Electrofacies

This paper presents a summary of the history, geology, and development of the Slick-Wilcox field, DeWitt and Goliad counties, Texas, from its discovery until April, 1947. The Slick-Wilcox field is located on the DeWitt-Goliad County line southeast of the town of Nordheim. The surface is underlain by southeasterly dipping Tertiary beds. Oil was discovered in the “Pettus” sand in the Cockfield member of the Yegua formation in December, 1930. Discovery was the result of surface structural mapping. Shallow “Pettus” production was largely abandoned after 1937, and deeper oil was produced from the third sand of the upper Carrizo-Wilcox section in May, 1943. Location for the well which discovered the deeper producing sand was made from subsurface information gained from geophysical prospecting. The accumulation of oil occurs in a faulted dome. The oil is trapped against a normal fault upthrown on the north. The oil is being produced by a combination of the forces resulting from a natural water drive and an expanding gas cap. There are 48 producing oil wells in the field. By the end of March, 1947, the field has produced 4,339,599 barrels of oil from the producing zone in the Carrizo-Wilcox. The original recoverable reserve is estimated at 20,000,000 barrels of oil.

@article{sebring1948slickwilcox,
    author = "Sebring, Louie",
    title = "Slick-Wilcox Field, Dewitt and Goliad Counties, Texas",
    year = "1948",
    journal = "AAPG Bulletin",
    abstract = "This paper presents a summary of the history, geology, and development of the Slick-Wilcox field, DeWitt and Goliad counties, Texas, from its discovery until April, 1947. The Slick-Wilcox field is located on the DeWitt-Goliad County line southeast of the town of Nordheim. The surface is underlain by southeasterly dipping Tertiary beds. Oil was discovered in the “Pettus” sand in the Cockfield member of the Yegua formation in December, 1930. Discovery was the result of surface structural mapping. Shallow “Pettus” production was largely abandoned after 1937, and deeper oil was produced from the third sand of the upper Carrizo-Wilcox section in May, 1943. Location for the well which discovered the deeper producing sand was made from subsurface information gained from geophysical prospecting. The accumulation of oil occurs in a faulted dome. The oil is trapped against a normal fault upthrown on the north. The oil is being produced by a combination of the forces resulting from a natural water drive and an expanding gas cap. There are 48 producing oil wells in the field. By the end of March, 1947, the field has produced 4,339,599 barrels of oil from the producing zone in the Carrizo-Wilcox. The original recoverable reserve is estimated at 20,000,000 barrels of oil.",
    url = "https://doi.org/10.1306/3d933af1-16b1-11d7-8645000102c1865d",
    doi = "10.1306/3d933af1-16b1-11d7-8645000102c1865d",
    number = "2",
    pages = "228-251",
    volume = "32"
}

ABSTRACT The Late Quaternary Niger delta in the Gulf of Guinea is a large, arcuate “classical” delta associated with marginal estuary and barrier island-lagoon complexes. The Late Quaternary deltaic lens (minimum volume 900 cubic kilometers) is the latest accretion within the Nigerian Coastal Plain geosyncline. Sediment originating in a vast and geologically complex hinterland is dispersed through the delta by river, tidal, wave, and ocean currents. Delta growth began during the Late Wisconsin lowstand of the sea when the rivers entrenched the continental shelf to reach mouths above submarine canyons at the shelf edge. The oldest stratigraphical unit of the Late Quaternary deltaic pile is a strand plain sand (Older Sands) representing a marine transgression into the hinterland. Later, in the Holocene, when sea-level became relatively stable, regressive advance across the sands of concentrically arranged delta environments gave rise to the Younger Suite, the uppermost stratigraphical formation in the deltaic lens. Lithofacies of this suite grade upward from open shelf clays, through pro-delta slope layered clays, silts, and sands, to well-bedded sands formed on the delta-front platform, river mouth bars, and beaches. Behind beach ridge barrier islands fringing the visible part of the delta occur tidal mangrove swamps in which organic-rich sands and silts are being deposited. Cross-stratified river bar sands are accumulating in association with top-stratum silts and clays in the delta floodplain environment. The sedimentary framework of the Late Quaternary Niger delta is based on essentially concentric facies elements, as in many other “classical” deltas, rather than on radial elements as in the Mississippi birdfoot delta.

@article{doi101306a663363a16c011d78645000102c1865d,
    author = "Allen, J.R.L.",
    title = "Late Quaternary Niger Delta, and Adjacent Areas: Sedimentary Environments and Lithofacies",
    year = "1965",
    journal = "AAPG Bulletin",
    abstract = "ABSTRACT The Late Quaternary Niger delta in the Gulf of Guinea is a large, arcuate “classical” delta associated with marginal estuary and barrier island-lagoon complexes. The Late Quaternary deltaic lens (minimum volume 900 cubic kilometers) is the latest accretion within the Nigerian Coastal Plain geosyncline. Sediment originating in a vast and geologically complex hinterland is dispersed through the delta by river, tidal, wave, and ocean currents. Delta growth began during the Late Wisconsin lowstand of the sea when the rivers entrenched the continental shelf to reach mouths above submarine canyons at the shelf edge. The oldest stratigraphical unit of the Late Quaternary deltaic pile is a strand plain sand (Older Sands) representing a marine transgression into the hinterland. Later, in the Holocene, when sea-level became relatively stable, regressive advance across the sands of concentrically arranged delta environments gave rise to the Younger Suite, the uppermost stratigraphical formation in the deltaic lens. Lithofacies of this suite grade upward from open shelf clays, through pro-delta slope layered clays, silts, and sands, to well-bedded sands formed on the delta-front platform, river mouth bars, and beaches. Behind beach ridge barrier islands fringing the visible part of the delta occur tidal mangrove swamps in which organic-rich sands and silts are being deposited. Cross-stratified river bar sands are accumulating in association with top-stratum silts and clays in the delta floodplain environment. The sedimentary framework of the Late Quaternary Niger delta is based on essentially concentric facies elements, as in many other “classical” deltas, rather than on radial elements as in the Mississippi birdfoot delta.",
    url = "https://doi.org/10.1306/a663363a-16c0-11d7-8645000102c1865d",
    doi = "10.1306/a663363a-16c0-11d7-8645000102c1865d",
    openalex = "W2006909095",
    references = "doi1013065ceae5bf16bb11d78645000102c1865d"
}

