
    abstract = {"Studies in Continental Margin Geology" contains papers from a research conference co-sponsored by AAPG and the University of Texas Institute for Geophysics held in Galveston, Texas in 1981. Rapid advances in the understanding of continental margin geology were taking place during the time period, based on major improvements in the quality and availability of regional seismic surveys plus other fields such as organic geochemistry. For the first time it was becoming common to have a visual characterization of tectonic processes at significant depths below the surface. Twenty-seven papers are presented that deal with field investigations of continental margin structure and stratigraphy. The geographic areas of study are global in nature and many of the descriptive results are derived from modern seismic investigations in areas where that type of data had not previously been available in commercial publications. Fifteen of the papers focus on rifted margins and the other twelve concern convergent margins. Twelve papers are model investigations of a variety of margin environmental processes, related to subjects such as depositional environments, biostratigraphy, organic matter deposition, and oil and gas occurrences as a function of the plate tectonic setting. An additional nine papers model the thermal and mechanical tectonic processes involved in the structural development along continental margins.},
    url = "https://doi.org/10.1306/m34430c9",
    doi = "10.1306/m34430c9",
    openalex = "W3112577813"
}

@article{doi1010160040195184901720,
    author = "Haworth, R. T. and Keen, C. and Williams, H.",
    title = "Transects of the ancient and modern continental margins of eastern Canada",
    year = "1984",
    journal = "Tectonophysics",
    url = "https://www.semanticscholar.org/paper/98435697d98d39056a30d2a62f18c23d1a036856",
    doi = "10.1016/0040-1951(84)90172-0",
    is_oa = "true",
    number = "1-2",
    pages = "93-94",
    semanticscholar_citation_count = "8",
    semanticscholar_id = "98435697d98d39056a30d2a62f18c23d1a036856",
    volume = "109"
}

When continents rift to form new ocean basins, the rifting is sometimes accompanied by massive igneous activity. We show that the production of magmatically active rifted margins and the effusion of flood basalts onto the adjacent continents can be explained by a simple model of rifting above a thermal anomaly in the underlying mantle. The igneous rocks are generated by decompression melting of hot asthenospheric mantle as it rises passively beneath the stretched and thinned lithosphere. Mantle plumes generate regions beneath the lithosphere typically 2000 km in diameter with temperatures raised 100–200°C above normal. These relatively small mantle temperature increases are sufficient to cause the generation of huge quantities of melt by decompression: an increase of 100°C above normal doubles the amount of melt whilst a 200°C increase can quadruple it. In the first part of this paper we develop our model to predict the effects of melt generation for varying amounts of stretching with a range of mantle temperatures. The melt generated by decompression migrates rapidly upward, until it is either extruded as basalt flows or intruded into or beneath the crust. Addition of large quantities of new igneous rock to the crust considerably modifies the subsidence in rifted regions. Stretching by a factor of 5 above normal temperature mantle produces immediate subsidence of more than 2 km in order to maintain isostatic equilibrium. If the mantle is 150°C or more hotter than normal, the same amount of stretching results in uplift above sea level. Melt generated from abnormally hot mantle is more magnesian rich than that produced from normal temperature mantle. This causes an increase in seismic velocity of the igneous rocks emplaced in the crust, from typically 6.8 km/s for normal mantle temperatures to 7.2 km/s or higher. There is a concomitant density increase. In the second part of the paper we review volcanic continental margins and flood basalt provinces globally and show that they are always related to the thermal anomaly created by a nearby mantle plume. Our model of melt generation in passively upwelling mantle beneath rifting continental lithosphere can explain all the major rift‐related igneous provinces. These include the Tertiary igneous provinces of Britain and Greenland and the associated volcanic continental margins caused by opening of the North Atlantic in the presence of the Iceland plume; the Paraná and parts of the Karoo flood basalts together with volcanic continental margins generated when the South Atlantic opened; the Deccan flood basalts of India and the Seychelles‐Saya da Malha volcanic province created when the Seychelles split off India above the Réunion hot spot; the Ethiopian and Yemen Traps created by rifting of the Red Sea and Gulf of Aden region above the Afar hot spot; and the oldest and probably originally the largest flood basalt province of the Karoo produced when Gondwana split apart. New continental splits do not always occur above thermal anomalies in the mantle caused by plumes, but when they do, huge quantities of igneous material are added to the continental crust. This is an important method of increasing the volume of the continental crust through geologic time.

@article{doi101029jb094ib06p07685,
    author = "White, R. S. and McKenzie, Dan",
    title = "Magmatism at rift zones: The generation of volcanic continental margins and flood basalts",
    year = "1989",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "When continents rift to form new ocean basins, the rifting is sometimes accompanied by massive igneous activity. We show that the production of magmatically active rifted margins and the effusion of flood basalts onto the adjacent continents can be explained by a simple model of rifting above a thermal anomaly in the underlying mantle. The igneous rocks are generated by decompression melting of hot asthenospheric mantle as it rises passively beneath the stretched and thinned lithosphere. Mantle plumes generate regions beneath the lithosphere typically 2000 km in diameter with temperatures raised 100–200°C above normal. These relatively small mantle temperature increases are sufficient to cause the generation of huge quantities of melt by decompression: an increase of 100°C above normal doubles the amount of melt whilst a 200°C increase can quadruple it. In the first part of this paper we develop our model to predict the effects of melt generation for varying amounts of stretching with a range of mantle temperatures. The melt generated by decompression migrates rapidly upward, until it is either extruded as basalt flows or intruded into or beneath the crust. Addition of large quantities of new igneous rock to the crust considerably modifies the subsidence in rifted regions. Stretching by a factor of 5 above normal temperature mantle produces immediate subsidence of more than 2 km in order to maintain isostatic equilibrium. If the mantle is 150°C or more hotter than normal, the same amount of stretching results in uplift above sea level. Melt generated from abnormally hot mantle is more magnesian rich than that produced from normal temperature mantle. This causes an increase in seismic velocity of the igneous rocks emplaced in the crust, from typically 6.8 km/s for normal mantle temperatures to 7.2 km/s or higher. There is a concomitant density increase. In the second part of the paper we review volcanic continental margins and flood basalt provinces globally and show that they are always related to the thermal anomaly created by a nearby mantle plume. Our model of melt generation in passively upwelling mantle beneath rifting continental lithosphere can explain all the major rift‐related igneous provinces. These include the Tertiary igneous provinces of Britain and Greenland and the associated volcanic continental margins caused by opening of the North Atlantic in the presence of the Iceland plume; the Paraná and parts of the Karoo flood basalts together with volcanic continental margins generated when the South Atlantic opened; the Deccan flood basalts of India and the Seychelles‐Saya da Malha volcanic province created when the Seychelles split off India above the Réunion hot spot; the Ethiopian and Yemen Traps created by rifting of the Red Sea and Gulf of Aden region above the Afar hot spot; and the oldest and probably originally the largest flood basalt province of the Karoo produced when Gondwana split apart. New continental splits do not always occur above thermal anomalies in the mantle caused by plumes, but when they do, huge quantities of igneous material are added to the continental crust. This is an important method of increasing the volume of the continental crust through geologic time.",
    url = "https://doi.org/10.1029/jb094ib06p07685",
    doi = "10.1029/jb094ib06p07685",
    openalex = "W2022648729",
    references = "alvarez1980extraterrestrial, doi1010160012821x78900717, doi101029jb082i005p00803, doi101029jb092ib08p08089, doi101029rg013i003p00001, doi101029rg018i001p00269, doi101038230042a0, doi101038274544a0, doi101038326143a0, doi101093petrology253713, doi101093petrology293625, doi101126science20844481095, doi101126science22746911161, doi101126science23848311237, doi101139e85009, doi101144gslmem19850100115, doi10130683d923ed16c711d78645000102c1865d, openalexw2989049194"
}

Stimulated by the wealth of frontier exploration data and deep seismic surveys about the North Atlantic margins, this publication was crafted to provide a comprehensive analysis of North Atlantic extension. The 40 papers in this volume are divided into 6 sections: concepts, North Atlantic perspectives, North American margins, European-African margins, North Sea and Barents Shelf, and analogs. This book is concerned primarily with the circum-North Atlantic data base. It is largely biased toward presentation and interpretation of data rather than being model driven. The book includes comparative stratigraphic columns for basins of the North Atlantic margins.

@book{doi101306m46497,
    author = "Tankard, A. J. and Balkwill, H R",
    title = "Extensional Tectonics and Stratigraphy of the North Atlantic Margins",
    year = "1989",
    booktitle = "American Association of Petroleum Geologists eBooks",
    abstract = "Stimulated by the wealth of frontier exploration data and deep seismic surveys about the North Atlantic margins, this publication was crafted to provide a comprehensive analysis of North Atlantic extension. The 40 papers in this volume are divided into 6 sections: concepts, North Atlantic perspectives, North American margins, European-African margins, North Sea and Barents Shelf, and analogs. This book is concerned primarily with the circum-North Atlantic data base. It is largely biased toward presentation and interpretation of data rather than being model driven. The book includes comparative stratigraphic columns for basins of the North Atlantic margins.",
    url = "https://doi.org/10.1306/m46497",
    doi = "10.1306/m46497",
    openalex = "W2099339012"
}

@misc{sacks1990kinematics1,
    author = "Sacks, P. E. and Secor, D. T. and Jr",
    title = "Kinematics of Late Paleozoic continental collision between Laurentia and Gondwana",
    year = "1990",
    howpublished = "Science, v. 250, no. 4988, p. 1702-1705",
    note = "talkorigins\_source = {true}; raw\_reference = {Sacks, P. E., and Secor, D. T., Jr., 1990, Kinematics of Late Paleozoic continental collision between Laurentia and Gondwana: Science, v. 250, no. 4988, p. 1702-1705.}"
}

@article{doi101016030192689490085x,
    author = "Ledru, P. and Johan, V. and Milési, J. and Tegyey, M.",
    title = "Markers of the last stages of the Palaeoproterozoic collision: evidence for a 2 Ga continent involving circum-South Atlantic provinces",
    year = "1994",
    journal = "Precambrian Research",
    url = "https://www.semanticscholar.org/paper/8953536a6d31ec4bb5eb73ea012d56077be7e6fb",
    doi = "10.1016/0301-9268(94)90085-X",
    is_oa = "true",
    number = "1-4",
    pages = "169-191",
    semanticscholar_citation_count = "250",
    semanticscholar_id = "8953536a6d31ec4bb5eb73ea012d56077be7e6fb",
    volume = "69",
    references = "doi101029tc005i003p00439"
}

Some of the most important, rapid, and enigmatic changes in our Earth’s environment and biota occurred during the Neoproterozoic Era (1000540 million years ago; Ma). Paramount among these changes are the rapid evolution of eukaryotes and appearance of metazoa (Knoll 1992, Conway Morris 1993), major episodes of continental glaciation that may have extended to low latitudes (Hambrey & Harland 1985), marked increases in the oxygen concentration of the atmosphere and hydrosphere (Derry et al 1992), the reappearance of sedimentary banded iron formations (BIF; James 1983), and striking temporal variations in the isotopic composition of C and Sr (Asmerom et al 1991, Derry et al 1992). Understanding the causes of and relationships between these changes is a challenging focus of interdisciplinary research, and there are compelling indications that the most important causes were tectonic (Des Marais et al 1992, Veevers 1990). For example, development of ocean basins may have been accompanied by the development of seafloor hydrothermal systems, which lowered the 87Sr/S6Sr of seawater, led to the development of BIF, and formed anoxic basins where organic carbon could be buried, thus leading to an increase in O~. Continental collision and formation of a supercontinent may have led to continental glaciation and an increase in the 87Sr/86Sr of seawater,

@article{doi101146annurevea22050194001535,
    author = "Stern, Robert J.",
    title = "ARC ASSEMBLY AND CONTINENTAL COLLISION IN THE NEOPROTEROZOIC EAST AFRICAN OROGEN: Implications for the Consolidation of Gondwanaland",
    year = "1994",
    journal = "Annual Review of Earth and Planetary Sciences",
    abstract = "Some of the most important, rapid, and enigmatic changes in our Earth’s environment and biota occurred during the Neoproterozoic Era (1000540 million years ago; Ma). Paramount among these changes are the rapid evolution of eukaryotes and appearance of metazoa (Knoll 1992, Conway Morris 1993), major episodes of continental glaciation that may have extended to low latitudes (Hambrey \& Harland 1985), marked increases in the oxygen concentration of the atmosphere and hydrosphere (Derry et al 1992), the reappearance of sedimentary banded iron formations (BIF; James 1983), and striking temporal variations in the isotopic composition of C and Sr (Asmerom et al 1991, Derry et al 1992). Understanding the causes of and relationships between these changes is a challenging focus of interdisciplinary research, and there are compelling indications that the most important causes were tectonic (Des Marais et al 1992, Veevers 1990). For example, development of ocean basins may have been accompanied by the development of seafloor hydrothermal systems, which lowered the 87Sr/S6Sr of seawater, led to the development of BIF, and formed anoxic basins where organic carbon could be buried, thus leading to an increase in O\textasciitilde . Continental collision and formation of a supercontinent may have led to continental glaciation and an increase in the 87Sr/86Sr of seawater,",
    url = "https://doi.org/10.1146/annurev.ea.22.050194.001535",
    doi = "10.1146/annurev.ea.22.050194.001535",
    openalex = "W2174216460"
}

Recent seismic results on the U.S. East Coast continental margin show that the zone between rifted continental and normal oceanic crust consists of thick (up to 25 km), high seismic velocity (ν p of 7.2–7.3 km s −1) crust, interpreted as mafic igneous rocks emplaced during Triassic/Jurassic continental rifting. The total volume of igneous rocks in this zone, which we call the East Coast Margin Igneous Province (ECMIP), may be as much as 2.7 × 10 6 km 3, placing the ECMIP among the world's large igneous provinces. We constrain the composition and origin of the thick, igneous crust by using a compilation of laboratory measurements to predict P wave velocities for rocks with the compositions of liquids produced by partial melting of mantle rocks. The high‐velocity crust was produced from partial melting of mantle peridotite, with smaller melt fractions (<10%) but at higher average pressures (≥2.0 GPa) than beneath normal mid‐ocean ridges. This requires higher than normal asthenospheric potential temperatures during rifting and a lid of lithosphere above upwelling asthenosphere to limit the minimum pressure of melting. Production of thick igneous crust at small melt fractions requires that the vertical flux of asthenosphere during rifting exceeded the lateral flux of lithosphere due to extension; that is, mantle “upwelling” was more rapid than lithospheric “spreading.” Thick igneous crust is strongly asymmetrical, extending up to 2000 km along the margin but only for about 80–100 km seaward. The rapid seaward transition to oceanic crust with normal thickness and seismic velocity implies that the thermal anomaly and relatively rapid upwelling lasted for only 5–8 m.y. Moreover, there is no crustal thickness anomaly in the Central Atlantic, in contrast to the North Atlantic where the influence of the Iceland plume created thick crust in a belt spanning the ocean from Greenland to the Faeroes Islands. These factors seem to preclude formation of thick igneous crust in response to a deep‐seated mantle plume. The ECMIP may have formed when high upper mantle temperatures induced asthenospheric upwelling. Magmatism and seafloor spreading dissipated the thermal anomaly in the upper mantle, after which normal oceanic crust formed along the Mid‐Atlantic Ridge.

