Bearpaw shale

The sections of the Bearpaw shale herewith presented were prepared from a study of cuttings from many shallow test-holes and three deep wells, located within an area extending from T. 11 to T. 21 and from R. 18 to R. 23, W. of 4th Mer., in southern Alberta. In this area, the base of the Bearpaw shale is limited below by the coal measures at the top of the Pale beds, and at the top by the massive Fox Hills sandstone. The formation is 740 feet thick in the southern part of the area, but this thickness decreases northeastward 230 feet in 65 miles. The Bearpaw shale consists of three lithologic units. The lower shale member contains bentonite beds, but no sand. The middle sandstone member is generally a fine-grained massive sandstone useful for correlation. The upper sandy member contains sandy shale and erratic sandstone lenses which ordinarily can not be correlated between adjacent wells.

@article{clark1931sections,
    author = "Clark, Clare M.",
    title = "Sections of Bearpaw Shale from Keho Lake to Bassano, Southern Alberta",
    year = "1931",
    journal = "AAPG Bulletin",
    abstract = "The sections of the Bearpaw shale herewith presented were prepared from a study of cuttings from many shallow test-holes and three deep wells, located within an area extending from T. 11 to T. 21 and from R. 18 to R. 23, W. of 4th Mer., in southern Alberta. In this area, the base of the Bearpaw shale is limited below by the coal measures at the top of the Pale beds, and at the top by the massive Fox Hills sandstone. The formation is 740 feet thick in the southern part of the area, but this thickness decreases northeastward 230 feet in 65 miles. The Bearpaw shale consists of three lithologic units. The lower shale member contains bentonite beds, but no sand. The middle sandstone member is generally a fine-grained massive sandstone useful for correlation. The upper sandy member contains sandy shale and erratic sandstone lenses which ordinarily can not be correlated between adjacent wells.",
    url = "https://doi.org/10.1306/3d932a16-16b1-11d7-8645000102c1865d",
    doi = "10.1306/3d932a16-16b1-11d7-8645000102c1865d",
    number = "10",
    pages = "1243-1249",
    volume = "15"
}

The Bearpaw shale of the Lethbridge area is 726 feet thick. It contains at least twenty-two bentonite beds, three distinct sandstone phases, which have been named for local usage, a glauconite sand, and two zones with exceptional profusion of fossils. The overlying Fox Hills sandstone has a thickness of 142 feet, and consists primarily of one unbroken sequence of coarse, massive, greenish sandstone which weathers buff, with an Ostrea coquina near the top. The Lethbridge coal measures of the upper Belly River series contain several coal seams, two of which are commercial. The top is marked by a thin, brown-weathering sandstone and locally an Ostrea coquina is found above the top coal bed. Descriptions of these formations, with stratigraphic columns and a brief historical sketch, are submitted.

@article{link1931bearpaw,
    author = "Link, Theodore A. and Childerhose, A. J.",
    title = "Bearpaw Shale and Contiguous Formations in Lethbridge Area, Alberta",
    year = "1931",
    journal = "AAPG Bulletin",
    abstract = "The Bearpaw shale of the Lethbridge area is 726 feet thick. It contains at least twenty-two bentonite beds, three distinct sandstone phases, which have been named for local usage, a glauconite sand, and two zones with exceptional profusion of fossils. The overlying Fox Hills sandstone has a thickness of 142 feet, and consists primarily of one unbroken sequence of coarse, massive, greenish sandstone which weathers buff, with an Ostrea coquina near the top. The Lethbridge coal measures of the upper Belly River series contain several coal seams, two of which are commercial. The top is marked by a thin, brown-weathering sandstone and locally an Ostrea coquina is found above the top coal bed. Descriptions of these formations, with stratigraphic columns and a brief historical sketch, are submitted.",
    url = "https://doi.org/10.1306/3d932a14-16b1-11d7-8645000102c1865d",
    doi = "10.1306/3d932a14-16b1-11d7-8645000102c1865d",
    number = "10",
    pages = "1227-1242",
    volume = "15"
}

ABSTRACT The Upper Cretaceous deposits of the Gulf region are mainly of marine origin. Taking the east-central Texas section as a standard, the deposits present different sequences of units from place to place in both directions away from this section, both to the southwest and to the northeast. The sequence in east-central Texas resembles that in the Great Plains of the western interior. No other sequences in the two regions are similar to each other. The Upper Cretaceous of the western interior may be roughly divided into belts representing three types of sequence: (1) the Great Plains sequence—mainly fine sediments, and of marine origin; (2) the Rocky Mountain sequence—continental and marine sediments, much sandstone, considerable coal, increasing in coarseness westward; (3) a western marginal belt dominantly nonmarine, coarse sandstones, conglomerates, and coals; sequence usually incomplete. Fossils are abundant in both regions. Although many species are present in each region that are not found in the other, enough of them are common or closely analogous to permit a fairly close correlation of the deposits. Dependence for correlation is placed chiefly on the mollusks. Although there is at present no physical connection between the Upper Cretaceous deposits of the Gulf region and those of the western interior, the presence of common and closely analogous species throughout the series in the two areas indicates that there was such a connection. Presumably the connecting deposits that once existed in some part of the area now separating the two regions have been removed by erosion.

@article{doi1013063d93302016b111d78645000102c1865d,
    author = "Stephenson, Lloyd William and Reeside, John B.",
    title = "Comparison of Upper Cretaceous Deposits of Gulf Region and Western Interior Region",
    year = "1938",
    journal = "AAPG Bulletin",
    abstract = "ABSTRACT The Upper Cretaceous deposits of the Gulf region are mainly of marine origin. Taking the east-central Texas section as a standard, the deposits present different sequences of units from place to place in both directions away from this section, both to the southwest and to the northeast. The sequence in east-central Texas resembles that in the Great Plains of the western interior. No other sequences in the two regions are similar to each other. The Upper Cretaceous of the western interior may be roughly divided into belts representing three types of sequence: (1) the Great Plains sequence—mainly fine sediments, and of marine origin; (2) the Rocky Mountain sequence—continental and marine sediments, much sandstone, considerable coal, increasing in coarseness westward; (3) a western marginal belt dominantly nonmarine, coarse sandstones, conglomerates, and coals; sequence usually incomplete. Fossils are abundant in both regions. Although many species are present in each region that are not found in the other, enough of them are common or closely analogous to permit a fairly close correlation of the deposits. Dependence for correlation is placed chiefly on the mollusks. Although there is at present no physical connection between the Upper Cretaceous deposits of the Gulf region and those of the western interior, the presence of common and closely analogous species throughout the series in the two areas indicates that there was such a connection. Presumably the connecting deposits that once existed in some part of the area now separating the two regions have been removed by erosion.",
    url = "https://doi.org/10.1306/3d933020-16b1-11d7-8645000102c1865d",
    doi = "10.1306/3d933020-16b1-11d7-8645000102c1865d",
    openalex = "W2110317016"
}

Baculites mariasensis, B. sweetgrassensis and B. gregaryensis are described as new. The first two are of Niobrara age, and the last is from rocks of Judith River age. The baculite zones of the northern Great Plains are reviewed. M ANY collections of fossils from the Upper Cretaceous rocks of the western interior United States contain several undescribed species of baculites that are of value in correlation. Two new species, Baculites mariasensis and B. sweetgrassensis, occur in shale and sandstone equivalents of the Fort Hays limestone member of the Niobrara formation. B. gregoryensis, n. sp., occurs in marine rocks equivalent to the Judith River formation of central Montana. The recognition of these species makes it possible to construct a more complete Upper Cretaceous time scale for the Western Interior based on Baculites. The zones constitute the following sequence in the northern Great Plains. [B. grandis B. compressus Montana age B. gregoryensis B. asperiformis B. aquilaensis B. thomi B. codyensis Colorado age B. mariasensis B. cf. besairiei (B. gracilis Baculites gracilis Shumard characterizes the Greenhorn limestone of the Black Hills 1 Published by permission of the Director, U. S. Geological Survey. and the equivalent calcareous beds in the middle of the Colorado shale of northcentral Montana. Baculites cf. besairiei Collignon occurs in the Carlile shale of the lack Hills and in the equivalent part of the Colorado shale of Montana. B. mariasensis, n. sp., is present in the upper part of the Colorado shale of Montana and in the upper part of the Frontier formation of westc ntral Wyoming. B. codyensis Reeside, of upper Niobrara age, is abundant in the Cody shale of Wyoming and in the upper part of the Colorado shale of Montana (above the zone of B. mariasensis). B. thomi Reeside occurs in the uppermost part of the Colorado shale of north-central Montana and in the Telegraph Creek formation of north-central and south-central Montana. B. aquilaensis Reeside characterizes the Eagle sandstone of Montana, the Gammon ferruginous member of the Pierre shale of the Black Hills, and parts of the Steele and Cody shales of Wyoming. B. asperiformis Meek is the most common form in the Claggett shale of Montana and in the Mitten black shale member of the Pierre shale of the Black Hills. B. gregoryensis, n. sp., occurs in the calcareous Gregory member of the Pierre shale in the Missouri Valley of South Dakota, and in a 200-foot sandy shale member of the Pierre EXPLANATION OF PLATE 118 All figures natural size. FIGS. 1-5-Baculites gregoryensis Cobban, n. sp. 1, Lateral view of holotype; 2-5, lateral views of four paratypes. Gregory member of Pierre shale, 2 miles west of Oacoma, Lyman County, South Dakota. (p. 820) 6-9-Baculites sweetgrassensis Cobban, n. sp. 6, 7, Lateral and ventral views of paratype; 8, 9, lateral and ventral views of holotype. Colorado shale, 5.5 miles south of Shelby, Toole County, Montana. (p. 820) 10-12-Baculites mariasensis Cobban, n. sp. 10, 11, Lateral views of paratypes; 12, lateral view of holotype. Colorado shale, 5.5 miles south of Shelby, Toole County, Montana. (p. 818)

@article{openalexw2528031705,
    author = "Cobban, W. A.",
    title = "New species of Baculites from the Upper Cretaceous of Montana and South Dakota",
    year = "1951",
    journal = "Journal of Paleontology",
    abstract = "Baculites mariasensis, B. sweetgrassensis and B. gregaryensis are described as new. The first two are of Niobrara age, and the last is from rocks of Judith River age. The baculite zones of the northern Great Plains are reviewed. M ANY collections of fossils from the Upper Cretaceous rocks of the western interior United States contain several undescribed species of baculites that are of value in correlation. Two new species, Baculites mariasensis and B. sweetgrassensis, occur in shale and sandstone equivalents of the Fort Hays limestone member of the Niobrara formation. B. gregoryensis, n. sp., occurs in marine rocks equivalent to the Judith River formation of central Montana. The recognition of these species makes it possible to construct a more complete Upper Cretaceous time scale for the Western Interior based on Baculites. The zones constitute the following sequence in the northern Great Plains. [B. grandis B. compressus Montana age B. gregoryensis B. asperiformis B. aquilaensis B. thomi B. codyensis Colorado age B. mariasensis B. cf. besairiei (B. gracilis Baculites gracilis Shumard characterizes the Greenhorn limestone of the Black Hills 1 Published by permission of the Director, U. S. Geological Survey. and the equivalent calcareous beds in the middle of the Colorado shale of northcentral Montana. Baculites cf. besairiei Collignon occurs in the Carlile shale of the lack Hills and in the equivalent part of the Colorado shale of Montana. B. mariasensis, n. sp., is present in the upper part of the Colorado shale of Montana and in the upper part of the Frontier formation of westc ntral Wyoming. B. codyensis Reeside, of upper Niobrara age, is abundant in the Cody shale of Wyoming and in the upper part of the Colorado shale of Montana (above the zone of B. mariasensis). B. thomi Reeside occurs in the uppermost part of the Colorado shale of north-central Montana and in the Telegraph Creek formation of north-central and south-central Montana. B. aquilaensis Reeside characterizes the Eagle sandstone of Montana, the Gammon ferruginous member of the Pierre shale of the Black Hills, and parts of the Steele and Cody shales of Wyoming. B. asperiformis Meek is the most common form in the Claggett shale of Montana and in the Mitten black shale member of the Pierre shale of the Black Hills. B. gregoryensis, n. sp., occurs in the calcareous Gregory member of the Pierre shale in the Missouri Valley of South Dakota, and in a 200-foot sandy shale member of the Pierre EXPLANATION OF PLATE 118 All figures natural size. FIGS. 1-5-Baculites gregoryensis Cobban, n. sp. 1, Lateral view of holotype; 2-5, lateral views of four paratypes. Gregory member of Pierre shale, 2 miles west of Oacoma, Lyman County, South Dakota. (p. 820) 6-9-Baculites sweetgrassensis Cobban, n. sp. 6, 7, Lateral and ventral views of paratype; 8, 9, lateral and ventral views of holotype. Colorado shale, 5.5 miles south of Shelby, Toole County, Montana. (p. 820) 10-12-Baculites mariasensis Cobban, n. sp. 10, 11, Lateral views of paratypes; 12, lateral view of holotype. Colorado shale, 5.5 miles south of Shelby, Toole County, Montana. (p. 818)",
    openalex = "W2528031705"
}

Baculites scotti, new species, marks a in the Upper Cretaceous Pierre and Bearpaw formations between the zones of B. gregoryensis and B. compressus. B. eliasi, new species, marks a between the zones of B. compressus and B. grandis. Both new species are common in Montana, Wyoming, Colorado, and South Dakota. HE Pierre shale of Late Cretaceous age contains two undescribed species of Baculites that are abundant at many localities in Montana, Wyoming, Colorado, and South Dakota and for which names are needed. The new species, Baculites scotti and B. eliasi, add refinement to the sequence of baculite zones originally defined by Cobban in 1951 (p. 817) and further refined by Cobban & Reeside in 1952 (p. 1020-1022). In the sequence of baculites established in 1951 B. scotti lies between the zones of B. gregoryensis and B. compressus, and B. eliasi lies between the zones of B. compressus and B. grandis. Cobban & Reeside (1952, p. 1021, 1022) noted that the of B. compressus could be divided into five subzones. The uppermost of these, the one marked by an unnamed form with stout cross section and smooth venter, is the of the new species B. eliasi. In terms of the standard stages of the Cretaceous, Baculites scotti and B. eliasi lie somewhere in the upper Campanian or in the lower Maestrichtian. Both species are younger than rocks that contain Scaphites spiniger Schliiter, a well known index fossil for the upper Campanian of northern Europe. However, both of the baculites are older than rocks that contain a species close to if not identical to Hoploscaphites constrictus (Sowerby), a form commonly accepted as guide fossil to the Maestrichtian stage in Europe. Types of the new species are deposited in the United States National Museum, Washington. Publication is authorized by the Director, U. S. Geological Survey. Class CEPHALOPODA Order AMMONOIDEA Family BACULITIDAE Meek, 1876 BACULITES SCOTTI Cobban n. sp. P1. 90, figs. 1-9; Text-figs. la-e,h Diagnosis.-This species, about average size for the genus, is characterized by its small degree of taper and by its suture with the first lateral lobe constricted just above the major lateral branches. Most specimens have smooth flanks and nearly smooth venters; a few individuals have broad nodelike ribs on the flanks spaced about one shell diameter apart. Many specimens have a ventrolateral depression that parallels the venter. Name.-The species is named for Glenn R. Scott of the U. S. Geological Survey whose investigations of the Pierre shale have added much to our knowledge of the stratigraphy and faunal zonation. Material.--The collection from which the types were selected consists of 230 baculites from the tepee zone of Gilbert (1897, p. 3) in the Pierre shale at Baculite Mesa five miles northeast of Pueblo at U.S.G.S. Mesozoic locality D84 in the NWsec. 10, T. 20 S., R. 64 W., Pueblo County, Colorado. Two other large collections of baculites were studied also. One lot consists of 154 specimens from a slightly lower level in the Pierre shale at U.S.G.S. Mesozoic locality D715 about 4.5 miles northeast of Pueblo in the SE? sec. 15, T. 20 S., R. 64 W. The other lot consists of 131 baculites from the Pierre shale at U.S.G.S. Mesozoic locality D901 on the west bank of Beaver Creek about 5 miles southeast of Buffalo Gap near the center of sec. 22, T. 7 S., R. 7 E., Fall River