In the Woodbend Group of central Alberta, shales of the Ireton Formation occupy the basinal areas between the Leduc reefs. Within the shales are thin limestone beds which can be traced as electric-log markers over large areas. These markers probably approximate time lines, and they show a distinct westward divergence from the Ireton-Nisku contact. Their stratigraphic behavior has allowed subdivision of the Ireton Formation into rocks typical of the “three critical environments of deposition” established by Rich (1951a). Studies of cores and well cuttings corroborated the conclusions about environment which were reached by the study of the stratigraphic behavior of the marker beds. The lithologies described by Rich for the unda, clino, and fondo environments are present in the Ireton. The sediments of the Ireton are composed of terrigenous clay transported over a shelf area in the east, combined with fine carbonate derived from the scattered reefs throughout the area. The carbonates of the Upper Ireton are indigenous to the shelf environment. The pattern of shifting environments indicates that the inter-reef area was filled progressively from east to west. The paleogeography of a restricted area during Woodbend time has been deduced in a generalized manner by the application of Rich’s concepts.

@article{olivers1965depositional,
    author = "OLIVERS, T. A. and COWPER, N. W.",
    title = "Depositional Environments of Ireton Formation, Central Alberta",
    year = "1965",
    journal = "AAPG Bulletin",
    abstract = "In the Woodbend Group of central Alberta, shales of the Ireton Formation occupy the basinal areas between the Leduc reefs. Within the shales are thin limestone beds which can be traced as electric-log markers over large areas. These markers probably approximate time lines, and they show a distinct westward divergence from the Ireton-Nisku contact. Their stratigraphic behavior has allowed subdivision of the Ireton Formation into rocks typical of the “three critical environments of deposition” established by Rich (1951a). Studies of cores and well cuttings corroborated the conclusions about environment which were reached by the study of the stratigraphic behavior of the marker beds. The lithologies described by Rich for the unda, clino, and fondo environments are present in the Ireton. The sediments of the Ireton are composed of terrigenous clay transported over a shelf area in the east, combined with fine carbonate derived from the scattered reefs throughout the area. The carbonates of the Upper Ireton are indigenous to the shelf environment. The pattern of shifting environments indicates that the inter-reef area was filled progressively from east to west. The paleogeography of a restricted area during Woodbend time has been deduced in a generalized manner by the application of Rich’s concepts.",
    url = "https://doi.org/10.1306/a6633722-16c0-11d7-8645000102c1865d",
    doi = "10.1306/a6633722-16c0-11d7-8645000102c1865d",
    number = "9",
    pages = "1410-1425",
    volume = "49"
}

ABSTRACT The New Albany Shale in Indiana is dominantly brownish-black, carbon-rich, quartzose, dolomitic, pyritic shale that was deposited during late Middle Devonian, Late Devonian, and Early Mississippian times. Greenish-gray carbon-poor shale, dolomite, and sandstone also are present and permit stratigraphic subdivision of the formation. In descending order, the Clegg Creek Member, Camp Run Member, Morgan Trail Member, Selmier Member, and Blocher Member are named and described in this report in the southern Indiana outcrop area. The lower two members are widely traceable in the subsurface, but the upper three members are not differentiated in the subsurface. The Antrim Shale, Ellsworth Shale, and Sunbury Shale, together equivalent to the New Albany, are recognized in the Michigan basin part of northern Indiana. The Ellsworth Shale can be traced into the northern part of the Illinois basin in Indiana, where it is recognized as a member of the New Albany Shale. The New Albany Shale was deposited in a widespread inland sea. The sea was characterized by quiet water that probably was deep in places. The organic matter was derived from a floating mat of algae and accumulated under reducing bottom conditions that were inimical to benthonic faunas. Breaks in the algal mat or its periodic disruption allowed carbon-poor greenish-gray shale, with benthonic faunas, to be deposited. The algae also may have induced the formation of dolomite by changing the hydrogen-ion concentration of the water.

@article{doi1013065d25c4ab16c111d78645000102c1865d,
    author = "Lineback, Jerry Alvin",
    title = "Subdivisions and Depositional Environments Of New Albany Shale (Devonian-Mississippian) in Indiana",
    year = "1968",
    journal = "AAPG Bulletin",
    abstract = "ABSTRACT The New Albany Shale in Indiana is dominantly brownish-black, carbon-rich, quartzose, dolomitic, pyritic shale that was deposited during late Middle Devonian, Late Devonian, and Early Mississippian times. Greenish-gray carbon-poor shale, dolomite, and sandstone also are present and permit stratigraphic subdivision of the formation. In descending order, the Clegg Creek Member, Camp Run Member, Morgan Trail Member, Selmier Member, and Blocher Member are named and described in this report in the southern Indiana outcrop area. The lower two members are widely traceable in the subsurface, but the upper three members are not differentiated in the subsurface. The Antrim Shale, Ellsworth Shale, and Sunbury Shale, together equivalent to the New Albany, are recognized in the Michigan basin part of northern Indiana. The Ellsworth Shale can be traced into the northern part of the Illinois basin in Indiana, where it is recognized as a member of the New Albany Shale. The New Albany Shale was deposited in a widespread inland sea. The sea was characterized by quiet water that probably was deep in places. The organic matter was derived from a floating mat of algae and accumulated under reducing bottom conditions that were inimical to benthonic faunas. Breaks in the algal mat or its periodic disruption allowed carbon-poor greenish-gray shale, with benthonic faunas, to be deposited. The algae also may have induced the formation of dolomite by changing the hydrogen-ion concentration of the water.",
    url = "https://doi.org/10.1306/5d25c4ab-16c1-11d7-8645000102c1865d",
    doi = "10.1306/5d25c4ab-16c1-11d7-8645000102c1865d",
    openalex = "W2127402307",
    references = "doi1013063d93431c16b111d78645000102c1865d"
}