@article{doi10102995jb00924,
    author = "Kelemen, P. B. and Holbrook, W. Steven",
    title = "Origin of thick, high‐velocity igneous crust along the U.S. East Coast Margin",
    year = "1995",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "Recent seismic results on the U.S. East Coast continental margin show that the zone between rifted continental and normal oceanic crust consists of thick (up to 25 km), high seismic velocity (ν p of 7.2–7.3 km s −1) crust, interpreted as mafic igneous rocks emplaced during Triassic/Jurassic continental rifting. The total volume of igneous rocks in this zone, which we call the East Coast Margin Igneous Province (ECMIP), may be as much as 2.7 × 10 6 km 3, placing the ECMIP among the world's large igneous provinces. We constrain the composition and origin of the thick, igneous crust by using a compilation of laboratory measurements to predict P wave velocities for rocks with the compositions of liquids produced by partial melting of mantle rocks. The high‐velocity crust was produced from partial melting of mantle peridotite, with smaller melt fractions (<10\%) but at higher average pressures (≥2.0 GPa) than beneath normal mid‐ocean ridges. This requires higher than normal asthenospheric potential temperatures during rifting and a lid of lithosphere above upwelling asthenosphere to limit the minimum pressure of melting. Production of thick igneous crust at small melt fractions requires that the vertical flux of asthenosphere during rifting exceeded the lateral flux of lithosphere due to extension; that is, mantle “upwelling” was more rapid than lithospheric “spreading.” Thick igneous crust is strongly asymmetrical, extending up to 2000 km along the margin but only for about 80–100 km seaward. The rapid seaward transition to oceanic crust with normal thickness and seismic velocity implies that the thermal anomaly and relatively rapid upwelling lasted for only 5–8 m.y. Moreover, there is no crustal thickness anomaly in the Central Atlantic, in contrast to the North Atlantic where the influence of the Iceland plume created thick crust in a belt spanning the ocean from Greenland to the Faeroes Islands. These factors seem to preclude formation of thick igneous crust in response to a deep‐seated mantle plume. The ECMIP may have formed when high upper mantle temperatures induced asthenospheric upwelling. Magmatism and seafloor spreading dissipated the thermal anomaly in the upper mantle, after which normal oceanic crust formed along the Mid‐Atlantic Ridge.",
    url = "https://doi.org/10.1029/95jb00924",
    doi = "10.1029/95jb00924",
    openalex = "W2088486731"
}

The Early Cretaceous South Atlantic continental break-up and initial sea-floor spreading were accompanied by large-scale, transient volcanism emplacing the Paraná-Etendeka continental flood basalts and voluminous extrusive constructions on the conjugate margins south of the Torres Arch–Abutment Plateau. On the North Namibia margin we interpret four main tectono-magmatic crustal units: (1) oceanic crust; (2) thickened oceanic crust covered by huge seaward-dipping wedges; (3) a c. 150 km wide break-up related rift zone partly covered by the dipping wedges; and (4) thicker continental crust, partly deformed by Palaeozoic extension, east of the Early Cretaceous rift. Similar settings also characterize other South Atlantic margin segments. We infer an up to 300 km wide and 2400 km long rift zone representing lithospheric extension leading to breakup and formation of the South Atlantic volcanic margins. Comparison with other volcanic margins demonstrates, in spite of local and regional differences, gross similarities in tectono-magmatic style, crustal units and dimensions.

@article{doi101144gsjgs15430465,
    author = "Gladczenko, Tadeusz P. and Hinz, K. and Eldholm, Olav and Meyer, H. and Neben, S. and Skogseid, Jakob",
    title = "South Atlantic volcanic margins",
    year = "1997",
    journal = "Journal of the Geological Society",
    abstract = "The Early Cretaceous South Atlantic continental break-up and initial sea-floor spreading were accompanied by large-scale, transient volcanism emplacing the Paraná-Etendeka continental flood basalts and voluminous extrusive constructions on the conjugate margins south of the Torres Arch–Abutment Plateau. On the North Namibia margin we interpret four main tectono-magmatic crustal units: (1) oceanic crust; (2) thickened oceanic crust covered by huge seaward-dipping wedges; (3) a c. 150 km wide break-up related rift zone partly covered by the dipping wedges; and (4) thicker continental crust, partly deformed by Palaeozoic extension, east of the Early Cretaceous rift. Similar settings also characterize other South Atlantic margin segments. We infer an up to 300 km wide and 2400 km long rift zone representing lithospheric extension leading to breakup and formation of the South Atlantic volcanic margins. Comparison with other volcanic margins demonstrates, in spite of local and regional differences, gross similarities in tectono-magmatic style, crustal units and dimensions.",
    url = "https://doi.org/10.1144/gsjgs.154.3.0465",
    doi = "10.1144/gsjgs.154.3.0465",
    openalex = "W2119313675"
}

During the Geophysical Measurements Across the Continental Margin of Namibia (MAMBA) experiments, offshore and onshore refraction and reflection seismic as well as magnetic data were collected. Together with the existing free‐air gravity data, these were used to derive two crustal sections across the ocean‐continent transition. The results show that the Early Cretaceous continental breakup and the separation of South Africa and South America were accompanied by excessive igneous activity offshore. Off Namibia we found a 150–200 km wide zone of igneous crust up to 25 km thick. The upper part of this zone consists of an extrusive section comprising three units of basaltic composition: two distinct wedges of seaward dipping reflectors (SDRs) separated by flat‐lying volcanic flows. The inner wedge of SDRs can be modeled as the source of a long‐wavelength magnetic anomaly that borders long parts of both South Atlantic margins (anomaly G). The crust underneath these extrusives is characterized by high‐velocity and high‐density material (average values 7 km s −1, 3×10 3 kg m −3). Free‐air gravity anomalies along both sides of the high‐density crust are interpreted as edge effects resulting from juxtaposition with normal oceanic and continental crust on either side. We define the abrupt landward termination of this zone as the continent‐ocean boundary, and consequently, the crust seaward is interpreted as exclusively igneous material and not intruded continental crust. Extrapolation of the interpreted geophysical features along the southwest African margin suggests a fast prograding narrow rift zone and sharp lithospheric rupture leading to the formation of a margin‐parallel magmatic belt south of the Walvis Ridge. The influence of the Tristan da Cunha mantle plume may explain the widening of this thick igneous crust near the Walvis Ridge.

@article{doi1010292000jb900227,
    author = "Bauer, Klaus and Neben, S. and Schreckenberger, Bernd and Emmermann, Rolf and Hinz, K. and Fechner, N. and Gohl, Karsten and Schulze, Albrecht and Trumbull, Robert B. and Weber, Klaus",
    title = "Deep structure of the Namibia continental margin as derived from integrated geophysical studies",
    year = "2000",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "During the Geophysical Measurements Across the Continental Margin of Namibia (MAMBA) experiments, offshore and onshore refraction and reflection seismic as well as magnetic data were collected. Together with the existing free‐air gravity data, these were used to derive two crustal sections across the ocean‐continent transition. The results show that the Early Cretaceous continental breakup and the separation of South Africa and South America were accompanied by excessive igneous activity offshore. Off Namibia we found a 150–200 km wide zone of igneous crust up to 25 km thick. The upper part of this zone consists of an extrusive section comprising three units of basaltic composition: two distinct wedges of seaward dipping reflectors (SDRs) separated by flat‐lying volcanic flows. The inner wedge of SDRs can be modeled as the source of a long‐wavelength magnetic anomaly that borders long parts of both South Atlantic margins (anomaly G). The crust underneath these extrusives is characterized by high‐velocity and high‐density material (average values 7 km s −1, 3×10 3 kg m −3). Free‐air gravity anomalies along both sides of the high‐density crust are interpreted as edge effects resulting from juxtaposition with normal oceanic and continental crust on either side. We define the abrupt landward termination of this zone as the continent‐ocean boundary, and consequently, the crust seaward is interpreted as exclusively igneous material and not intruded continental crust. Extrapolation of the interpreted geophysical features along the southwest African margin suggests a fast prograding narrow rift zone and sharp lithospheric rupture leading to the formation of a margin‐parallel magmatic belt south of the Walvis Ridge. The influence of the Tristan da Cunha mantle plume may explain the widening of this thick igneous crust near the Walvis Ridge.",
    url = "https://doi.org/10.1029/2000jb900227",
    doi = "10.1029/2000jb900227",
    openalex = "W2079851790",
    references = "doi101017cbo9780511524936, doi10102990eo00319, doi10102993rg02508, doi10102995jb00259, doi10102996jb03223, doi101029jb084ib11p05973, doi101029jb094ib06p07685, doi101029jz064i001p00049, doi101111j1365246x1991tb03461x, doi101111j1365246x1992tb00836x"
}

@article{s20a8e3d7d43ba699aba8f485896d9baf32a0da7c4,
    author = "Szatmari, P.",
    title = "AAPG Memoir 73, Chapter 6: Habitat of Petroleum Along the South Atlantic Margins",
    year = "2000",
    url = "https://www.semanticscholar.org/paper/0a8e3d7d43ba699aba8f485896d9baf32a0da7c4",
    is_oa = "true",
    semanticscholar_citation_count = "36",
    semanticscholar_id = "0a8e3d7d43ba699aba8f485896d9baf32a0da7c4"
}

Volcanic rifted margins evolve by a combination of extrusive flood volcanism, intrusive magmatism, extension, uplift, and erosion. The temporal and spatial relationships between these processes are influenced by the plate tectonic regime; the preexisting lithosphere (thickness, composition, geothermal gradient); the upper mantle (temperature and character); the magma production rate; and the prevailing climatic system. Of the Atlantic rifted margins, 75% are believed to be volcanic, the cumulative expression of thermotectonic processes over 200 m.y. Volcanic rifted margins also characterize Ethiopia-Yemen, India-Australia, and Africa-Madagascar. The transition from continental flood volcanism (or formation of a large igneous province) to ocean ridge processes (mid-ocean ridge basalt) is marked by a prerift to synrift transition with formation of a subaerial and/or submarine seaward-dipping reflector series and a significant thickness (to 15 km) of juvenile, high-velocity lower crust seaboard of the continental rifted margin. Herein we outline the similarities and differences between volcanic rifted margins worldwide and list some of their diagnostic features.

@incollection{doi10113008137236201,
    author = "Menzies, Martin and Klemperer, S. L. and Ebinger, C. J. and Baker, Joel A.",
    title = "Characteristics of volcanic rifted margins",
    year = "2002",
    booktitle = "Geological Society of America eBooks",
    abstract = "Volcanic rifted margins evolve by a combination of extrusive flood volcanism, intrusive magmatism, extension, uplift, and erosion. The temporal and spatial relationships between these processes are influenced by the plate tectonic regime; the preexisting lithosphere (thickness, composition, geothermal gradient); the upper mantle (temperature and character); the magma production rate; and the prevailing climatic system. Of the Atlantic rifted margins, 75\% are believed to be volcanic, the cumulative expression of thermotectonic processes over 200 m.y. Volcanic rifted margins also characterize Ethiopia-Yemen, India-Australia, and Africa-Madagascar. The transition from continental flood volcanism (or formation of a large igneous province) to ocean ridge processes (mid-ocean ridge basalt) is marked by a prerift to synrift transition with formation of a subaerial and/or submarine seaward-dipping reflector series and a significant thickness (to 15 km) of juvenile, high-velocity lower crust seaboard of the continental rifted margin. Herein we outline the similarities and differences between volcanic rifted margins worldwide and list some of their diagnostic features.",
    url = "https://doi.org/10.1130/0-8137-2362-0.1",
    doi = "10.1130/0-8137-2362-0.1",
    openalex = "W2335978012",
    references = "doi10100797894015780597, doi101016s0012821x98000892, doi1010291998jb900076, doi1010292000jb900227, doi10102995jb00924, doi101029gm100p0045, doi101029gm100p0145, doi101029gm100p0217, doi101144gsjgs15430465, doi101144gslsp19920680102"
}

Abstract The Archean Pilbara Craton contains five geologically distinct terranes – the East Pilbara, Karratha, Sholl, Regal and Kurrana Terranes – all of which are unconformably overlain by the 3.02‐ to 2.93‐Ga De Grey Superbasin. The 3.53–3.17 Ga East Pilbara Terrane (EP) represents the ancient nucleus of the craton that formed through three distinct mantle plume events at 3.53–3.43, 3.35–3.29 and 3.27–3.24 Ga. Each plume event resulted in eruption of thick dominantly basaltic volcanic successions on older crust to 3.72 Ga, and melting of crust to generate first tonalite‐trondhjemite‐granodiorite (TTG), and then progressively more evolved granitic magmas. In each case, plume magmatism was accompanied by uplift and crustal extension. The combination of conductive heating from below, thermal blanketing from above, and internal heating of buried granitoids during these events led to episodes of partial convective overturn of upper and middle crust. These mantle melting events caused severe depletion of the subcontinental lithospheric mantle, making the EP a stable, buoyant, unsubductable continent by c. 3.2 Ga. Extension accompanying the latest event led to rifting of the protocontinent margins at between 3.2 and 3.17 Ga. After 3.2 Ga, horizontal tectonic forces dominated over vertical forces, as revealed by the geology of the three terranes (Karratha, Sholl and Regal) of the West Pilbara Superterrane. The c. 3.12‐Ga Whundo Group of the Sholl Terrane is a fault bounded, 10‐km‐thick volcanic succession with geochemical characteristics of modern oceanic arcs (including boninites and evidence for flux melting) that indicate steep Archean subduction. At 3.07 Ga, the 3.12‐Ga Sholl Terrane, 3.27‐Ga Karratha Terrane and c. 3.2‐Ga Regal Terrane accreted together and onto the EP during the Prinsep Orogeny. This was followed by development of the De Grey Superbasin – an intracontinental sag basin and widespread plutonism (2.99–2.93 Ga) as a result of orogenic relaxation and slab break off. Craton‐wide compressional deformation at 2.95–2.93 Ga culminated with 2.91‐Ga accretion of the 3.18 Ga Kurrana Terrane with the EP. This compression caused amplification of the dome‐and‐keel structure in the EP. Final cratonization was effected by emplacement of 2.89–2.83 Ga post‐tectonic granites.