@article{openalexw2343813256,
    author = "Cobban, W. A.",
    title = "Two new species of Baculites from the western interior region",
    year = "1958",
    journal = "Journal of Paleontology",
    abstract = "Baculites scotti, new species, marks a in the Upper Cretaceous Pierre and Bearpaw formations between the zones of B. gregoryensis and B. compressus. B. eliasi, new species, marks a between the zones of B. compressus and B. grandis. Both new species are common in Montana, Wyoming, Colorado, and South Dakota. HE Pierre shale of Late Cretaceous age contains two undescribed species of Baculites that are abundant at many localities in Montana, Wyoming, Colorado, and South Dakota and for which names are needed. The new species, Baculites scotti and B. eliasi, add refinement to the sequence of baculite zones originally defined by Cobban in 1951 (p. 817) and further refined by Cobban \& Reeside in 1952 (p. 1020-1022). In the sequence of baculites established in 1951 B. scotti lies between the zones of B. gregoryensis and B. compressus, and B. eliasi lies between the zones of B. compressus and B. grandis. Cobban \& Reeside (1952, p. 1021, 1022) noted that the of B. compressus could be divided into five subzones. The uppermost of these, the one marked by an unnamed form with stout cross section and smooth venter, is the of the new species B. eliasi. In terms of the standard stages of the Cretaceous, Baculites scotti and B. eliasi lie somewhere in the upper Campanian or in the lower Maestrichtian. Both species are younger than rocks that contain Scaphites spiniger Schliiter, a well known index fossil for the upper Campanian of northern Europe. However, both of the baculites are older than rocks that contain a species close to if not identical to Hoploscaphites constrictus (Sowerby), a form commonly accepted as guide fossil to the Maestrichtian stage in Europe. Types of the new species are deposited in the United States National Museum, Washington. Publication is authorized by the Director, U. S. Geological Survey. Class CEPHALOPODA Order AMMONOIDEA Family BACULITIDAE Meek, 1876 BACULITES SCOTTI Cobban n. sp. P1. 90, figs. 1-9; Text-figs. la-e,h Diagnosis.-This species, about average size for the genus, is characterized by its small degree of taper and by its suture with the first lateral lobe constricted just above the major lateral branches. Most specimens have smooth flanks and nearly smooth venters; a few individuals have broad nodelike ribs on the flanks spaced about one shell diameter apart. Many specimens have a ventrolateral depression that parallels the venter. Name.-The species is named for Glenn R. Scott of the U. S. Geological Survey whose investigations of the Pierre shale have added much to our knowledge of the stratigraphy and faunal zonation. Material.--The collection from which the types were selected consists of 230 baculites from the tepee zone of Gilbert (1897, p. 3) in the Pierre shale at Baculite Mesa five miles northeast of Pueblo at U.S.G.S. Mesozoic locality D84 in the NWsec. 10, T. 20 S., R. 64 W., Pueblo County, Colorado. Two other large collections of baculites were studied also. One lot consists of 154 specimens from a slightly lower level in the Pierre shale at U.S.G.S. Mesozoic locality D715 about 4.5 miles northeast of Pueblo in the SE? sec. 15, T. 20 S., R. 64 W. The other lot consists of 131 baculites from the Pierre shale at U.S.G.S. Mesozoic locality D901 on the west bank of Beaver Creek about 5 miles southeast of Buffalo Gap near the center of sec. 22, T. 7 S., R. 7 E., Fall River",
    openalex = "W2343813256",
    references = "doi101130001676061952631011cotcfo20co2, openalexw2528031705"
}

@article{peterson1958rebound,
    author = "PETERSON, R.",
    title = "REBOUND IN THE BEARPAW SHALE, WESTERN CANADA",
    year = "1958",
    journal = "Geological Society of America Bulletin",
    url = "https://doi.org/10.1130/0016-7606(1958)69[1113:ritbsw]2.0.co;2",
    doi = "10.1130/0016-7606(1958)69[1113:ritbsw]2.0.co;2",
    number = "9",
    pages = "1113",
    volume = "69"
}

ABSTRACT The marine Pierre shale, of Late Cretaceous age, on the northern and western flanks of the Black Hills, consists of dark gray shale with some sandy shale and sandstone, and many beds of bentonite. It ranges in thickness from 2,000 to 2,700 feet. In this area the Pierre shale may be divided into several members on the basis of lithologic differences in the shale and the presence of sandy and bentonitic units. In ascending order, these are the Gammon ferruginous member (including the Groat sandstone bed), the Mitten black shale member, and an unnamed upper part that consists of half or more of the formation. This upper part is chiefly dark gray shale but contains at the base a gray silty shale unit and near the top the Monument Hill and Kara bentonitic members. Studies in progress by Cobban reveal at least 16 ammonite zones in the Pierre shale on the western flank of the Black Hills.

@article{doi1013060bda5c3f16bd11d78645000102c1865d,
    author = "Robinson, Charles Sherwood and Mapel, W. J. and Cobban, W. A.",
    title = "Pierre Shale Along Western and Northern Flanks of Black Hills, Wyoming and Montana",
    year = "1959",
    journal = "AAPG Bulletin",
    abstract = "ABSTRACT The marine Pierre shale, of Late Cretaceous age, on the northern and western flanks of the Black Hills, consists of dark gray shale with some sandy shale and sandstone, and many beds of bentonite. It ranges in thickness from 2,000 to 2,700 feet. In this area the Pierre shale may be divided into several members on the basis of lithologic differences in the shale and the presence of sandy and bentonitic units. In ascending order, these are the Gammon ferruginous member (including the Groat sandstone bed), the Mitten black shale member, and an unnamed upper part that consists of half or more of the formation. This upper part is chiefly dark gray shale but contains at the base a gray silty shale unit and near the top the Monument Hill and Kara bentonitic members. Studies in progress by Cobban reveal at least 16 ammonite zones in the Pierre shale on the western flank of the Black Hills.",
    url = "https://doi.org/10.1306/0bda5c3f-16bd-11d7-8645000102c1865d",
    doi = "10.1306/0bda5c3f-16bd-11d7-8645000102c1865d",
    openalex = "W2146065965",
    references = "doi101130001676061952631011cotcfo20co2, doi103133mf36, doi103133pp154d, openalexw1596211625, openalexw2223743326, openalexw2343813256, openalexw2889759357"
}

@article{cobban1962new1,
    author = "Cobban, W. A",
    title = "New Baculites from the Bearpaw Shale and equivalent rocks of the western interior",
    year = "1962",
    journal = "Journal of Paleontology, v. 36, p. 126-135",
    note = "talkorigins\_source = {true}; raw\_reference = {Cobban, W. A., 1962, New Baculites from the Bearpaw Shale and equivalent rocks of the western interior: Journal of Paleontology, v. 36, p. 126-135.}"
}

New species of baculites described from Montana include Baculites cuneatus and B. jenseni from the Bearpaw shale [Cretaceous] and B. rugosus from the Pierre Shale [Cretaceous]. Baculites compressus Say var. ornatus Robinson is renamed B. compressus Say Say subsp. robinsoni. These baculites have suture patterns similar to that of B. compressus Say in that the terminal branches of the first lateral lobe are constricted at their base. The sequence of baculites having this type of a suture are, from oldest to youngest, B. pseudovatus Elias, B. crickmayi Williams, B. rugosus n.sp., B. corrugatus Elias, B. compressus Say and B. compressus subsp. robinsoni, B. cuneatus n.sp., B. reesidei Elias, B. jenseni n.sp., and B. eliasi Cobban.

@article{openalexw2510542759,
    author = "Cobban, W. A.",
    title = "New baculites from the Bearpaw shale and equivalent rocks of the Western Interior",
    year = "1962",
    journal = "Journal of Paleontology",
    abstract = "New species of baculites described from Montana include Baculites cuneatus and B. jenseni from the Bearpaw shale [Cretaceous] and B. rugosus from the Pierre Shale [Cretaceous]. Baculites compressus Say var. ornatus Robinson is renamed B. compressus Say Say subsp. robinsoni. These baculites have suture patterns similar to that of B. compressus Say in that the terminal branches of the first lateral lobe are constricted at their base. The sequence of baculites having this type of a suture are, from oldest to youngest, B. pseudovatus Elias, B. crickmayi Williams, B. rugosus n.sp., B. corrugatus Elias, B. compressus Say and B. compressus subsp. robinsoni, B. cuneatus n.sp., B. reesidei Elias, B. jenseni n.sp., and B. eliasi Cobban.",
    url = "https://openalex.org/W2510542759",
    openalex = "W2510542759",
    references = "doi101017cbo9781139567411, doi1013060bda5c3f16bd11d78645000102c1865d, doi1013063d932a1e16b111d78645000102c1865d, doi103133pp151, openalexw2343813256, openalexw2468477906"
}

@article{wulf1964shoestring,
    author = "Wulf, George R.",
    title = "Shoestring Sandstones in Cretaceous Bearpaw Shale in Central Montana: GEOLOGICAL NOTES",
    year = "1964",
    journal = "AAPG Bulletin",
    url = "https://doi.org/10.1306/bc743d87-16be-11d7-8645000102c1865d",
    doi = "10.1306/bc743d87-16be-11d7-8645000102c1865d",
    number = "7",
    pages = "1196-1198",
    volume = "48"
}

Reconnaissance examination of widely scattered outcrops of Upper Cretaceous rocks in the heavily glaciated areas of eastern North Dakota provides the basis for the first formal subdivision of the Pierre Shale in these areas. Five distinct units are present which can be related by both lithology and fossil content to equivalent units in the type Pierre Shale of central South Dakota and to units in the Vermilion River and Riding Mountain Formations of Manitoba. Existing stratigraphic names in current usage in Manitoba and central South Dakota are applied to four of the five members of the Pierre recognized in North Dakota. The Manitoba name Pembina is applied to the basal member of the Pierre, and the South Dakota names Gregory Member and DeGrey Member have been assigned to the two succeeding younger members. The Manitoba name Odanah is assigned to the hard siliceous shale that overlies the DeGrey Member. The fifth and youngest member of the Pierre Shale exposed in eastern North Dakota remains unnamed because of a lack of adequate stratigraphic and faunal data.

@article{doi103133pp392a,
    author = "Gill, James R. and Cobban, W. A.",
    title = "Stratigraphy of the Pierre Shale, Valley City and Pembina Mountain areas, North Dakota",
    year = "1965",
    journal = "USGS professional paper",
    abstract = "Reconnaissance examination of widely scattered outcrops of Upper Cretaceous rocks in the heavily glaciated areas of eastern North Dakota provides the basis for the first formal subdivision of the Pierre Shale in these areas. Five distinct units are present which can be related by both lithology and fossil content to equivalent units in the type Pierre Shale of central South Dakota and to units in the Vermilion River and Riding Mountain Formations of Manitoba. Existing stratigraphic names in current usage in Manitoba and central South Dakota are applied to four of the five members of the Pierre recognized in North Dakota. The Manitoba name Pembina is applied to the basal member of the Pierre, and the South Dakota names Gregory Member and DeGrey Member have been assigned to the two succeeding younger members. The Manitoba name Odanah is assigned to the hard siliceous shale that overlies the DeGrey Member. The fifth and youngest member of the Pierre Shale exposed in eastern North Dakota remains unnamed because of a lack of adequate stratigraphic and faunal data.",
    url = "https://doi.org/10.3133/pp392a",
    doi = "10.3133/pp392a",
    openalex = "W438602353",
    references = "doi1013063d93345616b111d78645000102c1865d, doi1013065ceadb9016bb11d78645000102c1865d, doi103133i379, doi103133pp390, doi104095100522, doi104095101609, doi104095102024, doi104095104405"
}

The Pierre Shale gastropod faunas show a great similarity at almost all stratigrapliic levels over the whole of the western interior, from Colorado and Wyoming eastward to the Dakotas and eastern Montana. The equivalent Bearpaw Shale of Canada and Montana contains the same fauna. Aside from taxonomic uniformity, one consistent feature of the fauna is that the upper stratigraphic levels contain a greater abundance and diversity of gastropods than the lower stratigraphic levels. Compared to the overlying Fox Hills Sandstone there is a significant change, very few species being common to the.two formations, and many genera that are common in one formation are absent in the other.

@article{doi103133pp393b,
    author = "Sohl, Norman F.",
    title = "Upper Cretaceous gastropods from the Pierre Shale at Red Bird, Wyoming",
    year = "1967",
    journal = "USGS professional paper",
    abstract = "The Pierre Shale gastropod faunas show a great similarity at almost all stratigrapliic levels over the whole of the western interior, from Colorado and Wyoming eastward to the Dakotas and eastern Montana. The equivalent Bearpaw Shale of Canada and Montana contains the same fauna. Aside from taxonomic uniformity, one consistent feature of the fauna is that the upper stratigraphic levels contain a greater abundance and diversity of gastropods than the lower stratigraphic levels. Compared to the overlying Fox Hills Sandstone there is a significant change, very few species being common to the.two formations, and many genera that are common in one formation are absent in the other.",
    url = "https://doi.org/10.3133/pp393b",
    doi = "10.3133/pp393b",
    openalex = "W180654227",
    references = "doi101017cbo9781316143483, doi1010381421057a0, doi101130mem71p1, doi1013063d93302016b111d78645000102c1865d, doi1023071483846, doi103133pp331b, doi105962bhltitle19929, openalexw2281941053, openalexw3198721165, openalexw611150972"
}

During Late Cretaceous time a broad north-trending epicon tinental sea covered much of the western interior of North America and extended from the Gulf of Mexico to the Arctic Ocean. The sea was bounded on the west by a narrow, unstable, and constantly rising cordillera which extended from Central America to Alaska and which separated the sea from Pacific oceanic waters. The east margin of the sea was bounded by the low-lying stable platform of the central part of the United States.