Abstract Detailed correlation of electric-log resistivity patterns that result from variations in bentonite content of marine shale and siltstone reveals the presence of inclined time-stratigraphic units within the post-Turonian, marine Late Cretaceous section of Wyoming. Similar units have been recognized in rocks of the Permo-Pennsylvanian of Texas, the Devonian of Alberta, and the Mississippian of Illinois, and are attributed to submarine depositional topography. This interpretation, applied to the Late Cretaceous section of Wyoming, divides the epicontinental marine section into three major environments: shelf, slope, and basin. The inclined time-stratigraphic units were deposited on the slope, whereas thinner, more flat-lying units were deposited on the shelf and in the basin. Three examples demonstrate the wide areal distribution and the almost continuous presence of significant submarine topography in at least part of Wyoming during post-Turonian Late Cretaceous time. The first example, from the lower Cody Shale of the southeastern Big Horn basin, is used to introduce the concepts involved and methods of correlation and mapping. The second example, from the Niobrara Formation and the lower Pierre Shale of the southeastern Powder River basin, is used to illustrate the complexities that can result from multiple sequences of progradation. The third example, the regressive part of the Lewis Shale of the Washakie and Red Desert basins, includes thick sandstone bodies. For each example, the areas assigned to the shelf, slope, and basin environments are determined from isopach maps of time-stratigraphic units within each section. This type of analysis is useful in solving problems of paleogeography and paleoecology. In the Upper Cretaceous of Wyoming, analysis indicates previously unrecognized complexities in the basin-filling process and the resulting sequence of units. The areal distribution of the three environments, the lithologic characteristics of the rocks, and the volume of sediment deposited in each environment are functions of the balance between rate of subsidence and sediment supply. The lower Pierre Shale and the Niobrara Formation of the Powder River basin are examples of the “wide-shelf” configuration, in which subsidence is relatively slow, progradation is rapid, and sand is largely confined to the shelf. The regressive Lewis Shale of the Washakie and Red Desert basins illustrates the complex relations between a “narrow shelf”-delta sequence (Lewis Shale) and a barrier island-lagoon sequence (Fox Hills Sandstone and Lance Formation). The submarine topography within a basin at a particular time in the sequence of deposition (the relief between the shelf edge and the basin, and the water depth in the basin environment) can be estimated from the present thickness of slope deposits. These estimates require correction for compaction and for water depth at the outer edge of the shelf. Such estimates indicate that at times the depth of water in areas of active sedimentation exceeded 2,000 ft. The Upper Cretaceous section of the Western Interior long has been considered a “textbook example” of shallow-water sedimentation. It has been studied by hundreds of geologists with varied interests and from different backgrounds, including the petroleum industry, the Geological Survey, and academic institutions. The section abounds with excellent time-stratigraphic correlations, and well control is more than adequate for detailed study in many areas. The fact that the relations described here could be overlooked under conditions such as these shows that they may have been missed in stratigraphic sections in other areas.

@article{doi1013065d25cbb316c111d78645000102c1865d,
    author = "Asquith, D. O.",
    title = "Depositional Topography and Major Marine Environments, Late Cretaceous, Wyoming",
    year = "1970",
    journal = "AAPG Bulletin",
    abstract = "Abstract Detailed correlation of electric-log resistivity patterns that result from variations in bentonite content of marine shale and siltstone reveals the presence of inclined time-stratigraphic units within the post-Turonian, marine Late Cretaceous section of Wyoming. Similar units have been recognized in rocks of the Permo-Pennsylvanian of Texas, the Devonian of Alberta, and the Mississippian of Illinois, and are attributed to submarine depositional topography. This interpretation, applied to the Late Cretaceous section of Wyoming, divides the epicontinental marine section into three major environments: shelf, slope, and basin. The inclined time-stratigraphic units were deposited on the slope, whereas thinner, more flat-lying units were deposited on the shelf and in the basin. Three examples demonstrate the wide areal distribution and the almost continuous presence of significant submarine topography in at least part of Wyoming during post-Turonian Late Cretaceous time. The first example, from the lower Cody Shale of the southeastern Big Horn basin, is used to introduce the concepts involved and methods of correlation and mapping. The second example, from the Niobrara Formation and the lower Pierre Shale of the southeastern Powder River basin, is used to illustrate the complexities that can result from multiple sequences of progradation. The third example, the regressive part of the Lewis Shale of the Washakie and Red Desert basins, includes thick sandstone bodies. For each example, the areas assigned to the shelf, slope, and basin environments are determined from isopach maps of time-stratigraphic units within each section. This type of analysis is useful in solving problems of paleogeography and paleoecology. In the Upper Cretaceous of Wyoming, analysis indicates previously unrecognized complexities in the basin-filling process and the resulting sequence of units. The areal distribution of the three environments, the lithologic characteristics of the rocks, and the volume of sediment deposited in each environment are functions of the balance between rate of subsidence and sediment supply. The lower Pierre Shale and the Niobrara Formation of the Powder River basin are examples of the “wide-shelf” configuration, in which subsidence is relatively slow, progradation is rapid, and sand is largely confined to the shelf. The regressive Lewis Shale of the Washakie and Red Desert basins illustrates the complex relations between a “narrow shelf”-delta sequence (Lewis Shale) and a barrier island-lagoon sequence (Fox Hills Sandstone and Lance Formation). The submarine topography within a basin at a particular time in the sequence of deposition (the relief between the shelf edge and the basin, and the water depth in the basin environment) can be estimated from the present thickness of slope deposits. These estimates require correction for compaction and for water depth at the outer edge of the shelf. Such estimates indicate that at times the depth of water in areas of active sedimentation exceeded 2,000 ft. The Upper Cretaceous section of the Western Interior long has been considered a “textbook example” of shallow-water sedimentation. It has been studied by hundreds of geologists with varied interests and from different backgrounds, including the petroleum industry, the Geological Survey, and academic institutions. The section abounds with excellent time-stratigraphic correlations, and well control is more than adequate for detailed study in many areas. The fact that the relations described here could be overlooked under conditions such as these shows that they may have been missed in stratigraphic sections in other areas.",
    url = "https://doi.org/10.1306/5d25cbb3-16c1-11d7-8645000102c1865d",
    doi = "10.1306/5d25cbb3-16c1-11d7-8645000102c1865d",
    openalex = "W2108407536",
    references = "doi101029jz069i020p04257, doi101130001676061951621tceoda20co2, doi101130001676061952631011cotcfo20co2, doi1013060bda5b8816bd11d78645000102c1865d, doi1013060bda5c9f16bd11d78645000102c1865d, doi1013060bda5f6f16bd11d78645000102c1865d, doi1013063d93436d16b111d78645000102c1865d, doi1013065d25b71316c111d78645000102c1865d, doi1013065d25c27f16c111d78645000102c1865d, olivers1965depositional"
}