@article{doi101111j13653121200600723x,
    author = "Kranendonk, Martin J. Van and Smithies, R.H. and Hickman, Arthur H. and Champion, D.C.",
    title = "Review: secular tectonic evolution of Archean continental crust: interplay between horizontal and vertical processes in the formation of the Pilbara Craton, Australia",
    year = "2007",
    journal = "Terra Nova",
    abstract = "Abstract The Archean Pilbara Craton contains five geologically distinct terranes – the East Pilbara, Karratha, Sholl, Regal and Kurrana Terranes – all of which are unconformably overlain by the 3.02‐ to 2.93‐Ga De Grey Superbasin. The 3.53–3.17 Ga East Pilbara Terrane (EP) represents the ancient nucleus of the craton that formed through three distinct mantle plume events at 3.53–3.43, 3.35–3.29 and 3.27–3.24 Ga. Each plume event resulted in eruption of thick dominantly basaltic volcanic successions on older crust to 3.72 Ga, and melting of crust to generate first tonalite‐trondhjemite‐granodiorite (TTG), and then progressively more evolved granitic magmas. In each case, plume magmatism was accompanied by uplift and crustal extension. The combination of conductive heating from below, thermal blanketing from above, and internal heating of buried granitoids during these events led to episodes of partial convective overturn of upper and middle crust. These mantle melting events caused severe depletion of the subcontinental lithospheric mantle, making the EP a stable, buoyant, unsubductable continent by c. 3.2 Ga. Extension accompanying the latest event led to rifting of the protocontinent margins at between 3.2 and 3.17 Ga. After 3.2 Ga, horizontal tectonic forces dominated over vertical forces, as revealed by the geology of the three terranes (Karratha, Sholl and Regal) of the West Pilbara Superterrane. The c. 3.12‐Ga Whundo Group of the Sholl Terrane is a fault bounded, 10‐km‐thick volcanic succession with geochemical characteristics of modern oceanic arcs (including boninites and evidence for flux melting) that indicate steep Archean subduction. At 3.07 Ga, the 3.12‐Ga Sholl Terrane, 3.27‐Ga Karratha Terrane and c. 3.2‐Ga Regal Terrane accreted together and onto the EP during the Prinsep Orogeny. This was followed by development of the De Grey Superbasin – an intracontinental sag basin and widespread plutonism (2.99–2.93 Ga) as a result of orogenic relaxation and slab break off. Craton‐wide compressional deformation at 2.95–2.93 Ga culminated with 2.91‐Ga accretion of the 3.18 Ga Kurrana Terrane with the EP. This compression caused amplification of the dome‐and‐keel structure in the EP. Final cratonization was effected by emplacement of 2.89–2.83 Ga post‐tectonic granites.",
    url = "https://doi.org/10.1111/j.1365-3121.2006.00723.x",
    doi = "10.1111/j.1365-3121.2006.00723.x",
    openalex = "W2010249788",
    references = "doi101038nature04764, doi10113008137236201"
}

Abstract The South Atlantic Ocean evolved after rupture of the São Francisco–Congo–Rio de la Plata–Kalahari cratonic landmass and the Late Proterozoic fold belts. Break-up in the South Atlantic realm developed diachronously: rifting started in the south (Argentina) during the Jurassic and progressed towards the equatorial segment. The central portion was controlled by a rift-resistant cratonic nucleus (the São Francisco–Congo craton) and as a result underwent development of narrow basins; parts controlled by Neoproterozoic fold belts developed wide basins. The final break-up of western Gondwana and the onset of plate divergence were marked by thick wedges of seaward-dipping reflectors, located near the incipient ocean-ridge spreading centre that had already been formed by the time Aptian evaporites were deposited. Subsequently, a few episodes of intraplate tectonic and magmatic activity affected the Santos, Campos and Espírito Santo basins. Post-break up development of the offshore basins was affected by gravity gliding over the Aptian evaporites. Continental uplift may be invoked as the main cause of salt mobilization, generating prograding clastic wedges that thickened basin-wards and produced a loading effect on the salt basin. Coupled with onshore erosional unloading and the effects of the gravity gliding, this probably resulted in further flexural uplift of the continental margin.

@article{doi101144sp29419,
    author = "Mohriak, Webster Ueipass and Němčok, Michal and Enciso, G.",
    title = "South Atlantic divergent margin evolution: rift-border uplift and salt tectonics in the basins of SE Brazil",
    year = "2008",
    journal = "Geological Society London Special Publications",
    abstract = "Abstract The South Atlantic Ocean evolved after rupture of the São Francisco–Congo–Rio de la Plata–Kalahari cratonic landmass and the Late Proterozoic fold belts. Break-up in the South Atlantic realm developed diachronously: rifting started in the south (Argentina) during the Jurassic and progressed towards the equatorial segment. The central portion was controlled by a rift-resistant cratonic nucleus (the São Francisco–Congo craton) and as a result underwent development of narrow basins; parts controlled by Neoproterozoic fold belts developed wide basins. The final break-up of western Gondwana and the onset of plate divergence were marked by thick wedges of seaward-dipping reflectors, located near the incipient ocean-ridge spreading centre that had already been formed by the time Aptian evaporites were deposited. Subsequently, a few episodes of intraplate tectonic and magmatic activity affected the Santos, Campos and Espírito Santo basins. Post-break up development of the offshore basins was affected by gravity gliding over the Aptian evaporites. Continental uplift may be invoked as the main cause of salt mobilization, generating prograding clastic wedges that thickened basin-wards and produced a loading effect on the salt basin. Coupled with onshore erosional unloading and the effects of the gravity gliding, this probably resulted in further flexural uplift of the continental margin.",
    url = "https://doi.org/10.1144/sp294.19",
    doi = "10.1144/sp294.19",
    openalex = "W2065375137",
    references = "doi101111j1365246x200502668x"
}

Nares Strait separating Greenland and northernmost Canada is floored by continental crust. Most palaeogeographic reconstructions of Laurentia and the North Atlantic region model the seaway as the site of massive sinistral strike–slip and/or compression/transpression, subduction and collision, the supposed manifestations of the hypothetical Wegener Fault. However, these reconstructions fail to take into account the bedrock geology that represents within‐plate evolution. Both sides of Smith Sound, the southernmost part of Nares Strait, expose the same early Proterozoic to early Palaeozoic assemblages that are unaffected by seaway‐related tectonism or thermal activity. Smith Sound is an intact crustal block or `linchpin' demonstrating that there was no independent Greenland plate. North‐west Greenland was not a leading plate margin neither was Nares Strait the site of the plate boundary between Greenland and North America. The Wegener Fault does not exist. The Smith Sound linchpin constitutes a key constraint that must be respected in any palaeogeographic reconstruction of the region.

@article{doi101111j13653121200800845x,
    author = "Dawes, P.",
    title = "Precambrian–Palaeozoic geology of Smith Sound, Canada and Greenland: key constraint to palaeogeographic reconstructions of northern Laurentia and the North Atlantic region",
    year = "2009",
    journal = "Terra Nova",
    abstract = "Nares Strait separating Greenland and northernmost Canada is floored by continental crust. Most palaeogeographic reconstructions of Laurentia and the North Atlantic region model the seaway as the site of massive sinistral strike–slip and/or compression/transpression, subduction and collision, the supposed manifestations of the hypothetical Wegener Fault. However, these reconstructions fail to take into account the bedrock geology that represents within‐plate evolution. Both sides of Smith Sound, the southernmost part of Nares Strait, expose the same early Proterozoic to early Palaeozoic assemblages that are unaffected by seaway‐related tectonism or thermal activity. Smith Sound is an intact crustal block or `linchpin' demonstrating that there was no independent Greenland plate. North‐west Greenland was not a leading plate margin neither was Nares Strait the site of the plate boundary between Greenland and North America. The Wegener Fault does not exist. The Smith Sound linchpin constitutes a key constraint that must be respected in any palaeogeographic reconstruction of the region.",
    url = "https://www.semanticscholar.org/paper/cc6a0b1d26acba788f86435443544b8457483b01",
    doi = "10.1111/j.1365-3121.2008.00845.x",
    is_oa = "true",
    number = "1",
    pages = "1-13",
    semanticscholar_citation_count = "42",
    semanticscholar_id = "cc6a0b1d26acba788f86435443544b8457483b01",
    volume = "21"
}

Abstract The simplest models of passive margins would suggest that they are characterized by tectonic quiescence as they experienced gentle thermal subsidence following the extensional events that originally formed them. Analysis of newly acquired and pre-existing 2D seismic data from the Rockall Plateau to the Faroe Shelf, however, has confirmed that the NE Atlantic Margin was the site of significant active deformation. Seismic data have revealed the presence of numerous compression-related Cenozoic folds, such as the Hatton Bank, Alpin, Ymir Ridge and Wyville–Thomson Ridge Anticlines. The distribution, timing of formation and nature of these structures have provided new insights into the controls and effects of contractional deformation in the region. Growth of these compressional features occurred in five main phases: Thanetian, late Ypresian, late Lutetian, Late Eocene (C30) and Early Oligocene. Compression has been linked to hotspot-influenced ridge push, far-field Alpine and Pyrenean compression, asthenospheric upwelling and associated depth-dependent stretching. Regional studies make it clear that compression can have a profound effect on seabed bathymetry and consequent bottom-water current activity. Bottom-water currents have directly formed the early Late Oligocene, late Early Miocene (C20), Late Miocene–Early Pliocene, and late Early Pliocene (C10) unconformities. The present-day Norwegian Sea Overflow (NSO) from the Faroe–Shetland Channel into the Rockall Trough is restricted by the Wyville–Ymir Ridge Complex, and takes place via the syncline (Auðhumla Basin) between the two ridges. The Auðhumla Basin Syncline is now thought to have controlled the path of the NSO into the Rockall Trough and the resulting unconformity formation and sedimentation therein, no later than the Mid Miocene.

@article{doi1011440070963,
    author = "Tuitt, Adrian and Underhill, John R. and Ritchie, J. D. and Johnson, Howard D. and Hitchen, K.",
    title = "Timing, controls and consequences of compression in the Rockall-Faroe area of the NE Atlantic Margin",
    year = "2010",
    journal = "Geological Society London Petroleum Geology Conference series",
    abstract = "Abstract The simplest models of passive margins would suggest that they are characterized by tectonic quiescence as they experienced gentle thermal subsidence following the extensional events that originally formed them. Analysis of newly acquired and pre-existing 2D seismic data from the Rockall Plateau to the Faroe Shelf, however, has confirmed that the NE Atlantic Margin was the site of significant active deformation. Seismic data have revealed the presence of numerous compression-related Cenozoic folds, such as the Hatton Bank, Alpin, Ymir Ridge and Wyville–Thomson Ridge Anticlines. The distribution, timing of formation and nature of these structures have provided new insights into the controls and effects of contractional deformation in the region. Growth of these compressional features occurred in five main phases: Thanetian, late Ypresian, late Lutetian, Late Eocene (C30) and Early Oligocene. Compression has been linked to hotspot-influenced ridge push, far-field Alpine and Pyrenean compression, asthenospheric upwelling and associated depth-dependent stretching. Regional studies make it clear that compression can have a profound effect on seabed bathymetry and consequent bottom-water current activity. Bottom-water currents have directly formed the early Late Oligocene, late Early Miocene (C20), Late Miocene–Early Pliocene, and late Early Pliocene (C10) unconformities. The present-day Norwegian Sea Overflow (NSO) from the Faroe–Shetland Channel into the Rockall Trough is restricted by the Wyville–Ymir Ridge Complex, and takes place via the syncline (Auðhumla Basin) between the two ridges. The Auðhumla Basin Syncline is now thought to have controlled the path of the NSO into the Rockall Trough and the resulting unconformity formation and sedimentation therein, no later than the Mid Miocene.",
    url = "https://doi.org/10.1144/0070963",
    doi = "10.1144/0070963",
    openalex = "W2109695247",
    references = "burke1982geology"
}

ABSTRACT The discovery of giant hydrocarbon reservoirs in the pre-salt sequence of the deep-water Brazilian rifted margin together with the new acquisition of high-quality reflection and refraction seismic surveys across many rifted margins worldwide has attracted the interest of industry and researchers to deep-water rifted margins. For the first time, the new data sets enable the imaging and description of the pre-salt structures, which indicate that deep-water rifted margins are very different from what classical models had predicted thus far. Instead of the expected fault-bounded basins and a sharp ocean–continent boundary, the new data suggest the existence of a sag basin lying on hyper-extended crust with little indication for brittle high-angle faulting, a transitional domain between continental and oceanic crust showing neither characteristics of oceanic nor continental material, and very asymmetrical distal conjugate rifted margins. These observations raise significant doubts on the validity of the classical concepts used in rheology, mechanics and isostasy to explain extensional systems leading to seafloor spreading. They also require new concepts and more data in order to understand how these rifted margins evolved in time and space. This has important implications for the exploration and evaluation of petroleum systems in the frontier areas of hydrocarbon exploration. In this study we publish two multi-channel seismic sections across the Angola and conjugate Brazilian rifted margins that we consider as ‘type’ sections for hyper-extended magma-poor rifted margins in the South Atlantic. The aim of this study is to discuss various possible interpretations and models to explain the high-resolution seismic images presented in this paper.