@article{doi103133pp776,
    author = "Gill, James R. and Cobban, W. A.",
    title = "Stratigraphy and geologic history of the Montana group and equivalent rocks, Montana, Wyoming, and North and South Dakota",
    year = "1973",
    journal = "USGS professional paper",
    abstract = "During Late Cretaceous time a broad north-trending epicon tinental sea covered much of the western interior of North America and extended from the Gulf of Mexico to the Arctic Ocean. The sea was bounded on the west by a narrow, unstable, and constantly rising cordillera which extended from Central America to Alaska and which separated the sea from Pacific oceanic waters. The east margin of the sea was bounded by the low-lying stable platform of the central part of the United States.",
    url = "https://doi.org/10.3133/pp776",
    doi = "10.3133/pp776",
    openalex = "W2260629992",
    references = "doi101126science1463645723, doi101130001676061952631011cotcfo20co2, doi101130mem116p557, doi1013065d25cbb316c111d78645000102c1865d, doi1013065d25cc3f16c111d78645000102c1865d, doi10230725058187, doi103133pp239, doi1034194bullgguv566590, openalexw1518209863, openalexw657396478"
}

@misc{bryan1974numerical,
    author = "Bryan, J.B. and Burton, D.E. and Denny, M.D.",
    title = "Numerical studies of cratering in Bearpaw shale: two-dimensional results",
    year = "1974",
    url = "https://doi.org/10.2172/4252762",
    doi = "10.2172/4252762"
}

The Western Interior of the United States contains an important sequence of middle Cenomanian-late Turonian ammonites. Ammonites from the northern part of the Western Interior are mostly North Temperate forms, whereas those from the southern part are a mixture of Tethyan and North Temperate forms. The ammonite succession in the southern part can be more finely zoned than that of the northern part, and offers better possibilities for international correlation. In the zonation, the boundary between the middle and upper Cenomanian is placed at the top of the zone of Plesiacanthoceras aff. P. wyomingense. The top of the Cenomanian is drawn at the top of the zone of Neocardioceras juddii as recommended in a 1981 study by C. W. Wright and W. J. Kennedy. However, Mammites nodosoides, which occurs three zones higher, is usually regarded in Europe as basal Turonian, although Wright and Kennedy have now recognized a zone of Watinoceras coloradoense at the base, which lies below the zone of Mammites nodosoides. In the Western Interior, W. coloradoense is restricted to the zone of Vascoceras (Greenhornoceras) birchbyi, which is separated from the zone of Neocardioceras juddii by a zone of Pseudaspidoceras flexuosum. Inasmuch as the ammonites in the latter zone are closely related to those in the zone of V. birchbyi, a Turonian assignment seems best for the zone of P. flexuosum. Collignoniceras woollgari, which is widely distributed in Europe, Asia, and North America, is usually regarded as middle Turonian in a threefold division and late Turonian in a twofold division. I consider the species to mark the base of the middle Turonian. Where to place the top of the middle Turonian, however, is a problem. Inasmuch as the best fauna! break is at the top of the zone of Prionocyclus hyatti, that is where the boundary is placed in this report. Inoceramids in the zone of P. hyatti are characterized by forms having a radial depression like the middle Turonian Inoceramus hobetsensis of Japan. The top of the Turonian is designated here at the top of the zone of Prionocyclus quadratus. Fossils of this zone include inoceramids of the fiegei-dresdensis group, which in Europe have been considered either very late Turonian in age or very early Coniacian. Prionocyclus quadratus is the youngest species of a lineage of prionocyclids. This species is succeeded by Forresteria (Solgerites) of Coniacian Age.

@article{cobban1984midcretaceous,
    author = "Cobban, William A.",
    title = "Mid-Cretaceous ammonite zones, Western Interior, United States",
    year = "1984",
    journal = "Bulletin of the Geological Society of Denmark",
    abstract = "The Western Interior of the United States contains an important sequence of middle Cenomanian-late Turonian ammonites. Ammonites from the northern part of the Western Interior are mostly North Temperate forms, whereas those from the southern part are a mixture of Tethyan and North Temperate forms. The ammonite succession in the southern part can be more finely zoned than that of the northern part, and offers better possibilities for international correlation. In the zonation, the boundary between the middle and upper Cenomanian is placed at the top of the zone of Plesiacanthoceras aff. P. wyomingense. The top of the Cenomanian is drawn at the top of the zone of Neocardioceras juddii as recommended in a 1981 study by C. W. Wright and W. J. Kennedy. However, Mammites nodosoides, which occurs three zones higher, is usually regarded in Europe as basal Turonian, although Wright and Kennedy have now recognized a zone of Watinoceras coloradoense at the base, which lies below the zone of Mammites nodosoides. In the Western Interior, W. coloradoense is restricted to the zone of Vascoceras (Greenhornoceras) birchbyi, which is separated from the zone of Neocardioceras juddii by a zone of Pseudaspidoceras flexuosum. Inasmuch as the ammonites in the latter zone are closely related to those in the zone of V. birchbyi, a Turonian assignment seems best for the zone of P. flexuosum. Collignoniceras woollgari, which is widely distributed in Europe, Asia, and North America, is usually regarded as middle Turonian in a threefold division and late Turonian in a twofold division. I consider the species to mark the base of the middle Turonian. Where to place the top of the middle Turonian, however, is a problem. Inasmuch as the best fauna! break is at the top of the zone of Prionocyclus hyatti, that is where the boundary is placed in this report. Inoceramids in the zone of P. hyatti are characterized by forms having a radial depression like the middle Turonian Inoceramus hobetsensis of Japan. The top of the Turonian is designated here at the top of the zone of Prionocyclus quadratus. Fossils of this zone include inoceramids of the fiegei-dresdensis group, which in Europe have been considered either very late Turonian in age or very early Coniacian. Prionocyclus quadratus is the youngest species of a lineage of prionocyclids. This species is succeeded by Forresteria (Solgerites) of Coniacian Age.",
    url = "https://doi.org/10.37570/bgsd-1984-33-06",
    doi = "10.37570/bgsd-1984-33-06",
    pages = "71-89",
    volume = "33"
}

@article{crossref1984performance,
    title = "Performance of a shaft in weak rock (Bearpaw Shale)",
    year = "1984",
    journal = "International Journal of Rock Mechanics and Mining Sciences \& Geomechanics Abstracts",
    url = "https://doi.org/10.1016/0148-9062(84)90630-2",
    doi = "10.1016/0148-9062(84)90630-2",
    number = "6",
    pages = "234",
    volume = "21"
}

AssTRArcT-Four hundred twenty-five fossil decapods, preserved in apatite concretions, were collected from the Early Campanian Gammon Ferruginous Member of the Pierre Shale in Butte County, South Dakota. The fauna, confined to a 4.3 meter interval of rock and mapped over eight square kilometers, is dominated by the mud shrimp Protocallianassa russelli n. sp. (74.5% of decapod fauna), the crab Necrocarcinus davisi n. sp. (14.6%), and the lobster Hoploparia mickelsoni n. sp. (9.5%), but includes four other crabs: Dioratiopus hearttailensis n. sp. (1.2%), Raninella oaheensis Bishop, 1978 (0.5%), Xanthosia elegans occidentalis n. sp. (0.5%), and Rugafariusfredrichi n. gen., n. sp. (0.2%). This group of decapods is considered to be an assemblage, the Protocallianassa-Necrocarcinus-Hoploparia Assemblage, because of similarities to the Dakoticancer Assemblage in faunal characteristics, mode of preservation, and geographic and stratigraphic distribution. This assemblage predates the migration of Dakoticancer overanus Rathbun into the Western Interior and the consequent development of the Dakoticancer Assemblage, which contains descendents of taxa in the Protocallianassa-Necrocarcinus-Hoploparia Assemblage, repeatedly present in the Upper Pierre Shale.

@article{openalexw2186932079,
    author = "Bishop, Gale A.",
    title = "Fossil decapod crustaceans from the Gammon Ferruginous Member, Pierre Shale (early Campanian), Black Hills, South Dakota",
    year = "1985",
    journal = "Journal of Paleontology",
    abstract = "AssTRArcT-Four hundred twenty-five fossil decapods, preserved in apatite concretions, were collected from the Early Campanian Gammon Ferruginous Member of the Pierre Shale in Butte County, South Dakota. The fauna, confined to a 4.3 meter interval of rock and mapped over eight square kilometers, is dominated by the mud shrimp Protocallianassa russelli n. sp. (74.5\% of decapod fauna), the crab Necrocarcinus davisi n. sp. (14.6\%), and the lobster Hoploparia mickelsoni n. sp. (9.5\%), but includes four other crabs: Dioratiopus hearttailensis n. sp. (1.2\%), Raninella oaheensis Bishop, 1978 (0.5\%), Xanthosia elegans occidentalis n. sp. (0.5\%), and Rugafariusfredrichi n. gen., n. sp. (0.2\%). This group of decapods is considered to be an assemblage, the Protocallianassa-Necrocarcinus-Hoploparia Assemblage, because of similarities to the Dakoticancer Assemblage in faunal characteristics, mode of preservation, and geographic and stratigraphic distribution. This assemblage predates the migration of Dakoticancer overanus Rathbun into the Western Interior and the consequent development of the Dakoticancer Assemblage, which contains descendents of taxa in the Protocallianassa-Necrocarcinus-Hoploparia Assemblage, repeatedly present in the Upper Pierre Shale.",
    openalex = "W2186932079",
    references = "doi1013060bda5c3f16bd11d78645000102c1865d"
}

An examination of the distributions of ammonite shell morphotypes in the Western Interior Cretaceous Greenhorn Cyclothem suggests that the varied morphologies represented by this diverse group of organisms reflect mode of life and to some extent environmental conditions. Although most ammonites apparently ranged from shallow nearshore to deeper mid-basinal habitats in the Western Interior Seaway (maximum depth about 300 m), the distributions of certain morphotypes suggest depth-restriction. For example, compressed, disc-shaped, and heavily nodose forms generally indicate bottoms shallower than about 50 m. Also, structural and morphological shell features appear in some cases to facilitate relative depth interpretations. While pelagic ammonites were sensitive to salinity, temperature, and oxygenation within the water column, nektobenthic and benthic ones may be useful indicators of oxygenation closer to the substrate. Some morphotypes are represented solely by taxa restricted to specific thermal regimes, and their changing distributions may reflect migrations of major watermasses. The distribution patterns of most morphotypes suggest that post-mortem drift was generally not a major factor affecting ammonites of relatively shallow epicontinental seas.

@article{doi1023073514731,
    author = "Batt, Richard J.",
    title = "Ammonite Shell Morphotype Distributions in the Western Interior Greenhorn Sea and Some Paleoecological Implications",
    year = "1989",
    journal = "Palaios",
    abstract = "An examination of the distributions of ammonite shell morphotypes in the Western Interior Cretaceous Greenhorn Cyclothem suggests that the varied morphologies represented by this diverse group of organisms reflect mode of life and to some extent environmental conditions. Although most ammonites apparently ranged from shallow nearshore to deeper mid-basinal habitats in the Western Interior Seaway (maximum depth about 300 m), the distributions of certain morphotypes suggest depth-restriction. For example, compressed, disc-shaped, and heavily nodose forms generally indicate bottoms shallower than about 50 m. Also, structural and morphological shell features appear in some cases to facilitate relative depth interpretations. While pelagic ammonites were sensitive to salinity, temperature, and oxygenation within the water column, nektobenthic and benthic ones may be useful indicators of oxygenation closer to the substrate. Some morphotypes are represented solely by taxa restricted to specific thermal regimes, and their changing distributions may reflect migrations of major watermasses. The distribution patterns of most morphotypes suggest that post-mortem drift was generally not a major factor affecting ammonites of relatively shallow epicontinental seas.",
    url = "https://doi.org/10.2307/3514731",
    doi = "10.2307/3514731",
    openalex = "W2315447634"
}

Species of Baculites are important marker fossils in the Upper Cretaceous rocks of the Western Interior of the United States and provide indices for 20 of the 29 Campanian and Maastrichtian zones recognized by Cobban (in Gill and Cobban, 1966; Cobban, 1977). They often occur in rock-forming proportions (Gill and Cobban, 1966, Pl. 11, fig. 3) and are common up through the lower Maastrichtian Baculites clinolobatus zone. In the type area of the Fox Hills Formation in west-central South Dakota, B. clinolobatus is present in the lower part of the Mobridge Member of the Pierre Shale, but Baculites are rare or absent in the rest of the member as well as in the overlying Elk Butte Member that forms the uppermost part of the Pierre Shale (Waage, 1968, p. 50, 51, fig. 6). Only the diminutive Baculites columna Morton, 1834, has been noted from the succeeding Fox Hills Formation (Waage, 1968). The highest marine Cretaceous rocks of the Western Interior are characterized instead by Sphenodiscus and a range of scaphitid species (Hoploscaphites, Discoscaphites). It is therefore of some interest to describe, for the first time, the baculitids from the very high Cretaceous of the Western Interior. The material described below was collected from the Fox Hills Formation by N. L. Larson, P. L. Larson, and R. A. Farrar of the Black Hills Institute of Geological Research, Hill City, South Dakota. We are grateful to them for allowing us to describe this interesting collection. Specimens cited below are deposited in the collections of the Black Hills Institute (BHI) and in the U.S. National Museum of Natural History (USNM) in Washington, D.C.

@article{cobban1992the,
    author = "Cobban, W. A. and Kennedy, W. J.",
    title = "The last Western Interior Baculites from the Fox Hills Formation of South Dakota",
    year = "1992",
    journal = "Journal of Paleontology",
    abstract = "Species of Baculites are important marker fossils in the Upper Cretaceous rocks of the Western Interior of the United States and provide indices for 20 of the 29 Campanian and Maastrichtian zones recognized by Cobban (in Gill and Cobban, 1966; Cobban, 1977). They often occur in rock-forming proportions (Gill and Cobban, 1966, Pl. 11, fig. 3) and are common up through the lower Maastrichtian Baculites clinolobatus zone. In the type area of the Fox Hills Formation in west-central South Dakota, B. clinolobatus is present in the lower part of the Mobridge Member of the Pierre Shale, but Baculites are rare or absent in the rest of the member as well as in the overlying Elk Butte Member that forms the uppermost part of the Pierre Shale (Waage, 1968, p. 50, 51, fig. 6). Only the diminutive Baculites columna Morton, 1834, has been noted from the succeeding Fox Hills Formation (Waage, 1968). The highest marine Cretaceous rocks of the Western Interior are characterized instead by Sphenodiscus and a range of scaphitid species (Hoploscaphites, Discoscaphites). It is therefore of some interest to describe, for the first time, the baculitids from the very high Cretaceous of the Western Interior. The material described below was collected from the Fox Hills Formation by N. L. Larson, P. L. Larson, and R. A. Farrar of the Black Hills Institute of Geological Research, Hill City, South Dakota. We are grateful to them for allowing us to describe this interesting collection. Specimens cited below are deposited in the collections of the Black Hills Institute (BHI) and in the U.S. National Museum of Natural History (USNM) in Washington, D.C.",
    url = "https://doi.org/10.1017/s0022336000024550",
    doi = "10.1017/s0022336000024550",
    number = "4",
    openalex = "W2480629809",
    pages = "682-684",
    volume = "66",
    references = "doi101017s0016756800083710, doi10230725058187, doi1051091524324, doi105962bhltitle1740, openalexw2140418606, openalexw2469770493, openalexw2592545764, openalexw2797845562, openalexw3198721165, openalexw657396478"
}

Abstract If the base of the Maastrichtian Stage is placed at the first appearance ofthe belemnite Belemnella lanceolata in Western Europe, the boundary between the Campanian and Maastrichtian stages in the U.S. Western Interiormay lie between the zones of Baculites jenseni and Baculites eliasi. The B. jenseni Zone can be shown to be latest Campanian in age on the basis of the occurrence of Nostoceras (N.) hyatti Stephenson and Jeletzkytes nodosus (Owen), which range to the top of the Campanian in the well-dated Vistula Valley sequence in Poland, but disappear before the first appearance of B. lanceolata. So defined the numerical age of the Maastrichtian lies between 73.2 ± 0.7 and 70.1 ±0.7 Ma, based upon dates from high temperature chronometers in bentonites in the Western Interior.