Abstract Predominantly nonmarine early Tertiary sediments of the Wilcox Group in Texas include numerous local lignite deposits. Recent subsurface mapping has defined several interrelated depositional systems representing six sedimentary environments, in outcropping and subsurface Wilcox in Texas. Lignite occurs in three of the environments so defined; these are (1) fluvial, (2) deltaic, and (3) lagoonal. Plant microfossils and coal macerals from the Wilcox lignites comprise a relatively homogenous, recurring association, but substantial differences also exist between the lignites from the various environments. Petrographic differences include: (1) greater abundances of certain lithotypes, (2) predominance of certain macerals, (3) relative abundance of mineral matter. Palynologic differences can be summarized in terms of distribution of assemblages and species groups within the flora. Assemblages recognized are the (1) Corylus‐Sphagnum Assemblage, (2) Palm Assemblage, and (3) Marine Influence Assemblage. Species groups include (1) locally indigenous forms, (2) reworked forms, (3) temperate genera and (4) tropical genera. Quantitative distinctions within the flora are suggested by species diversity indices. Paleoecologic inferences derived from this study suggest agreement with environmental interpretations based on mapping. This study is seen as a basis for further biostratigraphic and paleoecologic investigations in the Gulf Coast Tertiary.

@article{doi1010800072139519719989707,
    author = "Nichols, Douglas J. and Traverse, Alfred",
    title = "Palynology, petrology, and depositional environments of some early tertiary lignites in Texas",
    year = "1971",
    journal = "Geoscience and Man",
    abstract = "Abstract Predominantly nonmarine early Tertiary sediments of the Wilcox Group in Texas include numerous local lignite deposits. Recent subsurface mapping has defined several interrelated depositional systems representing six sedimentary environments, in outcropping and subsurface Wilcox in Texas. Lignite occurs in three of the environments so defined; these are (1) fluvial, (2) deltaic, and (3) lagoonal. Plant microfossils and coal macerals from the Wilcox lignites comprise a relatively homogenous, recurring association, but substantial differences also exist between the lignites from the various environments. Petrographic differences include: (1) greater abundances of certain lithotypes, (2) predominance of certain macerals, (3) relative abundance of mineral matter. Palynologic differences can be summarized in terms of distribution of assemblages and species groups within the flora. Assemblages recognized are the (1) Corylus‐Sphagnum Assemblage, (2) Palm Assemblage, and (3) Marine Influence Assemblage. Species groups include (1) locally indigenous forms, (2) reworked forms, (3) temperate genera and (4) tropical genera. Quantitative distinctions within the flora are suggested by species diversity indices. Paleoecologic inferences derived from this study suggest agreement with environmental interpretations based on mapping. This study is seen as a basis for further biostratigraphic and paleoecologic investigations in the Gulf Coast Tertiary.",
    url = "https://doi.org/10.1080/00721395.1971.9989707",
    doi = "10.1080/00721395.1971.9989707",
    openalex = "W2065825799",
    references = "doi101130gsab541713, doi1013065ceae1c616bb11d78645000102c1865d"
}

@misc{tourtelot1971the,
    author = "Tourtelot, Harry Allison and Tailleur, Irvin L.",
    title = "The Shublik Formation and adjacent strata in northeastern Alaska description, minor elements, depositional environments and diagenesis",
    year = "1971",
    booktitle = "Open-File Report",
    url = "https://doi.org/10.3133/ofr71284",
    doi = "10.3133/ofr71284"
}

@article{harrywdodge1983depositional,
    author = "Harry W. Dodge, Jr., Thomas M. Cran",
    title = "Depositional Environments of Upper Cretaceous Fox Hills Formation, Niobrara and Weston Counties, East-Central Wyoming: ABSTRACT",
    year = "1983",
    journal = "AAPG Bulletin",
    url = "https://doi.org/10.1306/03b5b835-16d1-11d7-8645000102c1865d",
    doi = "10.1306/03b5b835-16d1-11d7-8645000102c1865d",
    volume = "67"
}

@article{darrensdueitt1985depositional,
    author = "Darren S. Dueitt, Franz Froelicher",
    title = "Depositional Environments of Wilcox Lignites in Choctaw and Winston Counties, Mississippi: ABSTRACT",
    year = "1985",
    journal = "AAPG Bulletin",
    url = "https://doi.org/10.1306/ad462cb3-16f7-11d7-8645000102c1865d",
    doi = "10.1306/ad462cb3-16f7-11d7-8645000102c1865d",
    volume = "69"
}

The Shublik Formation is a heterogeneous unit consisting of several distinct facies, including: 1) fossiliferous sandstone or siltstone: 2) glauconitic sandstone or siltstone: 3) siltstone, calcareous mudstone, or limestone with phosphate nodules; and 4) black, calcareous mudstone or black limestone, usually fossiliferous. This sequence of lithologies is interpreted as having been deposited along an onshore-offsh ore (north to south) gradient. Bioturbation of the sediments is variable, but generally decreases offshore. Organic carbon increases offshore and phosphate increases from the paleoshoreline and decreases again farthest offshore. The distribution of glauconite, phosphate, and organic-carbon-rich rock is consistent with the facies expected in an upwelling zone that has a well-developed oxygen minimum. Glauconite is consistent with dysoxic conditions and well-laminated, organiccarbon-rich rock in the offshore facies is consistent with anoxic conditions. High biologic productivity coupled with normal oceanic circulation may have caused the basin's low-oxygen conditions, as indicated by the presence of phosphate nodules and the extreme abundance of bivalves that have been interpreted to be pelagic. Phosphate indicates a high rate of supply of organic matter to the sediment-water interface, where it was mobilized from the organic matter within the anoxic zone and reprecipitated at the zone's edges. Pelagic bivalves (Monotis and Halobia) are present in such huge numbers as to suggest unusually abundant food supply; in addition, their distribution is consistent with mass kills, which are common among fish in upwelling zones. Although an open-ocean divergence was predicted previously for the North Slope region in the Triassic, the distribution of the facies of the Shublik Formation relative to the paleoshoreline and the rapidity of the facies change onshore to offshore are more consistent with a coastal upwelling zone.