@article{doi1011441354079309904,
    author = "Unternehr, Patrick and Péron‐Pinvidic, Gwenn and Manatschal, Giänreto and Sutra, Emilie",
    title = "Hyper-extended crust in the South Atlantic: in search of a model",
    year = "2010",
    journal = "Petroleum Geoscience",
    abstract = "ABSTRACT The discovery of giant hydrocarbon reservoirs in the pre-salt sequence of the deep-water Brazilian rifted margin together with the new acquisition of high-quality reflection and refraction seismic surveys across many rifted margins worldwide has attracted the interest of industry and researchers to deep-water rifted margins. For the first time, the new data sets enable the imaging and description of the pre-salt structures, which indicate that deep-water rifted margins are very different from what classical models had predicted thus far. Instead of the expected fault-bounded basins and a sharp ocean–continent boundary, the new data suggest the existence of a sag basin lying on hyper-extended crust with little indication for brittle high-angle faulting, a transitional domain between continental and oceanic crust showing neither characteristics of oceanic nor continental material, and very asymmetrical distal conjugate rifted margins. These observations raise significant doubts on the validity of the classical concepts used in rheology, mechanics and isostasy to explain extensional systems leading to seafloor spreading. They also require new concepts and more data in order to understand how these rifted margins evolved in time and space. This has important implications for the exploration and evaluation of petroleum systems in the frontier areas of hydrocarbon exploration. In this study we publish two multi-channel seismic sections across the Angola and conjugate Brazilian rifted margins that we consider as ‘type’ sections for hyper-extended magma-poor rifted margins in the South Atlantic. The aim of this study is to discuss various possible interpretations and models to explain the high-resolution seismic images presented in this paper.",
    url = "https://doi.org/10.1144/1354-079309-904",
    doi = "10.1144/1354-079309-904",
    openalex = "W2075772841",
    references = "doi101111j1365246x200502668x"
}

[1] Seismic reflection and refraction profiles, and potential field data, complemented by crustal-scale gravity modeling and plate reconstructions are used to study the evolution of the central and south segments of the South Atlantic conjugate margins. The central segment is characterized by a hyperextended continent-ocean transitional domain that shows evidence of rotated fault blocks and a detachment surface active during rifting. A polyphase rifting evolution mode, associated with a complex time-dependent thermal structure of the lithosphere, is substantiated for the central segment that is not a “magma-poor” end-member. Increase of volcanic activity during the late stages of rifting may have “interrupted” the extensional system implying a failed exhumation phase that was replaced instead by continental breakup and emplacement of fully igneous crust. The continent-ocean transitional domain along the “magma-dominated” south segment is characterized by a large volume of flood basalts and high-velocity/high-density lower crust. The northern province of the south segment is characterized by symmetrical seaward-dipping reflections and symmetrical continent-ocean transitional domain. The influence of the Tristan da Cunha plume on this province is very likely. The central province of the south segment is characterized by along-strike tectonomagmatic asymmetry, which can be caused by the initial continental stretching and accompanying magmatism rather than by the subsequent seafloor spreading. The Tristan da Cunha plume on the central province may have influenced the volume of magmatism but did not necessarily alter the process of rifted margin formation, implying that the central province of the south segment may have much in common with “magma-poor” margins.

@article{doi1010292010jb007686,
    author = "Blaich, Olav A. and Faleide, Jan Inge and Tsikalas, Filippos",
    title = "Crustal breakup and continent-ocean transition at South Atlantic conjugate margins",
    year = "2011",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "[1] Seismic reflection and refraction profiles, and potential field data, complemented by crustal-scale gravity modeling and plate reconstructions are used to study the evolution of the central and south segments of the South Atlantic conjugate margins. The central segment is characterized by a hyperextended continent-ocean transitional domain that shows evidence of rotated fault blocks and a detachment surface active during rifting. A polyphase rifting evolution mode, associated with a complex time-dependent thermal structure of the lithosphere, is substantiated for the central segment that is not a “magma-poor” end-member. Increase of volcanic activity during the late stages of rifting may have “interrupted” the extensional system implying a failed exhumation phase that was replaced instead by continental breakup and emplacement of fully igneous crust. The continent-ocean transitional domain along the “magma-dominated” south segment is characterized by a large volume of flood basalts and high-velocity/high-density lower crust. The northern province of the south segment is characterized by symmetrical seaward-dipping reflections and symmetrical continent-ocean transitional domain. The influence of the Tristan da Cunha plume on this province is very likely. The central province of the south segment is characterized by along-strike tectonomagmatic asymmetry, which can be caused by the initial continental stretching and accompanying magmatism rather than by the subsequent seafloor spreading. The Tristan da Cunha plume on the central province may have influenced the volume of magmatism but did not necessarily alter the process of rifted margin formation, implying that the central province of the south segment may have much in common with “magma-poor” margins.",
    url = "https://doi.org/10.1029/2010jb007686",
    doi = "10.1029/2010jb007686",
    openalex = "W2067237660",
    references = "doi1010160012821x78900717, doi1010160191814189900369, doi1010292000jb900227, doi1010292007gc001743, doi10102991jb01485, doi10102996jb03223, doi101029jb084ib11p05973, doi101029jb094ib06p07685, doi101038291645a0, doi101139e85009, openalexw191472345"
}

Along the northern border of Africa, Pangea breakup has been diachronic. During the Jurassic, the Alpine Tethys propagated northeastward from the Atlantic to the Alps. During the Permian, the Neo‐Tethys propagated westward from Oman to northwestern Arabia. Then a secondary and late branch of Neo‐Tethys gave birth to the East Mediterranean basin. Finally the two oceans connected at end of Jurassic times, achieving the development of Africa northern plate boundary. By the Late Cretaceous, convergence between Africa and Eurasia led to the progressive closure of the Tethys realm. The continental collision is not completely achieved, and the different segments of the confrontation zone (Maghreb, central and East Mediterranean, Zagros, and Oman) expose different stages of the process. However, we emphasize the existence of synchronous geodynamic events from one end of the system to the other, although they do not have the same meaning. Two of them are particularly important. The Campanian‐Santonian (C‐S) event corresponds to (1) obduction and exhumation of high‐pressure–low‐temperature metamorphic rocks around the Arabian promontory, (2) inversion along the margins of the East Mediterranean basins, and (3) lithosphere buckling in the Atlas system (Maghreb) and adjacent Sahara platform. The middle‐late Eocene (MLE) event corresponds to (1) the onset of collision at the northern corner of Arabia, (2) the onset of slab retreat in the Mediterranean, and (3) inversion along the margin of the East Mediterranean as well as in the Atlas. The C‐S event coincides with a change in plate kinematics resulting in an abrupt increase of convergence velocity. The MLE event coincides with a period of strong coupling between the Africa and Eurasia plates and an abrupt decrease of convergence velocity. In the middle of the system, the central Mediterranean seems to escape to the effects of convergence and is the site of quite permanent extensional movements since the Triassic.

@article{doi1010292010tc002691,
    author = "de Lamotte, Dominique Frizon and Raulin, Camille and Mouchot, Nicolas and Wrobel‐Daveau, Jean‐Christophe and Blanpied, Christian and Ringenbach, Jean‐Claude",
    title = "The southernmost margin of the Tethys realm during the Mesozoic and Cenozoic: Initial geometry and timing of the inversion processes",
    year = "2011",
    journal = "Tectonics",
    abstract = "Along the northern border of Africa, Pangea breakup has been diachronic. During the Jurassic, the Alpine Tethys propagated northeastward from the Atlantic to the Alps. During the Permian, the Neo‐Tethys propagated westward from Oman to northwestern Arabia. Then a secondary and late branch of Neo‐Tethys gave birth to the East Mediterranean basin. Finally the two oceans connected at end of Jurassic times, achieving the development of Africa northern plate boundary. By the Late Cretaceous, convergence between Africa and Eurasia led to the progressive closure of the Tethys realm. The continental collision is not completely achieved, and the different segments of the confrontation zone (Maghreb, central and East Mediterranean, Zagros, and Oman) expose different stages of the process. However, we emphasize the existence of synchronous geodynamic events from one end of the system to the other, although they do not have the same meaning. Two of them are particularly important. The Campanian‐Santonian (C‐S) event corresponds to (1) obduction and exhumation of high‐pressure–low‐temperature metamorphic rocks around the Arabian promontory, (2) inversion along the margins of the East Mediterranean basins, and (3) lithosphere buckling in the Atlas system (Maghreb) and adjacent Sahara platform. The middle‐late Eocene (MLE) event corresponds to (1) the onset of collision at the northern corner of Arabia, (2) the onset of slab retreat in the Mediterranean, and (3) inversion along the margin of the East Mediterranean as well as in the Atlas. The C‐S event coincides with a change in plate kinematics resulting in an abrupt increase of convergence velocity. The MLE event coincides with a period of strong coupling between the Africa and Eurasia plates and an abrupt decrease of convergence velocity. In the middle of the system, the central Mediterranean seems to escape to the effects of convergence and is the site of quite permanent extensional movements since the Triassic.",
    url = "https://doi.org/10.1029/2010tc002691",
    doi = "10.1029/2010tc002691",
    openalex = "W1503493870",
    references = "doi101016jearscirev200908001, doi101016s0012821x03004527, doi102113geoarabia0504527, doi102113geoarabia0603445, doi102113geoarabia140217"
}

Studies conducted in present‐day magma‐poor rifted margins reveal that the transition from weakly thinned continental crust (∼30 km) in proximal margins to hyper‐extended crust (≤10 km) in distal margins occurs within a narrow zone, referred to as the necking zone. We have identified relics of a necking zone and of the adjacent distal margin in the Campo, Grosina and Bernina units of the fossil Alpine Tethys margins and investigated the deformation and sedimentary processes associated with extreme crustal thinning during rifting. Within the basement rocks of the necking zone, we show that: (1) Grosina basement represents pre‐rift upper/middle crust, while the underlying Campo unit consists of pre‐rift middle/lower crust that was exhumed and cooled below ∼300°C by ca. 180 Ma, when rifting started to localize within the future distal margin; (2) the juxtaposition of the Campo and Grosina units was accommodated by the Eita shear zone, which is interpreted as a decollement/decoupling horizon active at mid‐crustal depth at 180–205 Ma; (3) the Grosina unit hosts a large‐scale brittle detachment fault. Our observations suggest that crustal thinning, accommodated through the necking zone, is the result of the interplay between detachment faulting in the brittle layers and decoupling and thinning in ductile quartzo‐feldspatic middle crustal levels along localized ductile decollements. The excision of ductile mid‐crustal layers and the progressive embrittlement of the crust enables major detachment faults to cut into the underlying mantle, exhuming it to the seafloor. This structural evolution can explain the first‐order crustal architecture of many present‐day rifted margins.

@article{doi1010292011tc002961,
    author = "Mohn, Geoffroy and Manatschal, G. and Beltrando, Marco and Masini, Emmanuel and Kusznir, Nick",
    title = "Necking of continental crust in magma‐poor rifted margins: Evidence from the fossil Alpine Tethys margins",
    year = "2012",
    journal = "Tectonics",
    abstract = "Studies conducted in present‐day magma‐poor rifted margins reveal that the transition from weakly thinned continental crust (∼30 km) in proximal margins to hyper‐extended crust (≤10 km) in distal margins occurs within a narrow zone, referred to as the necking zone. We have identified relics of a necking zone and of the adjacent distal margin in the Campo, Grosina and Bernina units of the fossil Alpine Tethys margins and investigated the deformation and sedimentary processes associated with extreme crustal thinning during rifting. Within the basement rocks of the necking zone, we show that: (1) Grosina basement represents pre‐rift upper/middle crust, while the underlying Campo unit consists of pre‐rift middle/lower crust that was exhumed and cooled below ∼300°C by ca. 180 Ma, when rifting started to localize within the future distal margin; (2) the juxtaposition of the Campo and Grosina units was accommodated by the Eita shear zone, which is interpreted as a decollement/decoupling horizon active at mid‐crustal depth at 180–205 Ma; (3) the Grosina unit hosts a large‐scale brittle detachment fault. Our observations suggest that crustal thinning, accommodated through the necking zone, is the result of the interplay between detachment faulting in the brittle layers and decoupling and thinning in ductile quartzo‐feldspatic middle crustal levels along localized ductile decollements. The excision of ductile mid‐crustal layers and the progressive embrittlement of the crust enables major detachment faults to cut into the underlying mantle, exhuming it to the seafloor. This structural evolution can explain the first‐order crustal architecture of many present‐day rifted margins.",
    url = "https://doi.org/10.1029/2011tc002961",
    doi = "10.1029/2011tc002961",
    openalex = "W1548147260",
    references = "doi1010292000jb900325, doi101111j1365246x200502668x"
}

Abstract. The South Atlantic rift basin evolved as a branch of a large Jurassic–Cretaceous intraplate rift zone between the African and South American plates during the final break-up of western Gondwana. While the relative motions between South America and Africa for post-break-up times are well resolved, many issues pertaining to the fit reconstruction and particularly the relation between kinematics and lithosphere dynamics during pre-break-up remain unclear in currently published plate models. We have compiled and assimilated data from these intraplated rifts and constructed a revised plate kinematic model for the pre-break-up evolution of the South Atlantic. Based on structural restoration of the conjugate South Atlantic margins and intracontinental rift basins in Africa and South America, we achieve a tight-fit reconstruction which eliminates the need for previously inferred large intracontinental shear zones, in particular in Patagonian South America. By quantitatively accounting for crustal deformation in the Central and West African Rift Zones, we have been able to indirectly construct the kinematic history of the pre-break-up evolution of the conjugate west African–Brazilian margins. Our model suggests a causal link between changes in extension direction and velocity during continental extension and the generation of marginal structures such as the enigmatic pre-salt sag basin and the São Paulo High. We model an initial E–W-directed extension between South America and Africa (fixed in present-day position) at very low extensional velocities from 140 Ma until late Hauterivian times (≈126 Ma) when rift activity along in the equatorial Atlantic domain started to increase significantly. During this initial ≈14 Myr-long stretching episode the pre-salt basin width on the conjugate Brazilian and west African margins is generated. An intermediate stage between ≈126 Ma and base Aptian is characterised by strain localisation, rapid lithospheric weakening in the equatorial Atlantic domain, resulting in both progressively increasing extensional velocities as well as a significant rotation of the extension direction to NE–SW. From base Aptian onwards diachronous lithospheric break-up occurred along the central South Atlantic rift, first in the Sergipe–Alagoas/Rio Muni margin segment in the northernmost South Atlantic. Final break-up between South America and Africa occurred in the conjugate Santos–Benguela margin segment at around 113 Ma and in the equatorial Atlantic domain between the Ghanaian Ridge and the Piauí-Ceará margin at 103 Ma. We conclude that such a multi-velocity, multi-directional rift history exerts primary control on the evolution of these conjugate passive-margin systems and can explain the first-order tectonic structures along the South Atlantic and possibly other passive margins.