@article{doi101017s0016756800019580,
    author = "Kennedy, William J. and Cobban, W. A. and Scott, G. R.",
    title = "Ammonite correlation of the uppermost Campanian of Western Europe, the U.S.Gulf Coast, Atlantic Seaboard and Western Interior, and the numerical age of the base of the Maastrichtian",
    year = "1992",
    journal = "Geological Magazine",
    abstract = "Abstract If the base of the Maastrichtian Stage is placed at the first appearance ofthe belemnite Belemnella lanceolata in Western Europe, the boundary between the Campanian and Maastrichtian stages in the U.S. Western Interiormay lie between the zones of Baculites jenseni and Baculites eliasi. The B. jenseni Zone can be shown to be latest Campanian in age on the basis of the occurrence of Nostoceras (N.) hyatti Stephenson and Jeletzkytes nodosus (Owen), which range to the top of the Campanian in the well-dated Vistula Valley sequence in Poland, but disappear before the first appearance of B. lanceolata. So defined the numerical age of the Maastrichtian lies between 73.2 ± 0.7 and 70.1 ±0.7 Ma, based upon dates from high temperature chronometers in bentonites in the Western Interior.",
    url = "https://doi.org/10.1017/s0016756800019580",
    doi = "10.1017/s0016756800019580",
    openalex = "W2012496954",
    references = "doi101007978940156861618, doi1010160016703783901205, doi1010160031018288900302, doi101029pa003i006p00757, doi101126science23547931156, doi101130mem111, doi1037570bgsd19843301, doi1037570bgsd19843319, doi105281zenodo15951033, openalexw1572213743, openalexw2281941053, openalexw2510542759"
}

ABSTRACT One almost complete mosasaur skeleton and much additional material from the Upper Cretaceous Bearpaw Formation of South Central Saskatchewan permits the first adequate description and diagnosis of Plioplatecarpus primaevus Russell. It possesses the following unique (within mosasaurs) characters: 11 maxillary teeth; a large shield-shaped septomaxilla forming a median internarial septum; a posterodorsally directed iliac process; and no obturator foramen. It can be distinguished from Plioplatecarpus marshi in the possession of a modest sized coracoid foramen, and both P. houzeaui and P. marshi in the possession of an unreduced presacral column of 30 vertebrae, all bearing functional zygapophyses, indicating that P. primaevus is the primitive sistergroup to these two taxa. Although extremely similar to UNO 8611-2, an unnamed specimen from Alabama, the lack of an eminence on the posterior surface of the quadrate shaft in the latter establishes UNO 8611-2 as the primitive sister group of P. primaevus + [P. houzeaui + P. marshi]. A quadrate eminence, long considered to be diagnostic of the genus, shows considerable variability in size and shape in P. primaevus, suggesting that it is not suitable as a specific diagnostic character. Other species of Plioplatecarpus (P. crassartus, P. depressus, “Platecarpus” somenensis, “Mosasaurus” scanicus, and undescribed species from Scabby Butte, Alberta and Anderson River, North West Territories), have not been sufficiently characterized to include in a phylogenetic analysis.

@article{doi10108002724634199610011357,
    author = "Holmes, Robert B.",
    title = "Plioplatecarpus primaevus (Mosasauridae) from the Bearpaw Formation (Campanian, Upper Cretaceous) of the North American Western Interior Seaway",
    year = "1996",
    journal = "Journal of Vertebrate Paleontology",
    abstract = "ABSTRACT One almost complete mosasaur skeleton and much additional material from the Upper Cretaceous Bearpaw Formation of South Central Saskatchewan permits the first adequate description and diagnosis of Plioplatecarpus primaevus Russell. It possesses the following unique (within mosasaurs) characters: 11 maxillary teeth; a large shield-shaped septomaxilla forming a median internarial septum; a posterodorsally directed iliac process; and no obturator foramen. It can be distinguished from Plioplatecarpus marshi in the possession of a modest sized coracoid foramen, and both P. houzeaui and P. marshi in the possession of an unreduced presacral column of 30 vertebrae, all bearing functional zygapophyses, indicating that P. primaevus is the primitive sistergroup to these two taxa. Although extremely similar to UNO 8611-2, an unnamed specimen from Alabama, the lack of an eminence on the posterior surface of the quadrate shaft in the latter establishes UNO 8611-2 as the primitive sister group of P. primaevus + [P. houzeaui + P. marshi]. A quadrate eminence, long considered to be diagnostic of the genus, shows considerable variability in size and shape in P. primaevus, suggesting that it is not suitable as a specific diagnostic character. Other species of Plioplatecarpus (P. crassartus, P. depressus, “Platecarpus” somenensis, “Mosasaurus” scanicus, and undescribed species from Scabby Butte, Alberta and Anderson River, North West Territories), have not been sufficiently characterized to include in a phylogenetic analysis.",
    url = "https://doi.org/10.1080/02724634.1996.10011357",
    doi = "10.1080/02724634.1996.10011357",
    openalex = "W2087438454",
    references = "doi103133pp392a"
}

Heteromorph ammonites of the families Nostoceratidae Hyatt, 1894, and Diplomoceratidae Spath, 1926, are common to abundant in sediments deposited in the western and central parts of the U.S. Western Interior Seaway during the early late Campanian. The indices of the successive zones of Didymoceras nebrascense (Meek and Hayden, 1856a) (oldest), Didymoceras stevensoni (Whitfield, 1877), Exiteloceras jenneyi camacki, n. subsp., Exiteloceras jenneyi jenneyi (Whitfield, 1877), and Didymoceras cheyennense (Meek and Hayden, 1856a) are revised, as are Nostoceras monotuberculatum Kennedy and Cobban, 1993a (D. nebrascense and D. stevensoni zones), Oxybeloceras crassum (Whitfield, 1877) (D. stevensoni and E. jenneyi zones), and Spiroxybeloceras meekanum (Whitfield, 1877) (D. cheyennense zone). Solenoceras elegans, n. sp. (D. stevensoni and E. jenneyi zones), Solenoceras bearpawense, n. sp. (D. nebrascense zone), and Solenoceras larimerense, n. sp. (E. jenneyi zone) are also described.

@article{doi1012060003009020002510001lcchaf20co2,
    author = "Kennedy, William J. and Landman, Neil H. and Cobban, W. A. and Scott, G. R.",
    title = "LATE CAMPANIAN (CRETACEOUS) HETEROMORPH AMMONITES FROM THE WESTERN INTERIOR OF THE UNITED STATES",
    year = "2000",
    journal = "Bulletin of the American Museum of Natural History",
    abstract = "Heteromorph ammonites of the families Nostoceratidae Hyatt, 1894, and Diplomoceratidae Spath, 1926, are common to abundant in sediments deposited in the western and central parts of the U.S. Western Interior Seaway during the early late Campanian. The indices of the successive zones of Didymoceras nebrascense (Meek and Hayden, 1856a) (oldest), Didymoceras stevensoni (Whitfield, 1877), Exiteloceras jenneyi camacki, n. subsp., Exiteloceras jenneyi jenneyi (Whitfield, 1877), and Didymoceras cheyennense (Meek and Hayden, 1856a) are revised, as are Nostoceras monotuberculatum Kennedy and Cobban, 1993a (D. nebrascense and D. stevensoni zones), Oxybeloceras crassum (Whitfield, 1877) (D. stevensoni and E. jenneyi zones), and Spiroxybeloceras meekanum (Whitfield, 1877) (D. cheyennense zone). Solenoceras elegans, n. sp. (D. stevensoni and E. jenneyi zones), Solenoceras bearpawense, n. sp. (D. nebrascense zone), and Solenoceras larimerense, n. sp. (E. jenneyi zone) are also described.",
    url = "https://doi.org/10.1206/0003-0090(2000)251<0001:lcchaf>2.0.co;2",
    doi = "10.1206/0003-0090(2000)251<0001:lcchaf>2.0.co;2",
    openalex = "W2173600375",
    references = "doi101007978147579153213, doi101017s0016756800083710, doi101130mem71p1, doi1023071483846, doi103931erara140013, doi105962bhltitle59826, openalexw1919763799, openalexw2140418606, openalexw2592545764, openalexw657396478"
}

The upper part of the Pierre Shale and Fox Hills Formation were deposited in the Late Cretaceous (Maastrichtian) Western Interior Seaway. They crop out in a belt that roughly parallels the Front Range of the Rocky Mountains from Douglas to Weld County, Colorado. These rocks consist of sandy shales and sandstones and are overlain by the nonmarine Laramie Formation. A sparse assemblage of ammonites is present consisting of Coahuilites sheltoni Böse, 1928, Sphenodiscus pleurisepta (Conrad, 1857), Trachybaculites sp. cf. T. columna (Morton, 1834), Hoploscaphites birkelundae Landman and Waage, 1993, Hoploscaphites sp. cf. H. birkelundae, Jeletzkytes dorfi Landman and Waage, 1993, and Jeletzkytes sp. cf. J. dorfi. Hoploscaphites birkelundae and Jeletzkytes dorfi define the H. birkelundae Zone in the Western Interior, which represents the lower part of the upper Maastrichtian. These rocks are thus equivalent in age to the Fox Hills Formation in Niobrara County, Wyoming, and older than the type Fox Hills Formation in north-central South Dakota. An analysis of the ratio of 87Sr/86Sr in a belemnite from this zone in Morgan County, Colorado, yields a value of 0.707790 ± 0.000008 (2-sigma SE), nearly identical to that of a bivalve from the same zone in Niobrara County, Wyoming (McArthur et al., 1994). The western shoreline of the seaway during the time of H. birkelundae extended as far west as northwestern Colorado and southwestern Wyoming.

@article{doi1012060003008220033880001aftupo20co2,
    author = "Landman, Neil H. and Cobban, W. A.",
    title = "Ammonites from the Upper Part of the Pierre Shale and Fox Hills Formation of Colorado",
    year = "2003",
    journal = "American Museum Novitates",
    abstract = "The upper part of the Pierre Shale and Fox Hills Formation were deposited in the Late Cretaceous (Maastrichtian) Western Interior Seaway. They crop out in a belt that roughly parallels the Front Range of the Rocky Mountains from Douglas to Weld County, Colorado. These rocks consist of sandy shales and sandstones and are overlain by the nonmarine Laramie Formation. A sparse assemblage of ammonites is present consisting of Coahuilites sheltoni Böse, 1928, Sphenodiscus pleurisepta (Conrad, 1857), Trachybaculites sp. cf. T. columna (Morton, 1834), Hoploscaphites birkelundae Landman and Waage, 1993, Hoploscaphites sp. cf. H. birkelundae, Jeletzkytes dorfi Landman and Waage, 1993, and Jeletzkytes sp. cf. J. dorfi. Hoploscaphites birkelundae and Jeletzkytes dorfi define the H. birkelundae Zone in the Western Interior, which represents the lower part of the upper Maastrichtian. These rocks are thus equivalent in age to the Fox Hills Formation in Niobrara County, Wyoming, and older than the type Fox Hills Formation in north-central South Dakota. An analysis of the ratio of 87Sr/86Sr in a belemnite from this zone in Morgan County, Colorado, yields a value of 0.707790 ± 0.000008 (2-sigma SE), nearly identical to that of a bivalve from the same zone in Niobrara County, Wyoming (McArthur et al., 1994). The western shoreline of the seaway during the time of H. birkelundae extended as far west as northwestern Colorado and southwestern Wyoming.",
    url = "https://doi.org/10.1206/0003-0082(2003)388<0001:aftupo>2.0.co;2",
    doi = "10.1206/0003-0082(2003)388<0001:aftupo>2.0.co;2",
    openalex = "W2176304172",
    references = "cobban1992the, doi1011300091761320010291055mctbsi20co2, openalexw3198721165"
}

Based on study of modern foraminifera, changes in test po-rosity of ancient planktic foraminiferal specimens may be interpreted to reflect primarily changes in water tempera-ture. To test this hypothesis, planktic foraminiferal porosity data (percent pore space per unit area) of Hedbergella del-rioensis from three localities in the Cretaceous Western In-terior basin were analyzed in the context of basin history (e.g., relative sea-level). These data record spatial and tem-poral changes in water masses at the average living depth of H. delrioensis. A significant increase in porosity between the upper Cenomanian M. mosbyense biozone and lower S. gracile biozone suggests an increase in water mass temper-ature, reflecting northward advection of a central core of warmer (less dense) water into the central seaway. The spread of this water mass toward the north, and laterally east and west, correlates with an independent record of ris-ing sea-level. In addition to this secular porosity trend, higher frequency fluctuations may reflect transient oceano-graphic events related to changes in sea-level or circulation. In this study, porosity measurement was improved utilizing a scanning electron microscope and image analysis soft-ware. The work confirms prior results that as few as five fo-raminifera are required to produce a statistical assessment of average sample porosity. Use of pore concentration (num-ber of pores per unit area), previously suggested as a tem-perature proxy, was not supported. The major interpretative contribution is a temporally precise record of spatial chang-es in Western Interior water masses.

@article{doi1016690883135120030180034pfpaaa20co2,
    author = "Fisher, Cynthia G. and Sageman, Brad and ASURE, S. E. and ACKER, B. and MAHAR, Z.",
    title = "Planktic Foraminiferal Porosity Analysis as a Tool for Paleoceanographic Reconstruction, Mid-Cretaceous Western Interior Sea",
    year = "2003",
    journal = "Palaios",
    abstract = "Based on study of modern foraminifera, changes in test po-rosity of ancient planktic foraminiferal specimens may be interpreted to reflect primarily changes in water tempera-ture. To test this hypothesis, planktic foraminiferal porosity data (percent pore space per unit area) of Hedbergella del-rioensis from three localities in the Cretaceous Western In-terior basin were analyzed in the context of basin history (e.g., relative sea-level). These data record spatial and tem-poral changes in water masses at the average living depth of H. delrioensis. A significant increase in porosity between the upper Cenomanian M. mosbyense biozone and lower S. gracile biozone suggests an increase in water mass temper-ature, reflecting northward advection of a central core of warmer (less dense) water into the central seaway. The spread of this water mass toward the north, and laterally east and west, correlates with an independent record of ris-ing sea-level. In addition to this secular porosity trend, higher frequency fluctuations may reflect transient oceano-graphic events related to changes in sea-level or circulation. In this study, porosity measurement was improved utilizing a scanning electron microscope and image analysis soft-ware. The work confirms prior results that as few as five fo-raminifera are required to produce a statistical assessment of average sample porosity. Use of pore concentration (num-ber of pores per unit area), previously suggested as a tem-perature proxy, was not supported. The major interpretative contribution is a temporally precise record of spatial chang-es in Western Interior water masses.",
    url = "https://doi.org/10.1669/0883-1351(2003)018<0034:pfpaaa>2.0.co;2",
    doi = "10.1669/0883-1351(2003)018<0034:pfpaaa>2.0.co;2",
    openalex = "W2099156607",
    references = "doi1013063d93302016b111d78645000102c1865d"
}

@article{doi101016jpalaeo200411016,
    author = "He, Shaoneng and Kyser, T. Kurtis and Caldwell, W. G. E.",
    title = "Paleoenvironment of the Western Interior Seaway inferred from δ18O and δ13C values of molluscs from the Cretaceous Bearpaw marine cyclothem",
    year = "2005",
    journal = "Palaeogeography Palaeoclimatology Palaeoecology",
    url = "https://doi.org/10.1016/j.palaeo.2004.11.016",
    doi = "10.1016/j.palaeo.2004.11.016",
    openalex = "W2055183231",
    references = "openalexw3198721165"
}

From the Introduction: This provisional table is based mainly on the molluscan fossil record of the central and northern parts of the Western Interior of the United States. Some of the ammonite zones are known in Europe, such as Watinoceras devonense, Collignoniceras woollgari, Prionocyclus germari, Scaphites hippocrepis, Didymoceras stevensoni, and Didymoceras cheyennense, whereas more than one-half of the inoceramid zones are known also in Europe. A few of the ammonite zones are known from only a few localities, but the diagnostic species may occur in abundance. Among these are the zones of Acanthoceras granerosense, A. bellense, Dunveganoceras problematicum, Burroceras clydense, Watinoceras devonense, Collignoniceras praecox, and Scaphites mariasensis. All fossils listed in the table are in the national collection housed in Building 810 at the Federal Center, Denver, Colorado

@article{doi103133ofr20061250,
    author = "Cobban, W. A. and Walaszczyk, Ireneusz and Obradovich, John D. and McKinney, Kevin C.",
    title = "A USGS Zonal Table for the Upper Cretaceous Middle Cenomanian--Maastrichtian of the Western Interior of the United States Based on Ammonites, Inoceramids, and Radiometric Ages",
    year = "2006",
    journal = "Antarctica A Keystone in a Changing World",
    abstract = "From the Introduction: This provisional table is based mainly on the molluscan fossil record of the central and northern parts of the Western Interior of the United States. Some of the ammonite zones are known in Europe, such as Watinoceras devonense, Collignoniceras woollgari, Prionocyclus germari, Scaphites hippocrepis, Didymoceras stevensoni, and Didymoceras cheyennense, whereas more than one-half of the inoceramid zones are known also in Europe. A few of the ammonite zones are known from only a few localities, but the diagnostic species may occur in abundance. Among these are the zones of Acanthoceras granerosense, A. bellense, Dunveganoceras problematicum, Burroceras clydense, Watinoceras devonense, Collignoniceras praecox, and Scaphites mariasensis. All fossils listed in the table are in the national collection housed in Building 810 at the Federal Center, Denver, Colorado",
    url = "https://doi.org/10.3133/ofr20061250",
    doi = "10.3133/ofr20061250",
    openalex = "W104781427",
    references = "doi101017s0016756800083710, doi10108000241160410006483, doi101127nos2419911, doi101130081372361235, doi1013063d93302016b111d78645000102c1865d, doi10130683d923ed16c711d78645000102c1865d, doi1037570bgsd19843306, doi105962bhltitle59826, openalexw1483032662, openalexw1600028952, openalexw2771306584"
}