@article{openalexw2140021650,
    author = "Parrish, Judith Totman",
    title = "Lithology, Geochemistry, and Depositional Environment of the Triassic Shublik Formation, Northern Alaska",
    year = "1987",
    abstract = "The Shublik Formation is a heterogeneous unit consisting of several distinct facies, including: 1) fossiliferous sandstone or siltstone: 2) glauconitic sandstone or siltstone: 3) siltstone, calcareous mudstone, or limestone with phosphate nodules; and 4) black, calcareous mudstone or black limestone, usually fossiliferous. This sequence of lithologies is interpreted as having been deposited along an onshore-offsh ore (north to south) gradient. Bioturbation of the sediments is variable, but generally decreases offshore. Organic carbon increases offshore and phosphate increases from the paleoshoreline and decreases again farthest offshore. The distribution of glauconite, phosphate, and organic-carbon-rich rock is consistent with the facies expected in an upwelling zone that has a well-developed oxygen minimum. Glauconite is consistent with dysoxic conditions and well-laminated, organiccarbon-rich rock in the offshore facies is consistent with anoxic conditions. High biologic productivity coupled with normal oceanic circulation may have caused the basin's low-oxygen conditions, as indicated by the presence of phosphate nodules and the extreme abundance of bivalves that have been interpreted to be pelagic. Phosphate indicates a high rate of supply of organic matter to the sediment-water interface, where it was mobilized from the organic matter within the anoxic zone and reprecipitated at the zone's edges. Pelagic bivalves (Monotis and Halobia) are present in such huge numbers as to suggest unusually abundant food supply; in addition, their distribution is consistent with mass kills, which are common among fish in upwelling zones. Although an open-ocean divergence was predicted previously for the North Slope region in the Triassic, the distribution of the facies of the Shublik Formation relative to the paleoshoreline and the rapidity of the facies change onshore to offshore are more consistent with a coastal upwelling zone.",
    openalex = "W2140021650"
}

@article{bergan1988shoreline,
    author = "Bergan, Gail R.",
    title = "Shoreline Depositional Environments of Glen Rose Formation (Lower Cretaceous) in Type Area, Somervell and Hood Counties, Texas: ABSTRACT",
    year = "1988",
    journal = "AAPG Bulletin",
    url = "https://doi.org/10.1306/703c97e4-1707-11d7-8645000102c1865d",
    doi = "10.1306/703c97e4-1707-11d7-8645000102c1865d",
    volume = "72"
}

@misc{leipzig1990the1,
    author = "Leipzig, M. R",
    title = "The stratigraphy, electrofacies and depositional environments of the Reklaw Formation of Goliad and adjacent counties, south Texas",
    year = "1990",
    howpublished = "American Association of Petroleum Geologists, v. 215, no. 1, p. 76- 84",
    note = "talkorigins\_source = {true}; raw\_reference = {Leipzig, M. R., 1990, The stratigraphy, electrofacies and depositional environments of the Reklaw Formation of Goliad and adjacent counties, south Texas: American Association of Petroleum Geologists, v. 215, no. 1, p. 76- 84.}"
}

@misc{crossref1995geology,
    title = "Geology and hydrogeology of Naval Air Station Chase Field and Naval Auxiliary Landing Field Goliad, Bee and Goliad counties, Texas",
    year = "1995",
    url = "https://doi.org/10.3133/wri954038",
    doi = "10.3133/wri954038",
    openalex = "W2145055040",
    references = "doi1010160309170881900294, doi101029jz065i011p03713, doi101029jz068i016p04795, doi101029tr016i002p00519, doi101029tr027i004p00526, doi101029tr036i001p00095, doi101086624930, doi1023071788077, openalexw2103810229, openalexw2151171819"
}

ABSTRACT The Upper Triassic Shublik Formation within the Prudhoe Bay field unit, North Slope, Alaska, is a potentially economic hydrocarbon reservoir comprised of mixed lithology and mineralogy. Its composition includes limestone, phosphate, shale, siltstone, and sandstone, as well as accessory amounts of siderite, glauconite, pyrite, kaolinite, and dolomite. Within the Prudhoe Bay field unit, the Shublik has been subdivided into four zones, lettered from base to top, D through A, which become thinner and show evidence of deposition under higher energy conditions toward the northeast. The formation is truncated to the east by the regional Lower Cretaceous unconformity. Zones within the Shublik comprise a basal transgressive systems tract (conglomerate lag at the Shublik Formation/Ivishak Formation contact through basal zone C shales) and two highstand shallowing-upward parasequences (zones C through B, and zone A, respectively). The parasequences are bounded by shales interpreted to represent deposition during periods of marine flooding. The contact between the Shublik and the overlying Sag River Formation juxtaposes comparatively deeper marine Shublik with shallower water glauconitic sandstones of the Sag River Formation. The contact is unconformable and is interpreted to represent a regional sequence boundary. Lithofacies of the Shublik are interpreted to have been coeval depositional facies of an upwelling system. Relative sea level changes during Shublik deposition are interpreted to have caused the observed vertical and lateral variability in lithofacies via systematic changes between anaerobic, dysaerobic, and aerobic upwelling conditions. Dissolution of carbonate allochems resulted in the creation of moldic porosity that positively affected reservoir quality (i.e., permeability) in the carbonate packstone/grainstone facies. Areas of highest porosity are in the northern and northeastern parts of the field, which correspond to a combination of facies-controlled reservoir quality improvement toward the northeast and carbonate dissolution along the Lower Cretaceous unconformity and the North Prudhoe Bay fault zone. Oil in place for the Shublik within the Prudhoe Bay unit is estimated to be between 250 and 500 million bbl. Although permeabilities are generally low throughout the field area, the Shublik Formation has the potential to add significant reserves to the Prudhoe Bay field unit.