@article{doi105194se42152013,
    author = "Heine, Christian and Zoethout, J. and Müller, R. Dietmar",
    title = "Kinematics of the South Atlantic rift",
    year = "2013",
    journal = "Solid Earth",
    abstract = "Abstract. The South Atlantic rift basin evolved as a branch of a large Jurassic–Cretaceous intraplate rift zone between the African and South American plates during the final break-up of western Gondwana. While the relative motions between South America and Africa for post-break-up times are well resolved, many issues pertaining to the fit reconstruction and particularly the relation between kinematics and lithosphere dynamics during pre-break-up remain unclear in currently published plate models. We have compiled and assimilated data from these intraplated rifts and constructed a revised plate kinematic model for the pre-break-up evolution of the South Atlantic. Based on structural restoration of the conjugate South Atlantic margins and intracontinental rift basins in Africa and South America, we achieve a tight-fit reconstruction which eliminates the need for previously inferred large intracontinental shear zones, in particular in Patagonian South America. By quantitatively accounting for crustal deformation in the Central and West African Rift Zones, we have been able to indirectly construct the kinematic history of the pre-break-up evolution of the conjugate west African–Brazilian margins. Our model suggests a causal link between changes in extension direction and velocity during continental extension and the generation of marginal structures such as the enigmatic pre-salt sag basin and the São Paulo High. We model an initial E–W-directed extension between South America and Africa (fixed in present-day position) at very low extensional velocities from 140 Ma until late Hauterivian times (≈126 Ma) when rift activity along in the equatorial Atlantic domain started to increase significantly. During this initial ≈14 Myr-long stretching episode the pre-salt basin width on the conjugate Brazilian and west African margins is generated. An intermediate stage between ≈126 Ma and base Aptian is characterised by strain localisation, rapid lithospheric weakening in the equatorial Atlantic domain, resulting in both progressively increasing extensional velocities as well as a significant rotation of the extension direction to NE–SW. From base Aptian onwards diachronous lithospheric break-up occurred along the central South Atlantic rift, first in the Sergipe–Alagoas/Rio Muni margin segment in the northernmost South Atlantic. Final break-up between South America and Africa occurred in the conjugate Santos–Benguela margin segment at around 113 Ma and in the equatorial Atlantic domain between the Ghanaian Ridge and the Piauí-Ceará margin at 103 Ma. We conclude that such a multi-velocity, multi-directional rift history exerts primary control on the evolution of these conjugate passive-margin systems and can explain the first-order tectonic structures along the South Atlantic and possibly other passive margins.",
    url = "https://doi.org/10.5194/se-4-215-2013",
    doi = "10.5194/se-4-215-2013",
    openalex = "W1992192773",
    references = "doi1010160012821x78900717, doi101016jearscirev201203002, doi101016jprecamres200704021, doi1010292001gc000252, doi1010292007gc001743, doi10102998eo00426, doi101029jb094ib06p07685, doi101126science23547931156, doi101144sp2902, doi102110pec95040129, openalexw2989049194"
}

When continents break apart, continental crust and lithosphere are thinned until break-up is achieved and an oceanic basin is formed. The most remarkable and least understood structures associated with this process are up to 200 km wide areas of hyper-extended continental crust, which are partitioned between conjugate margins with pronounced asymmetry. Here we show, using high-resolution thermo-mechanical modelling, that hyper-extended crust and margin asymmetry are produced by steady state rift migration. We demonstrate that rift migration is accomplished by sequential, oceanward-younging, upper crustal faults, and is balanced through lower crustal flow. Constraining our model with a new South Atlantic plate reconstruction, we demonstrate that larger extension velocities may account for southward increasing width and asymmetry of these conjugate magma-poor margins. Our model challenges conventional ideas of rifted margin evolution, as it implies that during rift migration large amounts of material are transferred from one side of the rift zone to the other.

@article{doi101038ncomms5014,
    author = "Brune, Sascha and Heine, Christian and Pérez‐Gussinyé, Marta and Sobolev, S. V.",
    title = "Rift migration explains continental margin asymmetry and crustal hyper-extension",
    year = "2014",
    journal = "Nature Communications",
    abstract = "When continents break apart, continental crust and lithosphere are thinned until break-up is achieved and an oceanic basin is formed. The most remarkable and least understood structures associated with this process are up to 200 km wide areas of hyper-extended continental crust, which are partitioned between conjugate margins with pronounced asymmetry. Here we show, using high-resolution thermo-mechanical modelling, that hyper-extended crust and margin asymmetry are produced by steady state rift migration. We demonstrate that rift migration is accomplished by sequential, oceanward-younging, upper crustal faults, and is balanced through lower crustal flow. Constraining our model with a new South Atlantic plate reconstruction, we demonstrate that larger extension velocities may account for southward increasing width and asymmetry of these conjugate magma-poor margins. Our model challenges conventional ideas of rifted margin evolution, as it implies that during rift migration large amounts of material are transferred from one side of the rift zone to the other.",
    url = "https://doi.org/10.1038/ncomms5014",
    doi = "10.1038/ncomms5014",
    openalex = "W2056837513",
    references = "doi1010160191814180900486, doi101016jearscirev200908001, doi101016jfuture200307011, doi101029138gm06, doi1010291999jb900301, doi1010292000jb900325, doi1010292002gc000433, doi1010292006tc001970, doi1010292010jb007686, doi10102991jb01485, doi10102995jb00259, doi101038nature02128, doi101111j1365246x200904137x, doi101126science23848301105, doi101139e85009, doi101146annurevearth36031207124326, doi105194se42152013"
}

Abstract Gondwana breakup since the Jurassic and the northward motion of India toward Eurasia were associated with formation of ocean basins and ophiolite obduction between and onto the Indian and Arabian margins. Here we reconcile marine geophysical data from preserved oceanic basins with the age and location of ophiolites in NW India and SE Arabia and seismic tomography of the mantle below the NW Indian Ocean. The North Somali and proto‐Owen basins formed due to 160–133 Ma N‐S extension between India and Somalia. Subsequent convergence destroyed part of this crust, simultaneous with the uplift of the Masirah ophiolites. Most of the preserved crust in the Owen Basin may have formed between 84 and 74 Ma, whereas the Mascarene and the Amirante basins accommodated motion between India and Madagascar/East Africa between 85 and circa 60 Ma and 75 and circa 66 Ma, respectively. Between circa 84 and 45 Ma, oblique Arabia‐India convergence culminated in ophiolite obduction onto SE Arabia and NW India and formed the Carlsberg slab in the lower mantle below the NW Indian Ocean. The NNE‐SSW oriented slab may explain the anomalous bathymetry in the NW Indian Ocean and may be considered a paleolongitudinal constraint for absolute plate motion. NW India‐Asia collision occurred at circa 20 Ma deforming the Sulaiman ranges or at 30 Ma if the Hindu Kush slab north of the Afghan block reflects intra‐Asian subduction. Our study highlights that the NW India ophiolites have no relationship with India‐Asia motion or collision but result from relative India‐Africa/Arabia motions instead.

@article{doi1010022014tc003780,
    author = "Gaina, Carmen and van Hinsbergen, Douwe J.J. and Spakman, Wim",
    title = "Tectonic interactions between India and Arabia since the Jurassic reconstructed from marine geophysics, ophiolite geology, and seismic tomography",
    year = "2015",
    journal = "Tectonics",
    abstract = "Abstract Gondwana breakup since the Jurassic and the northward motion of India toward Eurasia were associated with formation of ocean basins and ophiolite obduction between and onto the Indian and Arabian margins. Here we reconcile marine geophysical data from preserved oceanic basins with the age and location of ophiolites in NW India and SE Arabia and seismic tomography of the mantle below the NW Indian Ocean. The North Somali and proto‐Owen basins formed due to 160–133 Ma N‐S extension between India and Somalia. Subsequent convergence destroyed part of this crust, simultaneous with the uplift of the Masirah ophiolites. Most of the preserved crust in the Owen Basin may have formed between 84 and 74 Ma, whereas the Mascarene and the Amirante basins accommodated motion between India and Madagascar/East Africa between 85 and circa 60 Ma and 75 and circa 66 Ma, respectively. Between circa 84 and 45 Ma, oblique Arabia‐India convergence culminated in ophiolite obduction onto SE Arabia and NW India and formed the Carlsberg slab in the lower mantle below the NW Indian Ocean. The NNE‐SSW oriented slab may explain the anomalous bathymetry in the NW Indian Ocean and may be considered a paleolongitudinal constraint for absolute plate motion. NW India‐Asia collision occurred at circa 20 Ma deforming the Sulaiman ranges or at 30 Ma if the Hindu Kush slab north of the Afghan block reflects intra‐Asian subduction. Our study highlights that the NW India ophiolites have no relationship with India‐Asia motion or collision but result from relative India‐Africa/Arabia motions instead.",
    url = "https://doi.org/10.1002/2014tc003780",
    doi = "10.1002/2014tc003780",
    openalex = "W2153793888",
    references = "doi101016jtecto201305037, doi10108000206810903557704"
}

@article{s2d1212b4b58a8d2952944d0a68fe6ad873b0e577d,
    author = "Menges, D. and Glasmacher, U. and Hackspacher, P. and Schneider, G. and Salomon, Eric",
    title = "Long-term landscape evolution of the South Atlantic passive continental margin along the Kaoko- and Damara Belts, NW-Namibia",
    year = "2015",
    journal = "EGUGA",
    url = "https://www.semanticscholar.org/paper/d1212b4b58a8d2952944d0a68fe6ad873b0e577d",
    is_oa = "true",
    openalex = "W3027051332",
    semanticscholar_id = "d1212b4b58a8d2952944d0a68fe6ad873b0e577d"
}

Abstract We focus on the southern North Atlantic rifted margins to investigate the partitioning and propagation of deformation in hyperextended rift systems using plate kinematic modeling. The kinematic evolution of this area is well determined by oceanic magnetic anomalies after the Cretaceous normal polarity superchron. However, the rift and early seafloor spreading evolution (200–83 Ma) remains highly disputed due to contentious interpretations of the J magnetic anomaly on the Iberia‐Newfoundland conjugate margins. Recent studies highlight that the J anomaly is probably polygenic, related to polyphased magmatic events, and therefore does not correspond to an isochron. We present a new palinspastic restoration without using the J magnetic anomaly as the chron M0. We combine 3‐D gravity inversion results with local structural, stratigraphic, and geochronological constraints on the rift deformation history. The restoration of the southern North Atlantic itself is not the primary aim of the study but rather is used as a method to investigate the spatiotemporal evolution of hyperextended rift systems. We include continental microblocks that enable the partitioning of the deformation between different rift segments, which is of particular importance for the evolution of the Iberia‐Eurasia plate boundary. Our modeling highlights the following: (1) the segmentation of the Iberia‐Newfoundland rift system during continental crust thinning, (2) the northward V‐shape propagation of mantle exhumation and seafloor spreading, (3) the complex partitioning of deformation along the Iberia‐Eurasia plate boundary, and (4) a three‐plate propagation model which implies transtension.