Preface Acknowledgments Abbreviations 1. Introduction: An Ocean in Kansas? 2. Our Discovery of the Western Interior Sea 3. Invertebrates, Plants, and Trace Fossils 4. Sharks: Sharp Teeth and Shell Crushers 5. Fishes, Large and Small 6. Turtles: Leatherback Giants 7. Where the Elasmosaurs Roamed 8. Pliosaurs and Polycotylids 9. Enter the Mosasaurs 10. Pteranodons: Rulers of the Air 11. Feathers and Teeth 12. Dinosaurs? 13. The Big Picture Epilogue: Where Did It Go? References Index

@article{doi105860choice432812,
    title = "Oceans of Kansas: a natural history of the western interior sea",
    year = "2006",
    journal = "Choice Reviews Online",
    abstract = "Preface Acknowledgments Abbreviations 1. Introduction: An Ocean in Kansas? 2. Our Discovery of the Western Interior Sea 3. Invertebrates, Plants, and Trace Fossils 4. Sharks: Sharp Teeth and Shell Crushers 5. Fishes, Large and Small 6. Turtles: Leatherback Giants 7. Where the Elasmosaurs Roamed 8. Pliosaurs and Polycotylids 9. Enter the Mosasaurs 10. Pteranodons: Rulers of the Air 11. Feathers and Teeth 12. Dinosaurs? 13. The Big Picture Epilogue: Where Did It Go? References Index",
    url = "https://doi.org/10.5860/choice.43-2812",
    doi = "10.5860/choice.43-2812",
    openalex = "W305387059"
}

Within the Western Interior Basin of North America, hundreds of small carbonate mounds associated with Late Cretaceous hydrocarbon emissions or seeps form the most extensively distributed occurrence of fossil seep mounds that is known, the Tepee Buttes. Analysis of the stratigraphic literature for the basin reveals that Tepee Butte formation occurred intermittently over a 10‐m.yr. period within a narrowly restricted paleogeographic region. The modern geographic distribution of the Tepee Buttes is constrained roughly to between 101°30′ and 105°30′W longitude and ranges from the northern Black Hills southward into southern Colorado. Four discernible intervals of seep activity are identified over a time span of 10 m.yr., from late Middle Campanian (78.7 Ma) through the Early Maastrichtian (69.1 Ma). Comparisons of the paleobiogeography of the Tepee Buttes to subsurface structures, basinal subsidence patterns, and shoreline position indicate an association between mound formation, western shoreline migration, and changes in basin tectonics. Initiation of the Tepee Butte formation is concurrent with changes in the basin tectonics and the subsequent eastward shift of maximum subsidence and sediment deposition within the basin. Mound distribution is basinward of the loci of maximum subsidence and is inferred to delineate the forebulge region of the basin during the period of Tepee Butte formation. Each determined interval of mound formation can be tied to migration of the basin’s western shoreline, with mound formation starting at maximum transgressive phases and ending at maximum regressive phases. It is postulated that shoreline migration altered sediment loading across the basin, affecting the degree of flexure of the forebulge region and thus affecting hydrocarbons emissions and mound formation.

@article{doi101086650181,
    author = "Metz, Cheryl L.",
    title = "Tectonic Controls on the Genesis and Distribution of Late Cretaceous, Western Interior Basin Hydrocarbon‐Seep Mounds (Tepee Buttes) of North America",
    year = "2010",
    journal = "The Journal of Geology",
    abstract = "Within the Western Interior Basin of North America, hundreds of small carbonate mounds associated with Late Cretaceous hydrocarbon emissions or seeps form the most extensively distributed occurrence of fossil seep mounds that is known, the Tepee Buttes. Analysis of the stratigraphic literature for the basin reveals that Tepee Butte formation occurred intermittently over a 10‐m.yr. period within a narrowly restricted paleogeographic region. The modern geographic distribution of the Tepee Buttes is constrained roughly to between 101°30′ and 105°30′W longitude and ranges from the northern Black Hills southward into southern Colorado. Four discernible intervals of seep activity are identified over a time span of 10 m.yr., from late Middle Campanian (78.7 Ma) through the Early Maastrichtian (69.1 Ma). Comparisons of the paleobiogeography of the Tepee Buttes to subsurface structures, basinal subsidence patterns, and shoreline position indicate an association between mound formation, western shoreline migration, and changes in basin tectonics. Initiation of the Tepee Butte formation is concurrent with changes in the basin tectonics and the subsequent eastward shift of maximum subsidence and sediment deposition within the basin. Mound distribution is basinward of the loci of maximum subsidence and is inferred to delineate the forebulge region of the basin during the period of Tepee Butte formation. Each determined interval of mound formation can be tied to migration of the basin’s western shoreline, with mound formation starting at maximum transgressive phases and ending at maximum regressive phases. It is postulated that shoreline migration altered sediment loading across the basin, affecting the degree of flexure of the forebulge region and thus affecting hydrocarbons emissions and mound formation.",
    url = "https://doi.org/10.1086/650181",
    doi = "10.1086/650181",
    openalex = "W2076384625",
    references = "doi1012060003009020002510001lcchaf20co2, doi1013060bda5c3f16bd11d78645000102c1865d, doi103133pp186k, kennedy2000late"
}

One way the effects of both ecology and environment on species can be observed in the fossil record is as changes in geographical distribution and range size. The prevalence of competitive interactions and species replacements in the fossil record has long been investigated and many evolutionary perspectives, including those of Darwin, have emphasized the importance of competitive interactions that ultimately lead one species to replace another. However, evidence for such phenomena in the fossil record is not always manifest. Here we use new quantitative analytical techniques based on Geographical Information Systems and PaleoGIS tectonic reconstructions to consider this issue in greater detail. The abundant, well-preserved fossil marine vertebrates of the Late Cretaceous Western Interior Seaway of North America provide the component data for this study. Statistical analysis of distributional and range size changes in taxa confirms earlier ideas that the relative frequency of competitive replacement in the fossil record is limited to non-existent. It appears that typically, environmental gradients played the primary role in determining species distributions, with competitive interactions playing a more minor role.

@article{doi101098rspb20101617,
    author = "Myers, Corinne and Lieberman, Bruce S.",
    title = "Sharks that pass in the night: using Geographical Information Systems to investigate competition in the Cretaceous Western Interior Seaway",
    year = "2010",
    journal = "Proceedings of the Royal Society B Biological Sciences",
    abstract = "One way the effects of both ecology and environment on species can be observed in the fossil record is as changes in geographical distribution and range size. The prevalence of competitive interactions and species replacements in the fossil record has long been investigated and many evolutionary perspectives, including those of Darwin, have emphasized the importance of competitive interactions that ultimately lead one species to replace another. However, evidence for such phenomena in the fossil record is not always manifest. Here we use new quantitative analytical techniques based on Geographical Information Systems and PaleoGIS tectonic reconstructions to consider this issue in greater detail. The abundant, well-preserved fossil marine vertebrates of the Late Cretaceous Western Interior Seaway of North America provide the component data for this study. Statistical analysis of distributional and range size changes in taxa confirms earlier ideas that the relative frequency of competitive replacement in the fossil record is limited to non-existent. It appears that typically, environmental gradients played the primary role in determining species distributions, with competitive interactions playing a more minor role.",
    url = "https://doi.org/10.1098/rspb.2010.1617",
    doi = "10.1098/rspb.2010.1617",
    openalex = "W2149266562"
}

Scaphitid ammonites (scaphites) are common in the Upper Cretaceous Pierre Shale and Bearpaw Shale of the Western Interior of North America. We redescribe Hoploscaphites nodosus (Owen, 1852) and H. brevis (Meek, 1876) from the Baculites compressus–B. cuneatus zones of the upper Campanian. The types of both of these species were collected in the mid-19th century in what was then called Nebraska Territory, and included parts of present-day South Dakota, North Dakota, and Montana. Based on our present knowledge of the distribution of these species, the type material was probably collected from the B. compressus–B. cuneatus zones in the Pierre Shale at Sage Creek, a tributary of the Cheyenne River, Pennington County, South Dakota.Traditionally, the more robust, more coarsely ornamented scaphites (comprising the “nodosus group”) from the Pierre Shale and Bearpaw Shale were assigned to Jeletzkytes Riccardi, 1983, and the more slender, more finely ornamented scaphites were assigned to Hoploscaphites Nowak, 1911. However, our large collections of these scaphites from the Baculites compressus–B. cuneatus zones reveal a complete intergradation between the two morphological extremes, and for many specimens, the choice of genus is arbitrary. In addition, our studies of other biostratigraphic zones in the Pierre Shale and Bearpaw Shale reveal that cooccurring species of these two “genera” share more in common with each other than they do with congeneric species from other horizons. Furthermore, contrary to earlier assumptions, Jeletkytes is not endemic to the Western Interior Basin of North America and occurs, for example, in the U.S. Atlantic Coastal Plain and Europe. We thus provisionally treat Jeletzkytes as a junior subjective synonym of Hoploscaphites. This expanded definition of Hoploscaphites is consistent with present-day concepts of other scaphitid genera such as Discoscaphites Meek, 1876, and Trachyscaphites Cobban and Scott, 1964.In Hoploscaphites nodosus and H. brevis, the juvenile shell is planispirally coiled with a small umbilicus. The whorl section is initially depressed and becomes more compressed through ontogeny. The angle of the body chamber in juveniles is approximately two-thirds of a whorl. At the approach of maturity, the shell uncoils, forming a relatively long shaft and recurved hook. The ratio of whorl width to whorl height reaches a minimum value at midshaft. The apertural margin at maturity is constricted and terminates in a flared lip. Commonly, the last two or three septa, corresponding to the formation of the hook, are more closely spaced (approximated). These features indicate that the rate of growth decreased and eventually stopped at maturity (“morphogenetic countdown” associated with determinate growth). Both species of scaphites occur as dimorphs, which are referred to as macroconchs (presumably females) and microconchs (presumably males). In samples of specimens of the same species within a single concretion, macroconchs are approximately 20% larger than microconchs. In addition to size, dimorphs are distinguished by differences in shape, including the presence or absence of an umbilical bulge, the size of the umbilical diameter, the outline of the umbilical shoulder relative to that of the venter in side view, and the relative change in whorl height in passing from the mature phragmocone to the shaft of the body chamber.The holotype of Hoploscaphites nodosus, by monotypy, is UC 6381, the original of Scaphites nodosus Owen (1852: 581, pl. 8, fig. 4). Adults exhibit a range of variation in size, degree of compression, and coarseness of ornament. The exposed phragmocone occupies most of the coiled portion of the shell, and is approximately two-thirds of a whorl in angular length. Adults are large (LMAX averages 91.8 mm in macroconchs and 78.0 mm in microconchs) and ellipsoidal in side view, with a strongly recurved hook (apertural angle averages 73° in macroconchs). The ratio of whorl width to whorl heigh

@article{doi1012066591,
    author = "Landman, Neil H. and Kennedy, W. J. and Cobban, W. A. and Larson, Neal L.",
    title = "Scaphites of the “Nodosus Group” from the Upper Cretaceous (Campanian) of the Western Interior of North America",
    year = "2010",
    journal = "Bulletin of the American Museum of Natural History",
    abstract = "Scaphitid ammonites (scaphites) are common in the Upper Cretaceous Pierre Shale and Bearpaw Shale of the Western Interior of North America. We redescribe Hoploscaphites nodosus (Owen, 1852) and H. brevis (Meek, 1876) from the Baculites compressus–B. cuneatus zones of the upper Campanian. The types of both of these species were collected in the mid-19th century in what was then called Nebraska Territory, and included parts of present-day South Dakota, North Dakota, and Montana. Based on our present knowledge of the distribution of these species, the type material was probably collected from the B. compressus–B. cuneatus zones in the Pierre Shale at Sage Creek, a tributary of the Cheyenne River, Pennington County, South Dakota.Traditionally, the more robust, more coarsely ornamented scaphites (comprising the “nodosus group”) from the Pierre Shale and Bearpaw Shale were assigned to Jeletzkytes Riccardi, 1983, and the more slender, more finely ornamented scaphites were assigned to Hoploscaphites Nowak, 1911. However, our large collections of these scaphites from the Baculites compressus–B. cuneatus zones reveal a complete intergradation between the two morphological extremes, and for many specimens, the choice of genus is arbitrary. In addition, our studies of other biostratigraphic zones in the Pierre Shale and Bearpaw Shale reveal that cooccurring species of these two “genera” share more in common with each other than they do with congeneric species from other horizons. Furthermore, contrary to earlier assumptions, Jeletkytes is not endemic to the Western Interior Basin of North America and occurs, for example, in the U.S. Atlantic Coastal Plain and Europe. We thus provisionally treat Jeletzkytes as a junior subjective synonym of Hoploscaphites. This expanded definition of Hoploscaphites is consistent with present-day concepts of other scaphitid genera such as Discoscaphites Meek, 1876, and Trachyscaphites Cobban and Scott, 1964.In Hoploscaphites nodosus and H. brevis, the juvenile shell is planispirally coiled with a small umbilicus. The whorl section is initially depressed and becomes more compressed through ontogeny. The angle of the body chamber in juveniles is approximately two-thirds of a whorl. At the approach of maturity, the shell uncoils, forming a relatively long shaft and recurved hook. The ratio of whorl width to whorl height reaches a minimum value at midshaft. The apertural margin at maturity is constricted and terminates in a flared lip. Commonly, the last two or three septa, corresponding to the formation of the hook, are more closely spaced (approximated). These features indicate that the rate of growth decreased and eventually stopped at maturity (“morphogenetic countdown” associated with determinate growth). Both species of scaphites occur as dimorphs, which are referred to as macroconchs (presumably females) and microconchs (presumably males). In samples of specimens of the same species within a single concretion, macroconchs are approximately 20\% larger than microconchs. In addition to size, dimorphs are distinguished by differences in shape, including the presence or absence of an umbilical bulge, the size of the umbilical diameter, the outline of the umbilical shoulder relative to that of the venter in side view, and the relative change in whorl height in passing from the mature phragmocone to the shaft of the body chamber.The holotype of Hoploscaphites nodosus, by monotypy, is UC 6381, the original of Scaphites nodosus Owen (1852: 581, pl. 8, fig. 4). Adults exhibit a range of variation in size, degree of compression, and coarseness of ornament. The exposed phragmocone occupies most of the coiled portion of the shell, and is approximately two-thirds of a whorl in angular length. Adults are large (LMAX averages 91.8 mm in macroconchs and 78.0 mm in microconchs) and ellipsoidal in side view, with a strongly recurved hook (apertural angle averages 73° in macroconchs). The ratio of whorl width to whorl heigh",
    url = "https://doi.org/10.1206/659.1",
    doi = "10.1206/659.1",
    openalex = "W2157595576",
    references = "doi101007978140206806513, doi10100797894017963095, doi101016s001600323892229x, doi101038114085a0, doi101093nqs5vi146318i, doi101126science11282807, doi1012060003009020073031cfttbi20co2, doi1034194bullgguv566590, doi105281zenodo16219869, openalexw1561111624, openalexw2343813256, openalexw2510542759, openalexw2592545764, openalexw2751580477, openalexw2912219260, openalexw2937684811, openalexw657396478, openalexw821285779"
}