@article{doi1013067834d4ae172111d78645000102c1865d,
    author = "Kupecz, Julie A.",
    title = "Depositional Setting, Sequence Stratigraphy, Diagenesis, and Reservoir Potential of a Mixed-Lithology, Upwelling Deposit: Upper Triassic Shublik Formation, Prudhoe Bay, Alaska",
    year = "1995",
    journal = "AAPG Bulletin",
    abstract = "ABSTRACT The Upper Triassic Shublik Formation within the Prudhoe Bay field unit, North Slope, Alaska, is a potentially economic hydrocarbon reservoir comprised of mixed lithology and mineralogy. Its composition includes limestone, phosphate, shale, siltstone, and sandstone, as well as accessory amounts of siderite, glauconite, pyrite, kaolinite, and dolomite. Within the Prudhoe Bay field unit, the Shublik has been subdivided into four zones, lettered from base to top, D through A, which become thinner and show evidence of deposition under higher energy conditions toward the northeast. The formation is truncated to the east by the regional Lower Cretaceous unconformity. Zones within the Shublik comprise a basal transgressive systems tract (conglomerate lag at the Shublik Formation/Ivishak Formation contact through basal zone C shales) and two highstand shallowing-upward parasequences (zones C through B, and zone A, respectively). The parasequences are bounded by shales interpreted to represent deposition during periods of marine flooding. The contact between the Shublik and the overlying Sag River Formation juxtaposes comparatively deeper marine Shublik with shallower water glauconitic sandstones of the Sag River Formation. The contact is unconformable and is interpreted to represent a regional sequence boundary. Lithofacies of the Shublik are interpreted to have been coeval depositional facies of an upwelling system. Relative sea level changes during Shublik deposition are interpreted to have caused the observed vertical and lateral variability in lithofacies via systematic changes between anaerobic, dysaerobic, and aerobic upwelling conditions. Dissolution of carbonate allochems resulted in the creation of moldic porosity that positively affected reservoir quality (i.e., permeability) in the carbonate packstone/grainstone facies. Areas of highest porosity are in the northern and northeastern parts of the field, which correspond to a combination of facies-controlled reservoir quality improvement toward the northeast and carbonate dissolution along the Lower Cretaceous unconformity and the North Prudhoe Bay fault zone. Oil in place for the Shublik within the Prudhoe Bay unit is estimated to be between 250 and 500 million bbl. Although permeabilities are generally low throughout the field area, the Shublik Formation has the potential to add significant reserves to the Prudhoe Bay field unit.",
    url = "https://doi.org/10.1306/7834d4ae-1721-11d7-8645000102c1865d",
    doi = "10.1306/7834d4ae-1721-11d7-8645000102c1865d",
    openalex = "W2006860727",
    references = "doi104095100966"
}

@article{jamescslone12000abstract,
    author = "James C Slone1, Jim Mazzullo1",
    title = "Abstract: Facies and depositional environments of the Permian Queen Formation, Howard Glasscock Field, Glasscock and Sterling Counties, Texas",
    year = "2000",
    journal = "AAPG Bulletin",
    url = "https://doi.org/10.1306/a9672eec-1738-11d7-8645000102c1865d",
    doi = "10.1306/a9672eec-1738-11d7-8645000102c1865d",
    volume = "84 (2000)"
}

Abstract The Shublik Formation (Triassic, North Slope, Alaska) is an organic-, phosphate-, and glauconite-rich unit with abundant fossils of marine vertebrates and mollusks. Five lithofacies, generalized around significant chemical constituents or lack thereof, are identified in the Shublik Formation:nonglauconitic sandstone - thin- to medium-bedded, fine, quartzose, calcareous to noncalcareous sandstone or silty to muddy sandstone, fossiliferous in places;glauconitic - thin- to medium-bedded, fine, quartzose sandstone, muddy sandstone, or siltstone containing 10% to > 50% glauconite grainsphosphatic - thin- to medium-bedded siltstone or sandstone or laminated, black silty limestone or limestone containing phosphate nodules; andorganic-rich - laminated, black limestone, marl, and mudstonenonphosphatic, nonorganic-rich limestone - bioclastic wackestone, or argillaceous grainstone and packstone or graded grainstone and packstone. Ichnofabrics provide evidence of fluctuating oxygen levels within the facies, especially the nonglauconitic sandstone and glauconitic facies. The organic-rich facies and, to a lesser extent, the phosphatic facies contain abundant, pristine, disarticulated shells of the clam Halobia. The lithofacies, ichnofabrics, and taphonomy are interpreted to be related to onshore-offshore gradients in biologic productivity and redox conditions. The Shublik Formation is interpreted as an upwelling-zone deposit formed on a shallow shelf. The Shublik Formation in the Prudhoe Bay region is interpreted to comprise three sequences; these have been extended to outcrop but not to cores in the National Petroleum Reserve. Facies stacking patterns indicate that siliclastic facies are most common during lowstand and transgression, organic-rich facies are characteristic of transgression, and carbonate-rich facies are more prevalent during highstand. Phosphatic facies occur along transgressive and maximum flooding surfaces and are thus integral to subdividing sequences into systems tracts.

@incollection{doi102110cor01010089,
    author = "Parrish, Judith Totman and Whalen, Michael T. and Hulm, Erik",
    title = "Shublik Formation Lithofacies, Environments, and Sequence Stratigraphy, Arctic Alaska, U.S.A.",
    year = "2001",
    booktitle = "SEPM (Society for Sedimentary Geology) eBooks",
    abstract = "Abstract The Shublik Formation (Triassic, North Slope, Alaska) is an organic-, phosphate-, and glauconite-rich unit with abundant fossils of marine vertebrates and mollusks. Five lithofacies, generalized around significant chemical constituents or lack thereof, are identified in the Shublik Formation:nonglauconitic sandstone - thin- to medium-bedded, fine, quartzose, calcareous to noncalcareous sandstone or silty to muddy sandstone, fossiliferous in places;glauconitic - thin- to medium-bedded, fine, quartzose sandstone, muddy sandstone, or siltstone containing 10\% to \> 50\% glauconite grainsphosphatic - thin- to medium-bedded siltstone or sandstone or laminated, black silty limestone or limestone containing phosphate nodules; andorganic-rich - laminated, black limestone, marl, and mudstonenonphosphatic, nonorganic-rich limestone - bioclastic wackestone, or argillaceous grainstone and packstone or graded grainstone and packstone. Ichnofabrics provide evidence of fluctuating oxygen levels within the facies, especially the nonglauconitic sandstone and glauconitic facies. The organic-rich facies and, to a lesser extent, the phosphatic facies contain abundant, pristine, disarticulated shells of the clam Halobia. The lithofacies, ichnofabrics, and taphonomy are interpreted to be related to onshore-offshore gradients in biologic productivity and redox conditions. The Shublik Formation is interpreted as an upwelling-zone deposit formed on a shallow shelf. The Shublik Formation in the Prudhoe Bay region is interpreted to comprise three sequences; these have been extended to outcrop but not to cores in the National Petroleum Reserve. Facies stacking patterns indicate that siliclastic facies are most common during lowstand and transgression, organic-rich facies are characteristic of transgression, and carbonate-rich facies are more prevalent during highstand. Phosphatic facies occur along transgressive and maximum flooding surfaces and are thus integral to subdividing sequences into systems tracts.",
    url = "https://doi.org/10.2110/cor.01.01.0089",
    doi = "10.2110/cor.01.01.0089",
    openalex = "W2209195447",
    references = "doi1010160016703796000415, doi10113000917613198614535scaia20co2, doi101130dnaggnag149, doi10130603b5a30e16d111d78645000102c1865d, doi101306bdff8aa6171811d78645000102c1865d, doi101306m26490c14, doi102110pec88010039, doi102110pec88010183, doi102110pec9412, doi102110pec94120045, doi104095100966, tourtelot1971the"
}