@article{doi1010022017tc004495,
    author = "Nirrengarten, M.F.R. and Manatschal, Giänreto and Tugend, Julie and Kusznir, Nick and Sauter, Daniel",
    title = "Kinematic Evolution of the Southern North Atlantic: Implications for the Formation of Hyperextended Rift Systems",
    year = "2017",
    journal = "Tectonics",
    abstract = "Abstract We focus on the southern North Atlantic rifted margins to investigate the partitioning and propagation of deformation in hyperextended rift systems using plate kinematic modeling. The kinematic evolution of this area is well determined by oceanic magnetic anomalies after the Cretaceous normal polarity superchron. However, the rift and early seafloor spreading evolution (200–83 Ma) remains highly disputed due to contentious interpretations of the J magnetic anomaly on the Iberia‐Newfoundland conjugate margins. Recent studies highlight that the J anomaly is probably polygenic, related to polyphased magmatic events, and therefore does not correspond to an isochron. We present a new palinspastic restoration without using the J magnetic anomaly as the chron M0. We combine 3‐D gravity inversion results with local structural, stratigraphic, and geochronological constraints on the rift deformation history. The restoration of the southern North Atlantic itself is not the primary aim of the study but rather is used as a method to investigate the spatiotemporal evolution of hyperextended rift systems. We include continental microblocks that enable the partitioning of the deformation between different rift segments, which is of particular importance for the evolution of the Iberia‐Eurasia plate boundary. Our modeling highlights the following: (1) the segmentation of the Iberia‐Newfoundland rift system during continental crust thinning, (2) the northward V‐shape propagation of mantle exhumation and seafloor spreading, (3) the complex partitioning of deformation along the Iberia‐Eurasia plate boundary, and (4) a three‐plate propagation model which implies transtension.",
    url = "https://doi.org/10.1002/2017tc004495",
    doi = "10.1002/2017tc004495",
    openalex = "W2773812625",
    references = "doi1010022014tc003760, doi101002ggge20135, doi101038nature18319, doi101038ncomms5014"
}

Passive margins represent the transition from the continental to the oceanic lithosphere and, within the Wilson continent cycle, form the phase between rifting and subduction, ending in continental collision.As their name suggests, passive margins were assumed to be tectonically quiet, passively sitting on the plate after drift, until subduction would set.Around the world, two main types of continental passive margins can be found: non-elevated passive margins, with a gradual increase in elevation towards the continental interior; and elevated passive margins (EPM), with a major escarpment towards higher elevation close to the coastal plain.Research within the last decade revealed that the morphology of EPMs took form (long) after continent break-up, indicating tectonic activity at these "passive" margins.It is however still unclear what the mechanism is behind this post-breakup tectonic activity, and whether low-lying margins were once elevated (e.g. Green et al., 2018).Some studies point out the importance of inherited structures, such as faults, in the reactivation of the passive margins (e.g.Cogn et al., 2012).The Araua-West Congo orogen (AWCO) formed inside a southern embayment of the So Francisco-Congo craton (SFCC) as a result of the Brasiliano-Pan African orogeny (600-500 Ma), in a process described as nutcracker tectonics.The AWCO was thus confined by the SFCC in all directions but the south, rendering it into a unique structural setting.With the opening of the South Atlantic, due to the break-up of Gondwana during the Early Cretaceous (c.130 Ma), the AWCO was divided into two counterparts: the West Congo Belt (WCB) on the African continent (D.R. Congo, Congo Brazzaville, Gabon, Angola), and the Araua orogen in South America (Brazil) (Pedrosa-Soares et al., 2008).Both evolved into passive margins with distinctly different morphology, the Araua side being an EPM and the WCB being a low-lying margin.The apatite fission track (AFT) method is a low-temperature thermochronometer based on the spontaneous fission decay of 238U.This fission creates a damage trail (fission track) inside the crystal lattice, which is shortened at temperatures between 60C and 120C and totally annealed over 120C (Wagner & Van den haute, 1962).Fission track analysis thus provides us with information on the cooling age and time-temperature paths of samples within the upper crust.For this research we analysed samples from both sides of the South Atlantic with the AFT method.We here present results from the Brazilian margin and the first results from the D.R. Congo.The Brazilian EPM displays cooling ages ranging between 70 and 90 Ma, with long track lengths, indicating an exhumation event after break-up.This can be attributed to stress or plume-related activity.The Congolese margin however does not show this signal, but instead has ages of 100 to 130 Ma, with shorter track lengths and a larger standard deviation.This indicates a slower exhumation, which is probably related to the erosion of the rift shoulders.From the current, limited AFT dataset, no recent tectonic reactivation could be inferred for the passive margin in the D.R. Congo.

@article{s2f8100ccc687a2e12e413c9aa43ae69bf871ad8e6,
    author = "Ranst, G. V. and Tack, L. and Baudet, D. and Pedrosa-Soares, A. and Novo, T. and Grave, J.",
    title = "Tectonic evolution of the Araçuaí - West Congo orogen and the opening of the South Atlantic",
    year = "2018",
    journal = "Ghent University Academic Bibliography (Ghent University)",
    abstract = {Passive margins represent the transition from the continental to the oceanic lithosphere and, within the Wilson continent cycle, form the phase between rifting and subduction, ending in continental collision.As their name suggests, passive margins were assumed to be tectonically quiet, passively sitting on the plate after drift, until subduction would set.Around the world, two main types of continental passive margins can be found: non-elevated passive margins, with a gradual increase in elevation towards the continental interior; and elevated passive margins (EPM), with a major escarpment towards higher elevation close to the coastal plain.Research within the last decade revealed that the morphology of EPMs took form (long) after continent break-up, indicating tectonic activity at these "passive" margins.It is however still unclear what the mechanism is behind this post-breakup tectonic activity, and whether low-lying margins were once elevated (e.g. Green et al., 2018).Some studies point out the importance of inherited structures, such as faults, in the reactivation of the passive margins (e.g.Cogn et al., 2012).The Araua-West Congo orogen (AWCO) formed inside a southern embayment of the So Francisco-Congo craton (SFCC) as a result of the Brasiliano-Pan African orogeny (600-500 Ma), in a process described as nutcracker tectonics.The AWCO was thus confined by the SFCC in all directions but the south, rendering it into a unique structural setting.With the opening of the South Atlantic, due to the break-up of Gondwana during the Early Cretaceous (c.130 Ma), the AWCO was divided into two counterparts: the West Congo Belt (WCB) on the African continent (D.R. Congo, Congo Brazzaville, Gabon, Angola), and the Araua orogen in South America (Brazil) (Pedrosa-Soares et al., 2008).Both evolved into passive margins with distinctly different morphology, the Araua side being an EPM and the WCB being a low-lying margin.The apatite fission track (AFT) method is a low-temperature thermochronometer based on the spontaneous fission decay of 238U.This fission creates a damage trail (fission track) inside the crystal lattice, which is shortened at temperatures between 60C and 120C and totally annealed over 120C (Wagner \& Van den haute, 1962).Fission track analysis thus provides us with information on the cooling age and time-temperature paths of samples within the upper crust.For this research we analysed samples from both sides of the South Atlantic with the AFT method.We here present results from the Brazilian margin and the first results from the D.R. Congo.The Brazilian EPM displays cooling ages ranging between 70 and 90 Ma, with long track lengths, indicating an exhumation event after break-up.This can be attributed to stress or plume-related activity.The Congolese margin however does not show this signal, but instead has ages of 100 to 130 Ma, with shorter track lengths and a larger standard deviation.This indicates a slower exhumation, which is probably related to the erosion of the rift shoulders.From the current, limited AFT dataset, no recent tectonic reactivation could be inferred for the passive margin in the D.R. Congo.},
    url = "https://www.semanticscholar.org/paper/f8100ccc687a2e12e413c9aa43ae69bf871ad8e6",
    is_oa = "true",
    openalex = "W3009701784",
    semanticscholar_id = "f8100ccc687a2e12e413c9aa43ae69bf871ad8e6"
}

Abstract Despite the influence of other geological and geomorphological factors, chemical weathering at the Earth's surface is strongly controlled by climate. Thus, a measure of weathering intensity determined from soils or sediments should provide information about the climatic conditions associated with their formation. Available geochemical and mineralogical data on modern fluvial and marine muds from different regions of southern Africa and its Atlantic continental margin are used to review the links between sediment composition and climatic properties together with the possible causes of variance. Although river muds may not be generated exclusively in a single sedimentary cycle and erosion and weathering processes do not necessarily take place in a spatially homogeneous way, significant relationships between mineralogical and geochemical signatures of river mud and rainfall in the corresponding catchment area were recognised. Our study shows that the composition of clay is strongly influenced by climatically-driven weathering, whilst coarser mud fractions tend to be more affected by provenance, grain size, hydraulic sorting, and recycling. In the marine environment the climatic signal may be lost even in clay, because of hydraulic fractionation, authigenic mineral growth and mixing with foreign particles. Given the ubiquitous character of fluvial muds, and the easy and non-expensive methods available for separating and analysing clay fractions, their geochemical fingerprints represent a most precious source of information concerning climate. Any geochemical parameter used as a regional proxy of climate, however, still requires that the diversity of geological, geomorphological, and biological factors that affect its value are cautiously considered.

@article{doi101016jearscirev2019103039,
    author = "Dinis, Pedro A. and Garzanti, E. and Hahn, Annette and Vermeesch, P. and Cabral-Pinto, Marina",
    title = "Weathering indices as climate proxies. A step forward based on Congo and SW African river muds",
    year = "2020",
    journal = "Earth-Science Reviews",
    abstract = "Abstract Despite the influence of other geological and geomorphological factors, chemical weathering at the Earth's surface is strongly controlled by climate. Thus, a measure of weathering intensity determined from soils or sediments should provide information about the climatic conditions associated with their formation. Available geochemical and mineralogical data on modern fluvial and marine muds from different regions of southern Africa and its Atlantic continental margin are used to review the links between sediment composition and climatic properties together with the possible causes of variance. Although river muds may not be generated exclusively in a single sedimentary cycle and erosion and weathering processes do not necessarily take place in a spatially homogeneous way, significant relationships between mineralogical and geochemical signatures of river mud and rainfall in the corresponding catchment area were recognised. Our study shows that the composition of clay is strongly influenced by climatically-driven weathering, whilst coarser mud fractions tend to be more affected by provenance, grain size, hydraulic sorting, and recycling. In the marine environment the climatic signal may be lost even in clay, because of hydraulic fractionation, authigenic mineral growth and mixing with foreign particles. Given the ubiquitous character of fluvial muds, and the easy and non-expensive methods available for separating and analysing clay fractions, their geochemical fingerprints represent a most precious source of information concerning climate. Any geochemical parameter used as a regional proxy of climate, however, still requires that the diversity of geological, geomorphological, and biological factors that affect its value are cautiously considered.",
    url = "https://boa.unimib.it/bitstream/10281/292545/4/Dinis-2020-Earth\%20Sci\%20Rev-preprint.pdf",
    doi = "10.1016/j.earscirev.2019.103039",
    is_oa = "true",
    pages = "103039",
    semanticscholar_citation_count = "132",
    semanticscholar_id = "6ec0304b3856bf8294a18d21216958cd6eca3c63",
    volume = "201"
}

The 700 km-long North Atlantic Craton (NAC) in West Greenland is arguably the best exposed and most continuous section of Eo-to Neoarchaean crust on Earth. This allows a close and essential correlation between geochemical and isotopic data and primary, well-defined and well-studied geological relationships. The NAC is therefore an excellent and unsurpassed stage for the ongoing controversial discussion about uniformitarian versus non-uniformitarian crustal evolution in the Archaean. The latest research on the geochemistry, structural style, and Hf isotope geochemistry of tonalite-trondhjemite-granodiorite (TTG) complexes and their intercalated mafic to intermediate volcanic belts strongly supports previous conclusions that the NAC formed by modern-style plate tectonic processes with slab melting of wet basaltic oceanic crust in island arcs and active continental margins. New studies of the lateral tectonic convergence and collision between juvenile belts in the NAC corroborate this interpretation. Nevertheless, it has repeatedly been hypothesised that the Earth’s crust did not develop by modern-style, subhorizontal plate tectonics before 3.0 Ga, but by vertical processes such as crustal sinking and sagduction, and granitic diapirism with associated dome-and-keel structures. Many of these models are based on supposed inverted crustal density relations, with upper Archaean crust dominated by heavy mafic ridge-lavas and island arcs, and lower Archaean crust mostly consisting of felsic, supposedly buoyant TTGs. Some of them stem from older investigations of upper-crustal Archaean greenstone belts particularly in the Dharwar craton, the Slave and Superior provinces and the Barberton belt. These interpreted interactions between these upper and lower crustal rocks are based on the apparent down-dragged greenstone belts that wrap around diapiric granites. However, in the lower crustal section of the NAC, there is no evidence of any low-density granitic diapirs or heavy, downsagged or sagducted greenstone belts. Instead, the NAC contains well-exposed belts of upper crustal, arc-dominant greenstone belts imbricated and intercalated by well-defined thrusts with the protoliths of the now high-grade TTG gneisses, followed by crustal shortening mainly by folding. This shows us that the upper and lower Archaean crustal components did not interact by vertical diapirism, but by subhorizontal inter-thrusting and folding in an ambient, mainly convergent plate tectonic regime.