Evaluating the effects of diagenesis on the isotopic compositions of Sr, O, and C in marine carbonates is critical to their use as proxies in reconstructing information on the salinity, temperature and dissolved inorganic carbon of ancient oceans. We have analyzed a series of samples of mollusk shells from the Baculites compressus zone (late Campanian) of the Pierre Shale of South Dakota. Samples included outer shell material and septa of cephalopods collected inside and outside concretions. Preservation was evaluated using light microscopy, scanning electron microscopy (SEM), trace element analysis and X-ray diffraction. All of the material consists of aragonite based on X-ray diffraction. An SEM preservation index (PI) was established based on comparison of the microstructure of the fossil material with that of modern Nautilus. Excellent preservation (PI = 5) was characterized by well-defined nacreous plates with discrete, angular boundaries. In contrast, samples showing fused nacreous plates with indistinct boundaries were rated poor (PI = 1). 87 Sr/ 86 Sr ratios vary with preservation and average 0.707648 ±.000021 (n = 10) for excellent preservation (PI ≈ 5), 0.707615 ±.000028 (n = 5) for good preservation (PI ≈ 3), 0.707404 ±.000074 (n=7) for fair preservation (PI ≈ 2), and 0.707261 ±.000053 (n=8) for poor preservation (PI ≈ 1). These data suggest that as the quality of the preservation declines, the mean 87 Sr/ 86 Sr ratio decreases and the standard error of the mean increases. Oxygen and carbon isotope analyses of the same specimens also show decreases with preservation, and δ 18 O, δ 13 C and 87 Sr/ 86 Sr are well correlated, suggesting that these tracers are all altered as the PI decreases. The Sr/Ca ratio increases as preservation decreases, indicating that Sr is added to the shell material during diagenesis. In contrast, Mg/Ca shows no trend with preservation. If the increasing Sr concentration (and decreasing 87 Sr/ 86 Sr) of the shell material with decreasing preservation represents the addition of Sr to the shell during diagenesis, we calculate that the added Sr had 87 Sr/ 86 Sr ranging from 0.707582 to 0.707032. Potential sources of the added Sr include older marine carbonates and weathering of volcanic ash layers present in the shale. The mechanisms of alteration likely include epitaxial growth of strontianite on the original shell aragonite and isotopic exchange of C and O between alteration fluids and shell carbonate. We conclude that SEM preservation criteria are effective in screening shell material that records original isotopic values and that variations in Sr, O and C isotope composition in well-preserved material can be used to assess paleoenvironmental parameters, such as salinity and temperature. Our results also indicate that assessing preservation is a critical prerequisite to the determination of numerical ages of shell material using strontium isotope stratigraphy.

@article{doi10247502201001,
    author = "Cochran, J. Kirk and Kallenberg, K. and Landman, Neil H. and Harries, Peter J. and Weinreb, D. and Turekian, Karl K. and Beck, Aaron J. and Cobban, W. A.",
    title = "Effect of diagenesis on the Sr, O, and C isotope composition of late Cretaceous mollusks from the Western Interior Seaway of North America",
    year = "2010",
    journal = "American Journal of Science",
    abstract = "Evaluating the effects of diagenesis on the isotopic compositions of Sr, O, and C in marine carbonates is critical to their use as proxies in reconstructing information on the salinity, temperature and dissolved inorganic carbon of ancient oceans. We have analyzed a series of samples of mollusk shells from the Baculites compressus zone (late Campanian) of the Pierre Shale of South Dakota. Samples included outer shell material and septa of cephalopods collected inside and outside concretions. Preservation was evaluated using light microscopy, scanning electron microscopy (SEM), trace element analysis and X-ray diffraction. All of the material consists of aragonite based on X-ray diffraction. An SEM preservation index (PI) was established based on comparison of the microstructure of the fossil material with that of modern Nautilus. Excellent preservation (PI = 5) was characterized by well-defined nacreous plates with discrete, angular boundaries. In contrast, samples showing fused nacreous plates with indistinct boundaries were rated poor (PI = 1). 87 Sr/ 86 Sr ratios vary with preservation and average 0.707648 ±.000021 (n = 10) for excellent preservation (PI ≈ 5), 0.707615 ±.000028 (n = 5) for good preservation (PI ≈ 3), 0.707404 ±.000074 (n=7) for fair preservation (PI ≈ 2), and 0.707261 ±.000053 (n=8) for poor preservation (PI ≈ 1). These data suggest that as the quality of the preservation declines, the mean 87 Sr/ 86 Sr ratio decreases and the standard error of the mean increases. Oxygen and carbon isotope analyses of the same specimens also show decreases with preservation, and δ 18 O, δ 13 C and 87 Sr/ 86 Sr are well correlated, suggesting that these tracers are all altered as the PI decreases. The Sr/Ca ratio increases as preservation decreases, indicating that Sr is added to the shell material during diagenesis. In contrast, Mg/Ca shows no trend with preservation. If the increasing Sr concentration (and decreasing 87 Sr/ 86 Sr) of the shell material with decreasing preservation represents the addition of Sr to the shell during diagenesis, we calculate that the added Sr had 87 Sr/ 86 Sr ranging from 0.707582 to 0.707032. Potential sources of the added Sr include older marine carbonates and weathering of volcanic ash layers present in the shale. The mechanisms of alteration likely include epitaxial growth of strontianite on the original shell aragonite and isotopic exchange of C and O between alteration fluids and shell carbonate. We conclude that SEM preservation criteria are effective in screening shell material that records original isotopic values and that variations in Sr, O and C isotope composition in well-preserved material can be used to assess paleoenvironmental parameters, such as salinity and temperature. Our results also indicate that assessing preservation is a critical prerequisite to the determination of numerical ages of shell material using strontium isotope stratigraphy.",
    url = "https://doi.org/10.2475/02.2010.01",
    doi = "10.2475/02.2010.01",
    openalex = "W2120473822"
}

@article{palamarczuk2011dinoflagellate,
    author = "Palamarczuk, S. and Landman, N. H.",
    title = "Dinoflagellate cysts from the upper Campanian Pierre Shale and Bearpaw Shale of the U.S. Western Interior",
    year = "2011",
    journal = "Rocky Mountain Geology",
    url = "https://doi.org/10.2113/gsrocky.46.2.137",
    doi = "10.2113/gsrocky.46.2.137",
    number = "2",
    openalex = "W2137587758",
    pages = "137-164",
    volume = "46",
    references = "doi1010160031018289900187, doi1010160031018294900248, doi1010160377839894900140, doi101017s1477201908002538, doi101038274653a0, doi101130001676061952631011cotcfo20co2, doi1018814epiiugs2001v24i4002, doi10247502201001, doi1041386506, doi105281zenodo16578503, openalexw2510542759"
}

The northern part of the North American Western Interior Sedimentary Basin has yielded well-preserved terrestrial palynomorphs whose occurrences allow the biostratigraphic characterization of the basin. Data have been compiled from sections that in composite span the latest Turonian to Paleocene. These data allow for the identification of species that are biostratigraphically useful within Alberta and adjacent portions of the basin. Progress has been made in establishing a stable biostratigraphic context for the basin using the first and last occurrences of 103 taxa. These palynomorphs provide a refined chronostratigraphic framework when combined with radiometric ages, polarity chronologies and ammonite biozonations. This framework has allowed the intrabasinal correlation of widely distributed sections in the Alberta and Montana portion of the basin and can be applied to stratigraphic problems in the more northern portion of the Western Interior Basin.

@article{doi101080019161222011642127,
    author = "Braman, Dennis R. and Sweet, A R",
    title = "Biostratigraphically useful Late Cretaceous–Paleocene Terrestrial palynomorphs from the Canadian Western Interior Sedimentary Basin",
    year = "2012",
    journal = "Palynology",
    abstract = "The northern part of the North American Western Interior Sedimentary Basin has yielded well-preserved terrestrial palynomorphs whose occurrences allow the biostratigraphic characterization of the basin. Data have been compiled from sections that in composite span the latest Turonian to Paleocene. These data allow for the identification of species that are biostratigraphically useful within Alberta and adjacent portions of the basin. Progress has been made in establishing a stable biostratigraphic context for the basin using the first and last occurrences of 103 taxa. These palynomorphs provide a refined chronostratigraphic framework when combined with radiometric ages, polarity chronologies and ammonite biozonations. This framework has allowed the intrabasinal correlation of widely distributed sections in the Alberta and Montana portion of the basin and can be applied to stratigraphic problems in the more northern portion of the Western Interior Basin.",
    url = "https://doi.org/10.1080/01916122.2011.642127",
    doi = "10.1080/01916122.2011.642127",
    openalex = "W2014918293",
    references = "doi101006cres19941022, doi101139e72101, doi1013063d93302016b111d78645000102c1865d, doi1013063d93432e16b111d78645000102c1865d, doi103133pp392a"
}

Concretions are the most characteristic mode of fossil occurrence in the Upper Cretaceous Western Interior of the United States. An in-depth analysis of a single concretion from the upper Campanian Pierre Shale, South Dakota, drawing upon sedimentology, paleontology, shell preservation, degree of encrustation, and geochemistry allows us to determine a time frame for the accumulation and burial of the organisms and the process of cementation and diagenesis of the concretion. The concretion is very fossiliferous and dominated by mollusks. Large ammonites are commonly broken up with pieces missing from the adapical end of the body chamber. This breakage pattern is widely interpreted as evidence of lethal damage, implying introduction into the burial site via predation. In contrast, smaller ammonites are nearly complete and may have died due to smothering in resuspended sediment produced by bottom currents. The concretion is rich in cephalopod jaws, which mostly appear as isolated occurrences, usually deformed, with the calcite covering (aptychus) missing. The preservation of jaws suggests that the organic debris did not remain in the taphonomically active zone for more than a few years. The concretion, thus, represents a time-averaged deposit of organisms derived from the local community. In contrast, host sediments contain fewer fossils, most of which are crushed. Oxygen and carbon isotopic composition of samples in the concretion and the host sediments reveals a two-stage diagenetic history of the concretion. First, cementation probably occurred at shallow burial depths in early diagenesis in association with the decomposition of organic matter and the oxidation of methane. Second, alteration of the shelly material and the formation of calcite crystals filling the empty chambers of ammonites probably occurred during later diagenesis in contact with meteoric water.

@article{doi102110palo2011p11105r,
    author = "Landman, Neil H. and Klofak, Susan M.",
    title = "ANATOMY OF A CONCRETION: LIFE, DEATH, AND BURIAL IN THE WESTERN INTERIOR SEAWAY",
    year = "2012",
    journal = "Palaios",
    abstract = "Concretions are the most characteristic mode of fossil occurrence in the Upper Cretaceous Western Interior of the United States. An in-depth analysis of a single concretion from the upper Campanian Pierre Shale, South Dakota, drawing upon sedimentology, paleontology, shell preservation, degree of encrustation, and geochemistry allows us to determine a time frame for the accumulation and burial of the organisms and the process of cementation and diagenesis of the concretion. The concretion is very fossiliferous and dominated by mollusks. Large ammonites are commonly broken up with pieces missing from the adapical end of the body chamber. This breakage pattern is widely interpreted as evidence of lethal damage, implying introduction into the burial site via predation. In contrast, smaller ammonites are nearly complete and may have died due to smothering in resuspended sediment produced by bottom currents. The concretion is rich in cephalopod jaws, which mostly appear as isolated occurrences, usually deformed, with the calcite covering (aptychus) missing. The preservation of jaws suggests that the organic debris did not remain in the taphonomically active zone for more than a few years. The concretion, thus, represents a time-averaged deposit of organisms derived from the local community. In contrast, host sediments contain fewer fossils, most of which are crushed. Oxygen and carbon isotopic composition of samples in the concretion and the host sediments reveals a two-stage diagenetic history of the concretion. First, cementation probably occurred at shallow burial depths in early diagenesis in association with the decomposition of organic matter and the oxidation of methane. Second, alteration of the shelly material and the formation of calcite crystals filling the empty chambers of ammonites probably occurred during later diagenesis in contact with meteoric water.",
    url = "https://doi.org/10.2110/palo.2011.p11-105r",
    doi = "10.2110/palo.2011.p11-105r",
    openalex = "W2091098601",
    references = "doi101007978140206806513, doi1012066591, openalexw2768082911, palamarczuk2011dinoflagellate"
}

Time-dependent behaviour can have a significant influence on the compressibility characteristics of soils. However, most of the research on this topic has investigated the behaviour of soft soils. In this paper, the time-dependent behaviour of a hard clay shale (Bearpaw Shale) is investigated using both one-dimensional multi-staged loading (MSL) oedometer and constant rate of strain (CRS) oedometer consolidation tests conducted on 25.0 and 16.9 mm diameter specimens. The results show that soft clays and hard clay shales that share the same C αe /[Formula: see text] ratio (where C αe is the secondary compression index and [Formula: see text] is the incremental compression index) will show the same approximately 7% change in pre-consolidation pressure for an increase of one log cycle of strain rate despite the many orders of magnitude difference in pre-consolidation pressure. In the case of the Bearpaw Shale, this 7% change in pre-consolidation pressure corresponds to approximately 700 kPa. The time-dependent behaviour of the Bearpaw Shale during unloading (C αe /[Formula: see text], where [Formula: see text] is the incremental swelling index) was observed to follow a similar ratio to that observed in compression (C αe /[Formula: see text]). While the exact nature of the compression and swelling events that have occurred over the life of the Bearpaw Formation is not clear, the influence of secondary compression cannot be ignored for interpretation of the geological history of this deposit.

@article{powell2012timedependent,
    author = "Powell, J. Suzanne and Take, W. Andy and Siemens, Greg and Remenda, V.H.",
    title = "Time-dependent behaviour of the Bearpaw Shale in oedometric loading and unloading",
    year = "2012",
    journal = "Canadian Geotechnical Journal",
    abstract = "Time-dependent behaviour can have a significant influence on the compressibility characteristics of soils. However, most of the research on this topic has investigated the behaviour of soft soils. In this paper, the time-dependent behaviour of a hard clay shale (Bearpaw Shale) is investigated using both one-dimensional multi-staged loading (MSL) oedometer and constant rate of strain (CRS) oedometer consolidation tests conducted on 25.0 and 16.9 mm diameter specimens. The results show that soft clays and hard clay shales that share the same C αe /[Formula: see text] ratio (where C αe is the secondary compression index and [Formula: see text] is the incremental compression index) will show the same approximately 7\% change in pre-consolidation pressure for an increase of one log cycle of strain rate despite the many orders of magnitude difference in pre-consolidation pressure. In the case of the Bearpaw Shale, this 7\% change in pre-consolidation pressure corresponds to approximately 700 kPa. The time-dependent behaviour of the Bearpaw Shale during unloading (C αe /[Formula: see text], where [Formula: see text] is the incremental swelling index) was observed to follow a similar ratio to that observed in compression (C αe /[Formula: see text]). While the exact nature of the compression and swelling events that have occurred over the life of the Bearpaw Formation is not clear, the influence of secondary compression cannot be ignored for interpretation of the geological history of this deposit.",
    url = "https://doi.org/10.1139/t2012-004",
    doi = "10.1139/t2012-004",
    number = "4",
    pages = "427-441",
    volume = "49"
}

The cephalopods from Union y Progreso represent the first fossil assemblage described from the Parras Shale in Coahuila, Mexico. Pseudoschloenbachia (Pseudoschloenbachia) aff. P. (P.) mexicana (Renz, 1936), P. (P.) mexicana (Renz, 1936), Baculites haresi Reeside, 1927, and Menabites (Delawarella) vanuxemi (Morton, 1830) have a geographically restricted occurrence. Didymoceras juv. sp., Menuites juv. sp., Polyptychoceras juv. sp., Pseudoxybeloceras (Parasolenoceras) juv. sp., and Scaphites sp. ex gr. S. hippocrepis (DeKay, 1828) are represented by juveniles and could not be determined to species level. Desmophyllites diphylloides (Forbes, 1846) is the only long-ranging, cosmopolitan species described from this assemblage. Three new species are described: Eutrephoceras irritilasi n. sp., Hypophylloceras (Neophylloceras) arturoi n. sp., and Tetragonites silencioensis n. sp. The morphotype Baculites n. sp. is also inferred to be distinct. The faunal composition of this assemblage indicates a late early Campanian age. This assemblage shows a high degree of endemism. The causes for this endemism are currently unknown and difficult to assess. Nevertheless, the generic composition of the Union y Progreso ammonite assemblage suggests a short-term early Campanian endemic event.