@incollection{crossref2003depositional,
    title = "Depositional Environments of Clay Seal Formation",
    year = "2003",
    booktitle = "Clay Seals of Oil and Gas Deposits",
    url = "https://doi.org/10.1201/noe9058095831.ch4",
    doi = "10.1201/noe9058095831.ch4",
    pages = "120-135"
}

Peat depositional environments, the sites where and conditions under which peat accumulates, significantly influence a resultant coal's physical properties, chemical composition, and coal utilization behavior. Recognition of peat depositional environments for coal is a challenging endeavor because coal's observed compositional properties not only result from a variety of geological processes operating during peat accumulation, but also reflect the influence of adjoining or external depositional sedimentary environments and alteration during later diagenesis and/or epigenesis. The maceral or microlithotype composition of any one layer of peat can be the product of years or decades of plant growth, death, decay, and post-burial infiltration by roots in addition to the symbiotic, mutualistic, parasitic, and saprophytic relationships with non-plant biota, such as arthropods, fungi, and bacteria. The overprint of increasing thermal maturation and fluid migration through time on the resulting coal can make these relationships difficult to recognize. Therefore, published models based on maceral composition alone must be used with great caution. Lipid compositions, even from lipid-poor low-rank coals, can provide important information about depositional environments and paleoclimate, especially if combined with the results of organic petrography and paleontological studies. Just as sulfur derived from seawater provides environmental clues, the ratios of two particularly relevant trace elements rather than a single trace element can be used to interpret peat depositional environments. Epigenetic minerals, as well as their corresponding chemical compositions should not be used for such a purpose; similarly, resistant terrigenous minerals deposited during peat accumulation in many cases should be used with considerable caution. The interactions of the biota present in the peat-forming ecosystem, often determined using palynological and geochemical proxies, and their interpretation in the context of geography and paleoclimate are important means for deciphering peat depositional environments. Overall, a combination of evidence from geochemistry, mineralogy, palynology, and petrology of coal and from stratigraphy, sedimentology, and sedimentary facies of related rocks is necessary for accurate and comprehensive determination of depositional environments. The need for interdisciplinary studies is underscored by peat compositional properties, which have been greatly affected by various processes during the syngenetic, diagenetic or epigenetic stages of coal formation.

@article{doi101016jcoal2019103383,
    author = "Dai, Shifeng and Bechtel, Achim and Eble, Cortland F. and Flores, Romeo M. and French, David and Graham, Ian T. and Hood, Madison M. and Hower, James C. and Korasidis, Vera A. and Moore, Tim A. and Püttmann, Wilhelm and Wei, Qiang and Zhao, Lei and O’Keefe, Jennifer M.K.",
    title = "Recognition of peat depositional environments in coal: A review",
    year = "2020",
    journal = "International Journal of Coal Geology",
    abstract = "Peat depositional environments, the sites where and conditions under which peat accumulates, significantly influence a resultant coal's physical properties, chemical composition, and coal utilization behavior. Recognition of peat depositional environments for coal is a challenging endeavor because coal's observed compositional properties not only result from a variety of geological processes operating during peat accumulation, but also reflect the influence of adjoining or external depositional sedimentary environments and alteration during later diagenesis and/or epigenesis. The maceral or microlithotype composition of any one layer of peat can be the product of years or decades of plant growth, death, decay, and post-burial infiltration by roots in addition to the symbiotic, mutualistic, parasitic, and saprophytic relationships with non-plant biota, such as arthropods, fungi, and bacteria. The overprint of increasing thermal maturation and fluid migration through time on the resulting coal can make these relationships difficult to recognize. Therefore, published models based on maceral composition alone must be used with great caution. Lipid compositions, even from lipid-poor low-rank coals, can provide important information about depositional environments and paleoclimate, especially if combined with the results of organic petrography and paleontological studies. Just as sulfur derived from seawater provides environmental clues, the ratios of two particularly relevant trace elements rather than a single trace element can be used to interpret peat depositional environments. Epigenetic minerals, as well as their corresponding chemical compositions should not be used for such a purpose; similarly, resistant terrigenous minerals deposited during peat accumulation in many cases should be used with considerable caution. The interactions of the biota present in the peat-forming ecosystem, often determined using palynological and geochemical proxies, and their interpretation in the context of geography and paleoclimate are important means for deciphering peat depositional environments. Overall, a combination of evidence from geochemistry, mineralogy, palynology, and petrology of coal and from stratigraphy, sedimentology, and sedimentary facies of related rocks is necessary for accurate and comprehensive determination of depositional environments. The need for interdisciplinary studies is underscored by peat compositional properties, which have been greatly affected by various processes during the syngenetic, diagenetic or epigenetic stages of coal formation.",
    url = "https://doi.org/10.1016/j.coal.2019.103383",
    doi = "10.1016/j.coal.2019.103383",
    openalex = "W2998976463",
    references = "doi101016000925419490085x, doi1010160012825287900419, doi1010160031920186900932, doi1010160166516284900193, doi101016jchemgeo200312009, doi101016jcoal200303001, doi101016jcoal201202004, doi101016jcoal201205009, doi101016jcoal2019103304, doi101016jearscirev200810003, doi101016jfbr200709001, doi101016s0009254198001429, doi101016s0166516202001179, doi101017cbo9780511524868, doi101038272216a0, doi10108003115517708527763, doi10113000917613198614535scaia20co2, doi101344105000001619, doi1023071485834, doi1023072844758, doi105860choice301532, doi105860choice302690, doi105860choice444462, openalexw1624806571"
}