@article{doi103389feart2020540997,
    author = "Garde, A. and Windley, B. and Kokfelt, T. and Keulen, Nynke",
    title = "Archaean Plate Tectonics in the North Atlantic Craton of West Greenland Revealed by Well-Exposed Horizontal Crustal Tectonics, Island Arcs and Tonalite-Trondhjemite-Granodiorite Complexes",
    year = "2020",
    journal = "Frontiers in Earth Science",
    abstract = "The 700 km-long North Atlantic Craton (NAC) in West Greenland is arguably the best exposed and most continuous section of Eo-to Neoarchaean crust on Earth. This allows a close and essential correlation between geochemical and isotopic data and primary, well-defined and well-studied geological relationships. The NAC is therefore an excellent and unsurpassed stage for the ongoing controversial discussion about uniformitarian versus non-uniformitarian crustal evolution in the Archaean. The latest research on the geochemistry, structural style, and Hf isotope geochemistry of tonalite-trondhjemite-granodiorite (TTG) complexes and their intercalated mafic to intermediate volcanic belts strongly supports previous conclusions that the NAC formed by modern-style plate tectonic processes with slab melting of wet basaltic oceanic crust in island arcs and active continental margins. New studies of the lateral tectonic convergence and collision between juvenile belts in the NAC corroborate this interpretation. Nevertheless, it has repeatedly been hypothesised that the Earth’s crust did not develop by modern-style, subhorizontal plate tectonics before 3.0 Ga, but by vertical processes such as crustal sinking and sagduction, and granitic diapirism with associated dome-and-keel structures. Many of these models are based on supposed inverted crustal density relations, with upper Archaean crust dominated by heavy mafic ridge-lavas and island arcs, and lower Archaean crust mostly consisting of felsic, supposedly buoyant TTGs. Some of them stem from older investigations of upper-crustal Archaean greenstone belts particularly in the Dharwar craton, the Slave and Superior provinces and the Barberton belt. These interpreted interactions between these upper and lower crustal rocks are based on the apparent down-dragged greenstone belts that wrap around diapiric granites. However, in the lower crustal section of the NAC, there is no evidence of any low-density granitic diapirs or heavy, downsagged or sagducted greenstone belts. Instead, the NAC contains well-exposed belts of upper crustal, arc-dominant greenstone belts imbricated and intercalated by well-defined thrusts with the protoliths of the now high-grade TTG gneisses, followed by crustal shortening mainly by folding. This shows us that the upper and lower Archaean crustal components did not interact by vertical diapirism, but by subhorizontal inter-thrusting and folding in an ambient, mainly convergent plate tectonic regime.",
    url = "https://www.frontiersin.org/articles/10.3389/feart.2020.540997/pdf",
    doi = "10.3389/feart.2020.540997",
    is_oa = "true",
    semanticscholar_citation_count = "20",
    semanticscholar_id = "a00a654c9c5fa167c6bd090d48dffe3de41588c4",
    volume = "8"
}

Living turtles are characterized by extraordinarily low species diversity given their age. The clade's extensive fossil record indicates that climate and biogeography may have played important roles in determining their diversity. We investigated this hypothesis by collecting a molecular dataset for 591 individual turtles that, together, represent 80% of all turtle species, including representatives of all families and 98% of genera, and used it to jointly estimate phylogeny and divergence times. We found that the turtle tree is characterized by relatively constant diversification (speciation minus extinction) punctuated by a single threefold increase. We also found that this shift is temporally and geographically associated with newly emerged continental margins that appeared during the Eocene-Oligocene transition about 30 million years before present. In apparent contrast, the fossil record from this time period contains evidence for a major, but regional, extinction event. These seemingly discordant findings appear to be driven by a common global process: global cooling and drying at the time of the Eocene-Oligocene transition. This climatic shift led to aridification that drove extinctions in important fossil-bearing areas, while simultaneously exposing new continental margin habitat that subsequently allowed for a burst of speciation associated with these newly exploitable ecological opportunities.

@article{doi101073pnas2012215118,
    author = "Thomson, Robert C. and Spinks, Phillip Q. and Shaffer, H. Bradley",
    title = "A global phylogeny of turtles reveals a burst of climate-associated diversification on continental margins",
    year = "2021",
    journal = "Proceedings of the National Academy of Sciences",
    abstract = "Living turtles are characterized by extraordinarily low species diversity given their age. The clade's extensive fossil record indicates that climate and biogeography may have played important roles in determining their diversity. We investigated this hypothesis by collecting a molecular dataset for 591 individual turtles that, together, represent 80\% of all turtle species, including representatives of all families and 98\% of genera, and used it to jointly estimate phylogeny and divergence times. We found that the turtle tree is characterized by relatively constant diversification (speciation minus extinction) punctuated by a single threefold increase. We also found that this shift is temporally and geographically associated with newly emerged continental margins that appeared during the Eocene-Oligocene transition about 30 million years before present. In apparent contrast, the fossil record from this time period contains evidence for a major, but regional, extinction event. These seemingly discordant findings appear to be driven by a common global process: global cooling and drying at the time of the Eocene-Oligocene transition. This climatic shift led to aridification that drove extinctions in important fossil-bearing areas, while simultaneously exposing new continental margin habitat that subsequently allowed for a burst of speciation associated with these newly exploitable ecological opportunities.",
    url = "https://doi.org/10.1073/pnas.2012215118",
    doi = "10.1073/pnas.2012215118",
    openalex = "W3127436575",
    references = "doi101016jympev201705008, doi1010292018gc007584, doi10166612149"
}

The Lower Congo region encompasses the South Atlantic passive margin of the Democratic Republic of Congo (CentralAfrica).ItishosttothelowermostcourseoftheCongoRiver,cuttingthroughtheCentralAfricanAtlantic Swell(CAAS).Theregionisunderlainbylitho-structuralunitsofthePan-AfricanWestCongoBelt,whichconsists ofdifferenttectono-metamorphicdomains.ThePrecambrianbasementiscoveredtothewestbymarinedeposits of the South Atlantic Ocean and to the east by continental deposits of the Congo Basin. In this study we aim to constrainthetiming ofupliftandexhumationoftheCAASby usingapatite fi ssion track(AFT)thermochronology in combination with an updated overview of the geology and geomorphology of the Lower Congo region. AFT agesvarywidely between108and 312 Ma.Shorttracklengths (11 – 12 μ m)and broad, complextrack lengthdis-tributions indicate mixed ages between multiple thermal events. We derive the timing of exhumation from in- verse thermal history models, that show that the Lower Congo region experienced a fi rst exhumation event before Gondwana breakup during the Carboniferous to Middle Jurassic. This event is probably related to com- pressive forces at the boundaries of Gondwana. Both rifting and subsequent opening of the South Atlantic Ocean do not seem to have had a pronounced effect on the CAAS region. During the Late Cretaceous to Palaeogene, a slight reheating is suggested and could be due to subsidence and consequential modest reburial of the Lower Congo rocks. A second phase of exhumation initiated around the Palaeogene – Neogene and eventually emplaced the sampled rocks at surface temperatures. The multi-phased differential denudation results from reactivation of fault-bounded tectono-metamorphic blocks of the Precambrian basement, controlled by the combination of two systems offaults relatedtotheCretaceous South AtlanticOcean opening andPan-African orogeny respectively.Dif-ferential denudation of the Lower Congo region is also well-marked by independent qualitative indicators of the present-day geomorphology including distinct knickpoints and steep valleys along the course of the Lower Congo River, reworking of erosion surfaces and associated laterite crust and contrasting karst morphology. © 2021 Elsevier B.V. All rights reserved.

@article{doi101016jgeomorph2021108067,
    author = "Ranst, G. Van and Fonseca, A. and Tack, L. and Delvaux, D. and Baudet, D. and Kitambala, N. and Pay, A. and Grave, J. De",
    title = "Exhumation of the passive margin of the DR Congo during pre- and post- Gondwana breakup: Evidence from low-temperature thermochronology, geology and geomorphology",
    year = "2022",
    journal = "Geomorphology",
    abstract = "The Lower Congo region encompasses the South Atlantic passive margin of the Democratic Republic of Congo (CentralAfrica).ItishosttothelowermostcourseoftheCongoRiver,cuttingthroughtheCentralAfricanAtlantic Swell(CAAS).Theregionisunderlainbylitho-structuralunitsofthePan-AfricanWestCongoBelt,whichconsists ofdifferenttectono-metamorphicdomains.ThePrecambrianbasementiscoveredtothewestbymarinedeposits of the South Atlantic Ocean and to the east by continental deposits of the Congo Basin. In this study we aim to constrainthetiming ofupliftandexhumationoftheCAASby usingapatite fi ssion track(AFT)thermochronology in combination with an updated overview of the geology and geomorphology of the Lower Congo region. AFT agesvarywidely between108and 312 Ma.Shorttracklengths (11 – 12 μ m)and broad, complextrack lengthdis-tributions indicate mixed ages between multiple thermal events. We derive the timing of exhumation from in- verse thermal history models, that show that the Lower Congo region experienced a fi rst exhumation event before Gondwana breakup during the Carboniferous to Middle Jurassic. This event is probably related to com- pressive forces at the boundaries of Gondwana. Both rifting and subsequent opening of the South Atlantic Ocean do not seem to have had a pronounced effect on the CAAS region. During the Late Cretaceous to Palaeogene, a slight reheating is suggested and could be due to subsidence and consequential modest reburial of the Lower Congo rocks. A second phase of exhumation initiated around the Palaeogene – Neogene and eventually emplaced the sampled rocks at surface temperatures. The multi-phased differential denudation results from reactivation of fault-bounded tectono-metamorphic blocks of the Precambrian basement, controlled by the combination of two systems offaults relatedtotheCretaceous South AtlanticOcean opening andPan-African orogeny respectively.Dif-ferential denudation of the Lower Congo region is also well-marked by independent qualitative indicators of the present-day geomorphology including distinct knickpoints and steep valleys along the course of the Lower Congo River, reworking of erosion surfaces and associated laterite crust and contrasting karst morphology. © 2021 Elsevier B.V. All rights reserved.",
    url = "https://www.semanticscholar.org/paper/84708bd63584daa448e285e330c1b7cdce6dd716",
    doi = "10.1016/j.geomorph.2021.108067",
    is_oa = "true",
    pages = "108067",
    semanticscholar_citation_count = "5",
    semanticscholar_id = "84708bd63584daa448e285e330c1b7cdce6dd716",
    volume = "398"
}

The last phase of Atlantic Ocean opening involved Late Albian rifting and separation of Africa and South America along the Equatorial Atlantic. Prior to the Albian, initiation and northward propagation of sea-floor spreading caused rotation of the South American plate and formation of two main rift systems in NE Brazil and West Africa: • The Northeast Brazilian Rift System, consisting of the Reconcavo-Tucano-Jatoba (RTJ); Sergipe Alagoas/Gabon (SAG) and • Cariri-Potiguar (CP) rifts in Brazil and the WestCentral African Rift System (WCARS) in Africa. The Brazilian basins developed inside and around the Borborema Province, a key Proterozoic structure that controlled spatial and temporal differences between these rift systems. Our analysis of a new compilation of onshore and offshore faults of the Equatorial Atlantic led us to the conclusion that the segment bound by the Kribi and Bode Verde fracture zones south of Borborema acted as a link between intracontinental rifting to the north and late rifting stages in the Central Atlantic. During the Albian, this region acted as a ̈buffer zone, ̈ balancing, kinematically, in time and space, dextral strike slip rifting in the Equatorial branch, with simultaneous sea-floor spreading in the Central segment. In this article we tie sequence stratigraphic rift sequences to plate kinematic changes described in our new plate model. Attempts to consider the thermal and tectonic evolution of the Central Salt Basins of the South Atlantic as an analog for the Equatorial Margin may lead to wrong predictions in hydrocarbon exploration. The differences in the development of these segments may explain the asymmetry in the distribution of oil and gas reserves along the South Atlantic Margin. Introduction Onshore studies of Northern Brazilian basins (Amazonas, Foz do Amazonas, Marajo, Grajau, Sao Luis, and Ilha Nova basins) by Soares et al. (2008, 2011) dated rifting phases from Late Triassic to Albian. The structural styles of the basins were interpreted to be controlled by an interplay between inherited geology during the early rifting stage and by readjustment of the plates at the initiation of the sea-floor spreading (Matos et al., 2017; Krueger 2012; Krueger et al. (2014, 2015a, 2015b). Offshore basins along the Brazilian Equatorial Atlantic margin were previously described as contemporary strike-slip basins, separated by the Romanche Fracture Zone and the northern and southern branches of Sao Paulo Fracture Zone (FZ). We integrated all newly published observations along the margin into a New Plate Tectonic Model, which predicts diachronous development and fits the data, reducing misfit errors along the South American and African margins. Methodology This work consists of a compilation of multiple datasets that include: 2D seismic mapping (Krueger, 2012), digitized and edited onshore faults on new tectonic maps of South America (Cordani et al., 2016) and Africa (Meghraoui, et al., 2016), combined with offshore maps from Matos (2000) for South America and from Casey (2014) for Africa. Using our combined seismic data interpretation (Matos, 2000; Krueger, 2012; Casey, 2014) aided by free-air gravity interpretation (Sandwell et al., 2014) (Figure 1) and modeling (Watts and Fairhead (1999), we mapped the limit of oceanic crust on both sides of the Atlantic. Our interpretation was used in the updates for the UTIG PLATES model. We used PaleoGIS software from the Rothwell Group L.P. and the UTIG PLATES Model to restore basement structures and faults from Krueger (2012) together with those from Matos (2004) and Casey (2014) and new structural interpretation of the faults onshore of South America to build the paleogeographic maps for the Lower to Mid-Cretaceous. Proterozoic Heritage West Gondwana was a collage of diversified Tonian terranes (1000 – 900 Ma) amalgamated during diachronic Brasiliano/Pan African orogenies (ca. 800 – 500 Ma, Brito Neves at al., 2014). The Trans-Brazilian terranes (TBL) is a complex net of Neoproterozoic mobile belts of Neoproterozoic age, formed as the Brazilian and African cratons moved and collided with the Congo Craton. (Brito Neves et al., 2014). This event is called Brasiliano or PanAfrican. The Brasiliano/Pan African tectonic event produced the main structures of West Gondwana: 1)-The 3000 km-long Trans–Saharan (TSL) lineament and 2)-its southward continuation, the Transbrasiliano Lineament (TBL, from NW Ceará, in Brazil, all the way to Argentina), also a 3000-km-long shear zone (Figure 2). The TSL borders the West African Craton, with associated arcrelated Neoproterozoic rocks, ophiolites, and accretionary prisms. The TBL separates the Amazon Craton (Amazonian or pre-Brasiliano domain) from the Brasiliano terranes (Brito Neves at al., 2014). Linked with the TBL, the Borborema Province is one important Neoproterozoic cratonic nuclei, formed by a complex framework of orogenic branching system. We named this large polycyclic NNE shear belt in Brazil, and its continuity in Africa, as the Borborema Horsetail Splay (BHS) (Fig. 2). The Transversal Zone (TZ) is located in the central domain of the Borborema province (BHS) between Patos (LPT) and Pernambuco (LPE) lineaments; The LPT has been recognized as a continental transform linking a recognized magmatic arc at the northern portion of the TZ (ca. 635-580 Ma), a product of a Mesoand Neoproterozoic plate-tectonic accretionary processes (Brito Neves at. al (2016), The eastward extension of the TZ, is represented by the Central African belt or shear zone (CASZ), another Neoproterozoic shear zone, a product of a continental collision during which the Nigerian Shield was thrusted onto the Congo Craton. The Orthogonal Zone (OZ) exploited Neoproterozoic zones of weakness and was active during the Early Cretaceous as initiation and northward propagation of sea-floor spreading caused rotation of the South American plate. To avoid confusion between the Proterozoic kinematic behavior of this Transversal Zone and Cretaceous, here we refer to the Cretaceous kinematic segment as “Orthogonal Zone”. The OZ behaved as a large-scale dextral transfer zone, balancing rift development between the future Equatorial and Central Atlantic branches of the South Atlantic. Two main rift systems in NE Brazil and West Africa formed, exploiting these zones of weakness: 1)in Brazil, the Northeast Brazilian Rift System, consisting of the Reconcavo-Tucano-Jatoba rifts (RTJ); Sergipe Alagoas/Gabon (SAG) and Cariri-Potiguar (CP) rift valleys (Magnavita, 1992, Matos, 1999, Destro et al., 2003; Burke et al. 2003, Brito Neves and Cordani, 1991), and the West and Central African Rift System (WCARS); 2)in Africa, as documented by Brown and Fairhead (1983), Fairhead et al. (2012, 2013), Fairhead and Binks (1991), Fairhead and Green (1989), Hargue et al. (1992), Yandoka et al. (2014), and Yassin et al., (2017). Both rift systems aborted, and final rifting took place along the present day continental margins. This switch was driven by the presence of lithospheric keels under the Nigerian and Borborema shields, not allowing rifting to propagate through them. The last phase of Atlantic Ocean opening finally took place in Late Albian. Opening of the Equatorial South Atlantic Initiation and northward propagation of sea-floor spreading in South Atlantic caused rotation of the South American plate with respect to Africa and formation of the two main rift systems in NE Brazil and West Africa. Oblique deformation requires less strain and as much as two times less force in order to reach the brittle yield stress (Brune et al., 2012; Brune and Autin, 2013; Heine and Brune, 2014). Once yield is reached, hot asthenospheric upwelling and friction softening promote extensive lithospheric weakening (Heine and Brune, 2014). Basins in and around the Borborema Province records pre-rift and post-rift stages from 145 to 100 Ma. Strike-slip movements in the Equatorial Margin, kinematically linked to the final rifting stages in the Central South Atlantic segment, began during the Aptian (Matos et al., 2017). Therefore, from Aptian to Albian time (120 Ma to 110 Ma) the South Atlantic path of continental rifting moved around the Borborema Province and developed into a system of oblique and narrow rifted basins floored by oceanic crust. Rifts exhibit episodes of transpression and transtension during this phase of deformation controlled primarily by the degree of obliquity of each basin to the plate motion vector (Krueger, 2012). Oceanic crust emplacement in each basin was diachronous. South of the Romanche FZ, outboard of Rio Grande do Norte and Nigeria, oceanic crust began to form around 112 Ma, while north of the Romanche continent-ocean transform fault, oceanic crust emplacement occurred around 110 Ma. Oceanic crust formed outboard of the southeast corner of the Demerara Plateau in French Guiana and Guinea at 116 Ma, at Amapa and Sierra Leone at 114 Ma, and in northern part of Para and Liberia; Piaui, Maranhao, Ivory Coast, and Ghana at 110 Ma (Figure 3). Concluding Remarks The Borborema Province Proterozoic element with a cratonic core and the frame of adjacent Pan African fold belts, (Figure 2) acted as an obstacle to northward-propagating rifting of the South Atlantic, thereby delaying rifting and forcing South Atlantic opening to the east, following zones of weakness on the orthogonal zone. We define the term “buffer zone” as a region where rifting was delayed or slowed as rifting followed a path of thinner continental lithosphere, surrounding lithospheric keels. Once the driving forces from the divergent plate movements (from the evolving Central and South Atlantic) reached a critical point, a lithospheric cutting shear zone developed around the Borborema and Nigerian cratons, defining the silhouette of the future Equatorial Atlantic. Because of the Proterozoic heritage, the South Atlantic Equatorial margins developed intrincate NW-SE geometries, which combined with the