@article{doi10166612123,
    author = "Ifrim, Christina and Stinnesbeck, Wolfgang and Ventura, José Flores",
    title = "An endemic cephalopod assemblage from the lower Campanian (Late Cretaceous) Parras Shale, western Coahuila, Mexico",
    year = "2013",
    journal = "Journal of Paleontology",
    abstract = "The cephalopods from Union y Progreso represent the first fossil assemblage described from the Parras Shale in Coahuila, Mexico. Pseudoschloenbachia (Pseudoschloenbachia) aff. P. (P.) mexicana (Renz, 1936), P. (P.) mexicana (Renz, 1936), Baculites haresi Reeside, 1927, and Menabites (Delawarella) vanuxemi (Morton, 1830) have a geographically restricted occurrence. Didymoceras juv. sp., Menuites juv. sp., Polyptychoceras juv. sp., Pseudoxybeloceras (Parasolenoceras) juv. sp., and Scaphites sp. ex gr. S. hippocrepis (DeKay, 1828) are represented by juveniles and could not be determined to species level. Desmophyllites diphylloides (Forbes, 1846) is the only long-ranging, cosmopolitan species described from this assemblage. Three new species are described: Eutrephoceras irritilasi n. sp., Hypophylloceras (Neophylloceras) arturoi n. sp., and Tetragonites silencioensis n. sp. The morphotype Baculites n. sp. is also inferred to be distinct. The faunal composition of this assemblage indicates a late early Campanian age. This assemblage shows a high degree of endemism. The causes for this endemism are currently unknown and difficult to assess. Nevertheless, the generic composition of the Union y Progreso ammonite assemblage suggests a short-term early Campanian endemic event.",
    url = "https://doi.org/10.1666/12-123",
    doi = "10.1666/12-123",
    openalex = "W2168179436",
    references = "doi1010160012825272900724, doi101017s0016756800083710, doi101038061608a0, doi10108000359192209519274, doi101144transgslb797, doi105962bhltitle11582, doi105962bhltitle1740, doi105962bhltitle59826, openalexw2510542759, openalexw566313317, openalexw657396478"
}

Abstract The Western Interior Seaway (WIS) was a shallow and expansive body of water that covered the central United States during the Late Cretaceous. Attempts to reconstruct temperatures in the seaway using the oxygen isotopic composition of biogenic carbonates have suffered from uncertainty in the oxygen isotopic composition of seawater (δ18Ow) in the semi-restricted basin. We present new reconstructed temperature and δ18Ow data from marine and estuarine environments in the WIS and freshwater environments in WIS source rivers, derived from clumped isotope analyses of bivalve and gastropod shells. We find temperatures of 5–21 °C, δ18Ow values below contemporaneous Gulf of Mexico marine sites, and a strong correlation between δ18Ow and environmental setting. We propose that decreasing δ18Ow values reflect decreasing salinity driven by an increasing contribution of continental runoff. Using a two-end-member salinity-δ18Ow mixing model, we estimate salinities of 29–35 psu (practical salinity units) for the deep marine, 20–32 psu for the shallow marine, and 11–26 psu for the estuarine environments of the WIS. New climate model simulations agree with reconstructed temperatures and salinities and suggest the presence of salinity driven stratification within the seaway.

@article{doi101130g383111,
    author = "Petersen, Sierra and Tabor, Clay and Lohmann, Kyger C. and Poulsen, Christopher J. and Meyer, Kyle W. and Carpenter, Scott J. and Erickson, J. Mark and Matsunaga, Kelly K. S. and Smith, Selena Y. and Sheldon, Nathan D.",
    title = "Temperature and salinity of the Late Cretaceous Western Interior Seaway",
    year = "2016",
    journal = "Geology",
    abstract = "Abstract The Western Interior Seaway (WIS) was a shallow and expansive body of water that covered the central United States during the Late Cretaceous. Attempts to reconstruct temperatures in the seaway using the oxygen isotopic composition of biogenic carbonates have suffered from uncertainty in the oxygen isotopic composition of seawater (δ18Ow) in the semi-restricted basin. We present new reconstructed temperature and δ18Ow data from marine and estuarine environments in the WIS and freshwater environments in WIS source rivers, derived from clumped isotope analyses of bivalve and gastropod shells. We find temperatures of 5–21 °C, δ18Ow values below contemporaneous Gulf of Mexico marine sites, and a strong correlation between δ18Ow and environmental setting. We propose that decreasing δ18Ow values reflect decreasing salinity driven by an increasing contribution of continental runoff. Using a two-end-member salinity-δ18Ow mixing model, we estimate salinities of 29–35 psu (practical salinity units) for the deep marine, 20–32 psu for the shallow marine, and 11–26 psu for the estuarine environments of the WIS. New climate model simulations agree with reconstructed temperatures and salinities and suggest the presence of salinity driven stratification within the seaway.",
    url = "https://doi.org/10.1130/g38311.1",
    doi = "10.1130/g38311.1",
    openalex = "W2519621656",
    references = "doi103133pp776"
}

Plesiosauria is a diverse clade of marine reptiles that have been studied since the early 19th century. However, phylogenetic relationships within the group have been contentious due to limited taxon sampling and a misunderstanding of how ontogeny, interspecific and intraspecific variation affect character states. This is particularly true for elasmosaurids, a Cretaceous clade of long-necked plesiosaurians. In 2010, a new, nearly complete skeleton, MOR 3072, was collected from the Late Cretaceous (Campanian–Maastrichtian) Bearpaw Shale of northeast Montana. The specimen provides detailed morphological information rarely observed within Elasmosauridae, including a complete skull, the anterior 23 cervical vertebrae, a partial dorsal and caudal vertebral column, incomplete pectoral and pelvic girdles, elements of both fore- and hind limbs, ribs, and gastralia. Being early Maastrichtian in age, MOR 3072 is the stratigraphically youngest elasmosaurid known from the Western Interior Seaway, and is recognized as a new genus and species, Nakonanectes bradti. We present a description of N. bradti and conduct an extended phylogenetic analysis of Elasmosauridae. N. bradti is found to be deeply-nested within the clade of large-bodied, long-necked, Western Interior Styxosaurinae. However, MOR 3072 is one of the smallest adult elasmosaurids ever recovered (5.1–5.6 m) and exhibits a reduced neck length compared to other North American elasmosaurids, resulting from a reduction in both centrum length and number of cervical vertebrae (39–42 were originally present). These features are convergent with the Southern Hemisphere clade of short-necked Maastrichtian elasmosaurids, Aristonectinae, and demonstrate multiple origins of shortnecked body proportions from longer-necked ancestors within Elasmosauridae.

@article{doi1010800272463420171278608,
    author = "Serratos, Danielle J. and Druckenmiller, Patrick S. and Benson, Roger",
    title = "A new elasmosaurid (sauropterygia, plesiosauria) from the bearpaw shale (late cretaceous, maastrichtian) of montana demonstrates multiple evolutionary reductions of neck length within elasmosauridae",
    year = "2017",
    journal = "Journal of Vertebrate Paleontology",
    abstract = "Plesiosauria is a diverse clade of marine reptiles that have been studied since the early 19th century. However, phylogenetic relationships within the group have been contentious due to limited taxon sampling and a misunderstanding of how ontogeny, interspecific and intraspecific variation affect character states. This is particularly true for elasmosaurids, a Cretaceous clade of long-necked plesiosaurians. In 2010, a new, nearly complete skeleton, MOR 3072, was collected from the Late Cretaceous (Campanian–Maastrichtian) Bearpaw Shale of northeast Montana. The specimen provides detailed morphological information rarely observed within Elasmosauridae, including a complete skull, the anterior 23 cervical vertebrae, a partial dorsal and caudal vertebral column, incomplete pectoral and pelvic girdles, elements of both fore- and hind limbs, ribs, and gastralia. Being early Maastrichtian in age, MOR 3072 is the stratigraphically youngest elasmosaurid known from the Western Interior Seaway, and is recognized as a new genus and species, Nakonanectes bradti. We present a description of N. bradti and conduct an extended phylogenetic analysis of Elasmosauridae. N. bradti is found to be deeply-nested within the clade of large-bodied, long-necked, Western Interior Styxosaurinae. However, MOR 3072 is one of the smallest adult elasmosaurids ever recovered (5.1–5.6 m) and exhibits a reduced neck length compared to other North American elasmosaurids, resulting from a reduction in both centrum length and number of cervical vertebrae (39–42 were originally present). These features are convergent with the Southern Hemisphere clade of short-necked Maastrichtian elasmosaurids, Aristonectinae, and demonstrate multiple origins of shortnecked body proportions from longer-necked ancestors within Elasmosauridae.",
    url = "https://doi.org/10.1080/02724634.2017.1278608",
    doi = "10.1080/02724634.2017.1278608",
    openalex = "W2607396504",
    references = "doi101080027246342012658124, palamarczuk2011dinoflagellate"
}

We report the discovery of lower jaws of Baculites (Ammonoidea) from the Upper Cretaceous U.S. Western Interior. In the lower Campanian Smoky Hill Chalk Member of the Niobrara Chalk of Kansas, most of the jaws occur as isolated elements. Based on their age, they probably belong to Baculites sp. (smooth). They conform to the description of rugaptychus, and are ornamented with coarse rugae on their ventral side. One specimen is preserved inside a small fecal pellet that was probably produced by a fish. Another specimen occurs inside in a crushed body chamber near the aperture and is probably in situ. Three small structures are present immediately behind the jaw and may represent the remains of the gills. In the lower Maastrichtian Pierre Shale of Wyoming, two specimens of Baculites grandis contain lower jaws inside their body chambers, and are probably in situ. In both specimens, the jaws are oriented at an acute angle to the long axis of the shell, with their anterior ends pointing toward the dorsum. One of the jaws is folded into a U-shape, which probably approximates the shape of the jaw during life. Based on the measurements of the jaws and the shape of the shell, the jaws could not have touched the sides of the shell even if they were splayed out, implying that they could not have effectively served as opercula. Instead, in combination with the upper jaws and radula, they constituted the buccal apparatus that collected and conveyed food to the esophagus.

@article{larson2017description,
    author = "Larson, Neal L. and Landman, Neil H.",
    title = "Description of the lower jaws of Baculites from the Upper Cretaceous U.S. Western Interior",
    year = "2017",
    journal = "Acta Geologica Polonica",
    abstract = "We report the discovery of lower jaws of Baculites (Ammonoidea) from the Upper Cretaceous U.S. Western Interior. In the lower Campanian Smoky Hill Chalk Member of the Niobrara Chalk of Kansas, most of the jaws occur as isolated elements. Based on their age, they probably belong to Baculites sp. (smooth). They conform to the description of rugaptychus, and are ornamented with coarse rugae on their ventral side. One specimen is preserved inside a small fecal pellet that was probably produced by a fish. Another specimen occurs inside in a crushed body chamber near the aperture and is probably in situ. Three small structures are present immediately behind the jaw and may represent the remains of the gills. In the lower Maastrichtian Pierre Shale of Wyoming, two specimens of Baculites grandis contain lower jaws inside their body chambers, and are probably in situ. In both specimens, the jaws are oriented at an acute angle to the long axis of the shell, with their anterior ends pointing toward the dorsum. One of the jaws is folded into a U-shape, which probably approximates the shape of the jaw during life. Based on the measurements of the jaws and the shape of the shell, the jaws could not have touched the sides of the shell even if they were splayed out, implying that they could not have effectively served as opercula. Instead, in combination with the upper jaws and radula, they constituted the buccal apparatus that collected and conveyed food to the esophagus.",
    url = "https://doi.org/10.1515/agp-2017-0006",
    doi = "10.1515/agp-2017-0006",
    number = "1",
    pages = "109-120",
    volume = "67"
}

@article{doi101016jpalaeo201801038,
    author = "Slattery, Joshua and Harries, Peter J. and Sandness, Ashley L.",
    title = "Do marine faunas track lithofacies? Faunal dynamics in the Upper Cretaceous Pierre Shale, Western Interior, USA",
    year = "2018",
    journal = "Palaeogeography Palaeoclimatology Palaeoecology",
    url = "https://doi.org/10.1016/j.palaeo.2018.01.038",
    doi = "10.1016/j.palaeo.2018.01.038",
    openalex = "W2790907819",
    references = "doi1010029780470750711, doi10100797894009919727, doi101111j150239311971tb01864x, doi101126science2895478432, doi1011300091761319880160452ibolim23co2, doi101144gslsp19910580101, doi1023073545743, doi102475ajs3042105, doi103133pp393b, sohl1967upper"
}

Ammonites, as well as other fauna, were common in methane seeps of the Late Cretaceous Western Interior Seaway (WIS) of North America. Biogeochemical processes at the seeps, in particular the anaerobic oxidation of methane, produced a dissolved inorganic carbon reservoir with a low δ^13^C, manifested in the carbon isotope composition of the inorganic calcium carbonate concretions associated with the seeps and recorded in well-preserved shells of ammonites documented at the sites. Detailed sclerochronological sampling of six well-preserved specimens of *Baculites compressus* collected at seep sites in the Pierre Shale of South Dakota reveals three patterns that can be explained by reference to two specimens of the same species collected at age-equivalent non-seep sites. Three of the specimens exhibit uniformly low values of δ^13^C that are significantly different (unpaired t-test, p \<.0001) from similarly sized specimens of the same species collected at age-equivalent non-seep sites, suggesting that these ammonites lived at the seeps during the time interval over which the shell was secreted (adult portion of the shell). Two of the specimens collected from a seep site exhibit values of δ^13^C consistent with early ontogeny at a non-seep site followed by later ontogeny at a seep site. The values of δ^18^O of all the specimens reveal water temperatures of 16 to 28 °C. One small juvenile (15 mm long) collected at a seep site exhibits higher values of δ^13^C consistent with a non-seep environment, but values of δ^18^O that indicate very warm or slightly brackish water, suggesting that this animal lived in surface waters during its early ontogeny and died soon after arriving at the seep. Our results demonstrate that seep fluids affected the geochemistry of the water column above the seeps and that seeps provided habitats for ammonites in the WIS. Thus, although ammonites were mobile animals, they probably exploited a low-energy life style, remaining at the same site for extended periods of time.