In the Yangtze Block, the Early Cambrian Niutitang Formation is mainly composed of mudstone, shale, and carbonates which are important for investigating the depositional environment and evolution of the Early Cambrian rocks. The Niutitang Formation in the study area has a greater geologic interest due to its polymetallic beds, depositional age, variation in environmental conditions, Cambrian explosion, organic matter (OM) enrichment, algal boom, etc. This research represents the sedimentary geochemistry of the Early Cambrian Niutitang Formation to reconstruct the palaeo‐depositional environment and to evaluate the OM enrichment mechanism by means of total organic carbon (TOC), biomarkers, carbon isotopes, mineralogy, scanning electron microscope, etc. Based on the variation in TOC content, the Niutitang Formation is divided into three parts (upper, middle, and lower). The majority of the samples from the middle part of the Niutitang Formation exhibit an excellent source of hydrocarbon (TOC > 4.0 wt%) relative to the upper and the lower part. The lighter carbon isotopic composition (<−30.7%) in these sediments reveals the presence of the I‐amorphous kerogen group. Moreover, these lighter δ 13 C org values suggest the presence of type‐I oil‐prone kerogen. Saturated hydrocarbon in these rocks showed the dominance of short‐chain n ‐alkanes maximizing at C 18. The predominance of these n ‐alkanes represents that the OM is chiefly derived from algal/bacterial input. Similarly, the dissymmetric V shape of C 27 ‐C 28 ‐C 29 steranes with a predominance of C 27 and the higher values of in all three parts reflects that the OM in these rocks is chiefly originated from the lower aquatic marine organisms. Based on the Pr/Ph ratio, it is predicted that the middle part of the Niutitang Formation was deposited in extreme anoxic conditions (Pr/Ph < 0.5), whereas the upper and lower parts were deposited in relatively less anoxic conditions. Some biomarkers have more stable stereochemistry, which cannot be affected by diagenetic processes. These stable configurations are utilized to measure the maturity of OM, that is, Ts/(Ts + Tm), C 29 ββ/(ββ + αα), C 29 αα20S/(20S + 20R) steranes, and homohopane C 31 22S/(22S + 22R). These geochemical indices reveal that the Early Cambrian Niutitang Formation in the studied area is mature to the post‐mature in the gas generation phase. Moreover, the hydrothermal fluids rich in metallic elements (e.g., Mo, Zn, V, and U) from the deeper part of the Earth owing to elongational forces among Yangtze and Cathaysian plates over Early Cambrian time entered the oceanic basin via remnant features (fissure and cracks) and through upwelling phenomena interacted with shelf sediments. At the ocean's surface, these nutrient‐rich fluids enhanced the breeding and evolution of marine life (bio‐productivity), which created hypoxic water conditions suitable for the preservation of OM in these rocks.

@article{doi101002gj4304,
    author = "Awan, Rizwan Sarwar and Liu, Chenglin and Khan, Ashar and Zang, Qibiao and Wu, Yuping and Feng, Dehao",
    title = "Sedimentary geochemistry of the Early Cambrian Niutitang Formation to reconstruct the palaeo‐depositional environments and to evaluate the organic matter enrichment mechanism from the Yangtze Block, South China",
    year = "2021",
    journal = "Geological Journal",
    abstract = "In the Yangtze Block, the Early Cambrian Niutitang Formation is mainly composed of mudstone, shale, and carbonates which are important for investigating the depositional environment and evolution of the Early Cambrian rocks. The Niutitang Formation in the study area has a greater geologic interest due to its polymetallic beds, depositional age, variation in environmental conditions, Cambrian explosion, organic matter (OM) enrichment, algal boom, etc. This research represents the sedimentary geochemistry of the Early Cambrian Niutitang Formation to reconstruct the palaeo‐depositional environment and to evaluate the OM enrichment mechanism by means of total organic carbon (TOC), biomarkers, carbon isotopes, mineralogy, scanning electron microscope, etc. Based on the variation in TOC content, the Niutitang Formation is divided into three parts (upper, middle, and lower). The majority of the samples from the middle part of the Niutitang Formation exhibit an excellent source of hydrocarbon (TOC > 4.0 wt\%) relative to the upper and the lower part. The lighter carbon isotopic composition (<−30.7\%) in these sediments reveals the presence of the I‐amorphous kerogen group. Moreover, these lighter δ 13 C org values suggest the presence of type‐I oil‐prone kerogen. Saturated hydrocarbon in these rocks showed the dominance of short‐chain n ‐alkanes maximizing at C 18. The predominance of these n ‐alkanes represents that the OM is chiefly derived from algal/bacterial input. Similarly, the dissymmetric V shape of C 27 ‐C 28 ‐C 29 steranes with a predominance of C 27 and the higher values of in all three parts reflects that the OM in these rocks is chiefly originated from the lower aquatic marine organisms. Based on the Pr/Ph ratio, it is predicted that the middle part of the Niutitang Formation was deposited in extreme anoxic conditions (Pr/Ph < 0.5), whereas the upper and lower parts were deposited in relatively less anoxic conditions. Some biomarkers have more stable stereochemistry, which cannot be affected by diagenetic processes. These stable configurations are utilized to measure the maturity of OM, that is, Ts/(Ts + Tm), C 29 ββ/(ββ + αα), C 29 αα20S/(20S + 20R) steranes, and homohopane C 31 22S/(22S + 22R). These geochemical indices reveal that the Early Cambrian Niutitang Formation in the studied area is mature to the post‐mature in the gas generation phase. Moreover, the hydrothermal fluids rich in metallic elements (e.g., Mo, Zn, V, and U) from the deeper part of the Earth owing to elongational forces among Yangtze and Cathaysian plates over Early Cambrian time entered the oceanic basin via remnant features (fissure and cracks) and through upwelling phenomena interacted with shelf sediments. At the ocean's surface, these nutrient‐rich fluids enhanced the breeding and evolution of marine life (bio‐productivity), which created hypoxic water conditions suitable for the preservation of OM in these rocks.",
    url = "https://doi.org/10.1002/gj.4304",
    doi = "10.1002/gj.4304",
    openalex = "W3211106031",
    references = "doi102110cor01010089"
}

@article{lopatina2025the,
    author = "Lopatina, Ekaterina",
    title = "The differential diagnosis of tidal flat facies and adjacent depositional environments",
    year = "2025",
    journal = "Oil and gas geology = Geologiya nefti i gaza",
    url = "https://doi.org/10.47148/0016-7894-2024-6-31-43",
    doi = "10.47148/0016-7894-2024-6-31-43",
    number = "6",
    pages = "31-43"
}