@article{doi10130630577krueger2018,
    author = "Krueger, A. and Norton, I. and Casey, E. and Matos, R. D. and Murphy, M.",
    title = "Influence of Proterozoic Heritage on Development of Rift Segments in the Equatorial Atlantic",
    year = "2023",
    journal = "2018 AAPG Annual Convention \& Exhibition",
    booktitle = "2018 AAPG Annual Convention \& Exhibition",
    abstract = "The last phase of Atlantic Ocean opening involved Late Albian rifting and separation of Africa and South America along the Equatorial Atlantic. Prior to the Albian, initiation and northward propagation of sea-floor spreading caused rotation of the South American plate and formation of two main rift systems in NE Brazil and West Africa: • The Northeast Brazilian Rift System, consisting of the Reconcavo-Tucano-Jatoba (RTJ); Sergipe Alagoas/Gabon (SAG) and • Cariri-Potiguar (CP) rifts in Brazil and the WestCentral African Rift System (WCARS) in Africa. The Brazilian basins developed inside and around the Borborema Province, a key Proterozoic structure that controlled spatial and temporal differences between these rift systems. Our analysis of a new compilation of onshore and offshore faults of the Equatorial Atlantic led us to the conclusion that the segment bound by the Kribi and Bode Verde fracture zones south of Borborema acted as a link between intracontinental rifting to the north and late rifting stages in the Central Atlantic. During the Albian, this region acted as a ̈buffer zone, ̈ balancing, kinematically, in time and space, dextral strike slip rifting in the Equatorial branch, with simultaneous sea-floor spreading in the Central segment. In this article we tie sequence stratigraphic rift sequences to plate kinematic changes described in our new plate model. Attempts to consider the thermal and tectonic evolution of the Central Salt Basins of the South Atlantic as an analog for the Equatorial Margin may lead to wrong predictions in hydrocarbon exploration. The differences in the development of these segments may explain the asymmetry in the distribution of oil and gas reserves along the South Atlantic Margin. Introduction Onshore studies of Northern Brazilian basins (Amazonas, Foz do Amazonas, Marajo, Grajau, Sao Luis, and Ilha Nova basins) by Soares et al. (2008, 2011) dated rifting phases from Late Triassic to Albian. The structural styles of the basins were interpreted to be controlled by an interplay between inherited geology during the early rifting stage and by readjustment of the plates at the initiation of the sea-floor spreading (Matos et al., 2017; Krueger 2012; Krueger et al. (2014, 2015a, 2015b). Offshore basins along the Brazilian Equatorial Atlantic margin were previously described as contemporary strike-slip basins, separated by the Romanche Fracture Zone and the northern and southern branches of Sao Paulo Fracture Zone (FZ). We integrated all newly published observations along the margin into a New Plate Tectonic Model, which predicts diachronous development and fits the data, reducing misfit errors along the South American and African margins. Methodology This work consists of a compilation of multiple datasets that include: 2D seismic mapping (Krueger, 2012), digitized and edited onshore faults on new tectonic maps of South America (Cordani et al., 2016) and Africa (Meghraoui, et al., 2016), combined with offshore maps from Matos (2000) for South America and from Casey (2014) for Africa. Using our combined seismic data interpretation (Matos, 2000; Krueger, 2012; Casey, 2014) aided by free-air gravity interpretation (Sandwell et al., 2014) (Figure 1) and modeling (Watts and Fairhead (1999), we mapped the limit of oceanic crust on both sides of the Atlantic. Our interpretation was used in the updates for the UTIG PLATES model. We used PaleoGIS software from the Rothwell Group L.P. and the UTIG PLATES Model to restore basement structures and faults from Krueger (2012) together with those from Matos (2004) and Casey (2014) and new structural interpretation of the faults onshore of South America to build the paleogeographic maps for the Lower to Mid-Cretaceous. Proterozoic Heritage West Gondwana was a collage of diversified Tonian terranes (1000 – 900 Ma) amalgamated during diachronic Brasiliano/Pan African orogenies (ca. 800 – 500 Ma, Brito Neves at al., 2014). The Trans-Brazilian terranes (TBL) is a complex net of Neoproterozoic mobile belts of Neoproterozoic age, formed as the Brazilian and African cratons moved and collided with the Congo Craton. (Brito Neves et al., 2014). This event is called Brasiliano or PanAfrican. The Brasiliano/Pan African tectonic event produced the main structures of West Gondwana: 1)-The 3000 km-long Trans–Saharan (TSL) lineament and 2)-its southward continuation, the Transbrasiliano Lineament (TBL, from NW Ceará, in Brazil, all the way to Argentina), also a 3000-km-long shear zone (Figure 2). The TSL borders the West African Craton, with associated arcrelated Neoproterozoic rocks, ophiolites, and accretionary prisms. The TBL separates the Amazon Craton (Amazonian or pre-Brasiliano domain) from the Brasiliano terranes (Brito Neves at al., 2014). Linked with the TBL, the Borborema Province is one important Neoproterozoic cratonic nuclei, formed by a complex framework of orogenic branching system. We named this large polycyclic NNE shear belt in Brazil, and its continuity in Africa, as the Borborema Horsetail Splay (BHS) (Fig. 2). The Transversal Zone (TZ) is located in the central domain of the Borborema province (BHS) between Patos (LPT) and Pernambuco (LPE) lineaments; The LPT has been recognized as a continental transform linking a recognized magmatic arc at the northern portion of the TZ (ca. 635-580 Ma), a product of a Mesoand Neoproterozoic plate-tectonic accretionary processes (Brito Neves at. al (2016), The eastward extension of the TZ, is represented by the Central African belt or shear zone (CASZ), another Neoproterozoic shear zone, a product of a continental collision during which the Nigerian Shield was thrusted onto the Congo Craton. The Orthogonal Zone (OZ) exploited Neoproterozoic zones of weakness and was active during the Early Cretaceous as initiation and northward propagation of sea-floor spreading caused rotation of the South American plate. To avoid confusion between the Proterozoic kinematic behavior of this Transversal Zone and Cretaceous, here we refer to the Cretaceous kinematic segment as “Orthogonal Zone”. The OZ behaved as a large-scale dextral transfer zone, balancing rift development between the future Equatorial and Central Atlantic branches of the South Atlantic. Two main rift systems in NE Brazil and West Africa formed, exploiting these zones of weakness: 1)in Brazil, the Northeast Brazilian Rift System, consisting of the Reconcavo-Tucano-Jatoba rifts (RTJ); Sergipe Alagoas/Gabon (SAG) and Cariri-Potiguar (CP) rift valleys (Magnavita, 1992, Matos, 1999, Destro et al., 2003; Burke et al. 2003, Brito Neves and Cordani, 1991), and the West and Central African Rift System (WCARS); 2)in Africa, as documented by Brown and Fairhead (1983), Fairhead et al. (2012, 2013), Fairhead and Binks (1991), Fairhead and Green (1989), Hargue et al. (1992), Yandoka et al. (2014), and Yassin et al., (2017). Both rift systems aborted, and final rifting took place along the present day continental margins. This switch was driven by the presence of lithospheric keels under the Nigerian and Borborema shields, not allowing rifting to propagate through them. The last phase of Atlantic Ocean opening finally took place in Late Albian. Opening of the Equatorial South Atlantic Initiation and northward propagation of sea-floor spreading in South Atlantic caused rotation of the South American plate with respect to Africa and formation of the two main rift systems in NE Brazil and West Africa. Oblique deformation requires less strain and as much as two times less force in order to reach the brittle yield stress (Brune et al., 2012; Brune and Autin, 2013; Heine and Brune, 2014). Once yield is reached, hot asthenospheric upwelling and friction softening promote extensive lithospheric weakening (Heine and Brune, 2014). Basins in and around the Borborema Province records pre-rift and post-rift stages from 145 to 100 Ma. Strike-slip movements in the Equatorial Margin, kinematically linked to the final rifting stages in the Central South Atlantic segment, began during the Aptian (Matos et al., 2017). Therefore, from Aptian to Albian time (120 Ma to 110 Ma) the South Atlantic path of continental rifting moved around the Borborema Province and developed into a system of oblique and narrow rifted basins floored by oceanic crust. Rifts exhibit episodes of transpression and transtension during this phase of deformation controlled primarily by the degree of obliquity of each basin to the plate motion vector (Krueger, 2012). Oceanic crust emplacement in each basin was diachronous. South of the Romanche FZ, outboard of Rio Grande do Norte and Nigeria, oceanic crust began to form around 112 Ma, while north of the Romanche continent-ocean transform fault, oceanic crust emplacement occurred around 110 Ma. Oceanic crust formed outboard of the southeast corner of the Demerara Plateau in French Guiana and Guinea at 116 Ma, at Amapa and Sierra Leone at 114 Ma, and in northern part of Para and Liberia; Piaui, Maranhao, Ivory Coast, and Ghana at 110 Ma (Figure 3). Concluding Remarks The Borborema Province Proterozoic element with a cratonic core and the frame of adjacent Pan African fold belts, (Figure 2) acted as an obstacle to northward-propagating rifting of the South Atlantic, thereby delaying rifting and forcing South Atlantic opening to the east, following zones of weakness on the orthogonal zone. We define the term “buffer zone” as a region where rifting was delayed or slowed as rifting followed a path of thinner continental lithosphere, surrounding lithospheric keels. Once the driving forces from the divergent plate movements (from the evolving Central and South Atlantic) reached a critical point, a lithospheric cutting shear zone developed around the Borborema and Nigerian cratons, defining the silhouette of the future Equatorial Atlantic. Because of the Proterozoic heritage, the South Atlantic Equatorial margins developed intrincate NW-SE geometries, which combined with the",
    url = "https://www.semanticscholar.org/paper/30951d78258a0d084139931ee5b9285d54988607",
    doi = "10.1306/30577krueger2018",
    is_oa = "true",
    semanticscholar_id = "30951d78258a0d084139931ee5b9285d54988607"
}