@article{doi10247506201801,
    author = "Landman, Neil H. and Cochran, J. Kirk and Slovacek, Mariah and Larson, Neal L. and Garb, Matthew P. and Brezina, Jamie and Witts, James D.",
    title = "Isotope sclerochronology of ammonites (Baculites Compressus) from methane seep and non-seep sites in the Late Cretaceous Western Interior Seaway, USA: Implications for ammonite habitat and mode of life",
    year = "2018",
    journal = "American Journal of Science",
    abstract = "Ammonites, as well as other fauna, were common in methane seeps of the Late Cretaceous Western Interior Seaway (WIS) of North America. Biogeochemical processes at the seeps, in particular the anaerobic oxidation of methane, produced a dissolved inorganic carbon reservoir with a low δ^13^C, manifested in the carbon isotope composition of the inorganic calcium carbonate concretions associated with the seeps and recorded in well-preserved shells of ammonites documented at the sites. Detailed sclerochronological sampling of six well-preserved specimens of *Baculites compressus* collected at seep sites in the Pierre Shale of South Dakota reveals three patterns that can be explained by reference to two specimens of the same species collected at age-equivalent non-seep sites. Three of the specimens exhibit uniformly low values of δ^13^C that are significantly different (unpaired t-test, p \<.0001) from similarly sized specimens of the same species collected at age-equivalent non-seep sites, suggesting that these ammonites lived at the seeps during the time interval over which the shell was secreted (adult portion of the shell). Two of the specimens collected from a seep site exhibit values of δ^13^C consistent with early ontogeny at a non-seep site followed by later ontogeny at a seep site. The values of δ^18^O of all the specimens reveal water temperatures of 16 to 28 °C. One small juvenile (15 mm long) collected at a seep site exhibits higher values of δ^13^C consistent with a non-seep environment, but values of δ^18^O that indicate very warm or slightly brackish water, suggesting that this animal lived in surface waters during its early ontogeny and died soon after arriving at the seep. Our results demonstrate that seep fluids affected the geochemistry of the water column above the seeps and that seeps provided habitats for ammonites in the WIS. Thus, although ammonites were mobile animals, they probably exploited a low-energy life style, remaining at the same site for extended periods of time.",
    url = "https://doi.org/10.2475/06.2018.01",
    doi = "10.2475/06.2018.01",
    openalex = "W2886555074",
    references = "palamarczuk2011dinoflagellate"
}

Abstract Preferential dissolution of the biogenic carbonate polymorph aragonite promotes preservational bias in shelly marine faunas. While field studies have documented the impact of preferential aragonite dissolution on fossil molluscan diversity, its impact on regional and global biodiversity metrics is debated. Epicontinental seas are especially prone to conditions that both promote and inhibit preferential dissolution, which may result in spatially extensive zones with variable preservation. Here we present a multifaceted evaluation of aragonite dissolution within the Late Cretaceous Western Interior Seaway of North America. Occurrence data of mollusks from two time intervals (Cenomanian/Turonian boundary, early Campanian) are plotted on new high-resolution paleogeographies to assess aragonite preservation within the seaway. Fossil occurrences, diversity estimates, and sampling probabilities for calcitic and aragonitic fauna were compared in zones defined by depth and distance from the seaway margins. Apparent range sizes, which could be influenced by differential preservation potential of aragonite between separate localities, were also compared. Our results are consistent with exacerbated aragonite dissolution within specific depth zones for both time slices, with aragonitic bivalves additionally showing a statistically significant decrease in range size compared with calcitic fauna within carbonate-dominated Cenomanian–Turonian strata. However, we are unable to conclusively show that aragonite dissolution impacted diversity estimates. Therefore, while aragonite dissolution is likely to have affected the preservation of fauna in specific localities, time averaging and instantaneous preservation events preserve regional biodiversity. Our results suggest that the spatial expression of taphonomic biases should be an important consideration for paleontologists working on paleobiogeographic problems.

@article{doi101017pab201933,
    author = "Dean, Christopher D. and Allison, Peter A. and Hampson, Gary J. and Hill, Jon",
    title = "Aragonite bias exhibits systematic spatial variation in the Late Cretaceous Western Interior Seaway, North America",
    year = "2019",
    journal = "Paleobiology",
    abstract = "Abstract Preferential dissolution of the biogenic carbonate polymorph aragonite promotes preservational bias in shelly marine faunas. While field studies have documented the impact of preferential aragonite dissolution on fossil molluscan diversity, its impact on regional and global biodiversity metrics is debated. Epicontinental seas are especially prone to conditions that both promote and inhibit preferential dissolution, which may result in spatially extensive zones with variable preservation. Here we present a multifaceted evaluation of aragonite dissolution within the Late Cretaceous Western Interior Seaway of North America. Occurrence data of mollusks from two time intervals (Cenomanian/Turonian boundary, early Campanian) are plotted on new high-resolution paleogeographies to assess aragonite preservation within the seaway. Fossil occurrences, diversity estimates, and sampling probabilities for calcitic and aragonitic fauna were compared in zones defined by depth and distance from the seaway margins. Apparent range sizes, which could be influenced by differential preservation potential of aragonite between separate localities, were also compared. Our results are consistent with exacerbated aragonite dissolution within specific depth zones for both time slices, with aragonitic bivalves additionally showing a statistically significant decrease in range size compared with calcitic fauna within carbonate-dominated Cenomanian–Turonian strata. However, we are unable to conclusively show that aragonite dissolution impacted diversity estimates. Therefore, while aragonite dissolution is likely to have affected the preservation of fauna in specific localities, time averaging and instantaneous preservation events preserve regional biodiversity. Our results suggest that the spatial expression of taphonomic biases should be an important consideration for paleontologists working on paleobiogeographic problems.",
    url = "https://doi.org/10.1017/pab.2019.33",
    doi = "10.1017/pab.2019.33",
    openalex = "W2975316123",
    references = "doi1013063d93302016b111d78645000102c1865d, openalexw2468477906"
}

Two species of scaphitid ammonites (Ammonoidea: Ancyloceratina) from the Upper Cretaceous (lower Maastrichtian) of the Western Interior of North America are described. Hoploscaphites macer, n. sp., is medium size, with coarse ribs on the phragmocone, which become finer on the body chamber, and closely spaced ventrolateral tubercles. It occurs in the upper part of the Baculites baculus Zone and lower part of the overlying B. grandis Zone in the Pierre Shale in Montana, Wyoming, and Colorado, and in the Bearpaw Shale in Montana. Hoploscaphites criptonodosus (Riccardi, 1983) is larger and more coarsely ornamented, including one or two rows of lateral tubercles on the flanks of the phragmocone. It occurs in the upper part of the Baculites baculus Zone and overlying B. grandis Zone in the Pierre Shale in Montana, Wyoming, Colorado, and possibly South Dakota, and in the Bearpaw Shale in Montana and Saskatchewan, Canada. Both species form part of an evolving lineage of Hoploscaphites that first appears in the Western Interior of North America in the middle Campanian.

@article{doi1012060003009042711,
    author = "Landman, Neil H. and Kennedy, William J. and Larson, Neal L. and Grier, Joyce C. and Grier, James W. and Linn, Tom",
    title = "Description of Two Species of Hoploscaphites (Ammonoidea: Ancyloceratina) from the Upper Cretaceous (Lower Maastrichtian) of the U.S. Western Interior",
    year = "2019",
    journal = "Bulletin of the American Museum of Natural History",
    abstract = "Two species of scaphitid ammonites (Ammonoidea: Ancyloceratina) from the Upper Cretaceous (lower Maastrichtian) of the Western Interior of North America are described. Hoploscaphites macer, n. sp., is medium size, with coarse ribs on the phragmocone, which become finer on the body chamber, and closely spaced ventrolateral tubercles. It occurs in the upper part of the Baculites baculus Zone and lower part of the overlying B. grandis Zone in the Pierre Shale in Montana, Wyoming, and Colorado, and in the Bearpaw Shale in Montana. Hoploscaphites criptonodosus (Riccardi, 1983) is larger and more coarsely ornamented, including one or two rows of lateral tubercles on the flanks of the phragmocone. It occurs in the upper part of the Baculites baculus Zone and overlying B. grandis Zone in the Pierre Shale in Montana, Wyoming, Colorado, and possibly South Dakota, and in the Bearpaw Shale in Montana and Saskatchewan, Canada. Both species form part of an evolving lineage of Hoploscaphites that first appears in the Western Interior of North America in the middle Campanian.",
    url = "https://doi.org/10.1206/0003-0090.427.1.1",
    doi = "10.1206/0003-0090.427.1.1",
    openalex = "W2916151435",
    references = "doi101016jpalaeo201801038, doi1013060bda5c3f16bd11d78645000102c1865d, openalexw2343813256"
}

Abstract Members of the echinoid order Spatangoida, a highly diverse and abundant marine invertebrate clade, were important denizens of the Cretaceous Western Interior Seaway (WIS), an epicontinental seaway that divided North America in two during an interval of greenhouse conditions between roughly 100 and 65 million years ago. A phylogenetic analysis of spatangoids was conducted using a character matrix of 32 characters from 21 species. Species that occur in the WIS were considered comprehensively, and species from other regions such as South America, Europe, and North Africa were also incorporated into the analysis. Phylogenetic patterns retrieved are largely congruent with preexisting family-level classifications; however, species within several genera, especially Hemiaster and Heteraster, need to be reassigned so that classification better reflects phylogeny. The genera Washitaster and Heteraster are closely related, as are Mecaster, Palhemiaster, and Proraster; Pliotoxaster, Macraster, and Hemiaster; and Micraster and Diplodetus. Biogeographic patterns were also considered using the phylogeny, and several episodes of vicariance and range expansion were identified. These were possibly related to some of the various major episodes of sea-level rise and fall during the Cretaceous. In particular, Valangian–mid-Aptian regressions may have caused vicariance within Heteraster and Washitaster while other early spatangoid vicariance may be related to regressions during the late Aptian–early Cenomanian. Further, vicariance caused by regressions during the mid-Cenomanian–Maastrichtian may have driven diversification within Micraster and Diplodetus. Last, transgressions during the late Aptian–early Cenomanian seem to have spurred prominent range expansions in Mecaster and Hemiaster.

@article{doi101017jpa2020102,
    author = "Byrum, Steven and Lieberman, Bruce S.",
    title = "Phylogeny and biogeography of some Cretaceous spatangoid echinoids with special emphasis on taxa from the Western Interior Seaway",
    year = "2020",
    journal = "Journal of Paleontology",
    abstract = "Abstract Members of the echinoid order Spatangoida, a highly diverse and abundant marine invertebrate clade, were important denizens of the Cretaceous Western Interior Seaway (WIS), an epicontinental seaway that divided North America in two during an interval of greenhouse conditions between roughly 100 and 65 million years ago. A phylogenetic analysis of spatangoids was conducted using a character matrix of 32 characters from 21 species. Species that occur in the WIS were considered comprehensively, and species from other regions such as South America, Europe, and North Africa were also incorporated into the analysis. Phylogenetic patterns retrieved are largely congruent with preexisting family-level classifications; however, species within several genera, especially Hemiaster and Heteraster, need to be reassigned so that classification better reflects phylogeny. The genera Washitaster and Heteraster are closely related, as are Mecaster, Palhemiaster, and Proraster; Pliotoxaster, Macraster, and Hemiaster; and Micraster and Diplodetus. Biogeographic patterns were also considered using the phylogeny, and several episodes of vicariance and range expansion were identified. These were possibly related to some of the various major episodes of sea-level rise and fall during the Cretaceous. In particular, Valangian–mid-Aptian regressions may have caused vicariance within Heteraster and Washitaster while other early spatangoid vicariance may be related to regressions during the late Aptian–early Cenomanian. Further, vicariance caused by regressions during the mid-Cenomanian–Maastrichtian may have driven diversification within Micraster and Diplodetus. Last, transgressions during the late Aptian–early Cenomanian seem to have spurred prominent range expansions in Mecaster and Hemiaster.",
    url = "https://doi.org/10.1017/jpa.2020.102",
    doi = "10.1017/jpa.2020.102",
    openalex = "W3112581246",
    references = "arachchige2019taxonomy, doi101016002555648290027x, doi101016jgloplacha201312007, doi101017jpa201879, doi10108014772011003603556, doi101111j109600311994tb00179x, doi101144gslsp19880370119, doi101306m56578, doi1023073515270, doi105962bhltitle40014, openalexw3217097258, openalexw592572837"
}

Methane seeps were a common feature in the Late Cretaceous Western Interior Seaway of the United States. We document the occurrence of methane seep deposits in the Pierre Shale on the Cedar Creek Anticline in east-central Montana for the first time. The seep deposits occur in the lowermost part of the Baculites baculus Zone (the Endocostea typica Zone), corresponding to the lowermost Maastrichtian. They are therefore the youngest seeps yet described from the Western Interior Seaway. We conducted a detailed faunal analysis of a single seep deposit, together with geochemical investigation of both seep carbonates and molluscan shell material to determine palaeoenvironmental conditions. Oxygen isotope analysis of well-preserved molluscan shell material reveals water temperatures of between 19 and 27°C, while depleted carbon isotope values of seep carbonates are indicative of the anaerobic oxidation of methane. The morphology of the seep deposit suggests a strong advective flux of methane to the sediment–water interface. Comparison to a nearby contemporaneous non-seep site reveals that similar groups of organisms occur in both settings, albeit with varying relative abundances – the seep is numerically dominated by the lucinid bivalve Nymphalucina occidentalis. Substrate appears to be the major control on the diversity and palaeoecological composition of both seep and non-seep sites.

@article{doi101111let12396,
    author = "Ryan, Delaney R. and Witts, James D. and Landman, Neil H.",
    title = "Palaeoecological analysis of a methane seep deposit from the Upper Cretaceous (Maastrichtian) of the U.S. Western Interior",
    year = "2020",
    journal = "Lethaia",
    abstract = "Methane seeps were a common feature in the Late Cretaceous Western Interior Seaway of the United States. We document the occurrence of methane seep deposits in the Pierre Shale on the Cedar Creek Anticline in east-central Montana for the first time. The seep deposits occur in the lowermost part of the Baculites baculus Zone (the Endocostea typica Zone), corresponding to the lowermost Maastrichtian. They are therefore the youngest seeps yet described from the Western Interior Seaway. We conducted a detailed faunal analysis of a single seep deposit, together with geochemical investigation of both seep carbonates and molluscan shell material to determine palaeoenvironmental conditions. Oxygen isotope analysis of well-preserved molluscan shell material reveals water temperatures of between 19 and 27°C, while depleted carbon isotope values of seep carbonates are indicative of the anaerobic oxidation of methane. The morphology of the seep deposit suggests a strong advective flux of methane to the sediment–water interface. Comparison to a nearby contemporaneous non-seep site reveals that similar groups of organisms occur in both settings, albeit with varying relative abundances – the seep is numerically dominated by the lucinid bivalve Nymphalucina occidentalis. Substrate appears to be the major control on the diversity and palaeoecological composition of both seep and non-seep sites.",
    url = "https://doi.org/10.1111/let.12396",
    doi = "10.1111/let.12396",
    openalex = "W3081963456",
    references = "doi102110palo2019105"
}

@article{cui2021equivalent,
    author = "Cui, Jiangfeng and Si, Guangyao",
    title = "Equivalent anisotropic permeability of shale rocks: Effect of micro-fractures",
    year = "2021",
    journal = "Journal of Petroleum Science and Engineering",
    url = "https://doi.org/10.1016/j.petrol.2021.109085",
    doi = "10.1016/j.petrol.2021.109085",
    pages = "109085",
    volume = "207"
}

Abstract Methane seep deposits, comprising large, carbonate-rich mounds formed from hydrocarbon seepage, were widely distributed in the Late Cretaceous Western Interior Seaway (WIS) of North America. Well-preserved, methane-derived authigenic carbonates (MDACs) from these deposits have been shown to retain petrological, paleontological, and geochemical imprints of their ancient depositional setting, all of which are important for understanding the dynamics and evolution of the shallow, epeiric WIS. To better characterize the environmental conditions of WIS seeps, we applied clumped isotope paleothermometry to magnesium calcite MDAC samples from five seep localities in the upper Campanian Pierre Shale, South Dakota, USA. We measured 21 subsamples, including 18 micritic carbonates and demonstrated apparent clumped isotope equilibrium between MDACs and WIS bottom waters. Extreme 13C depletion in most samples (δ13C ranging to −45.44‰) indicates they were precipitated with oxidized methane as a major source of dissolved inorganic carbon, which itself implies a close association with ancient methanotrophic metabolism. The average clumped isotope paleotemperature from the micritic carbonates is 23 ± 7 °C (1σ standard deviation), which agrees with bottom water paleotemperatures inferred from δ18O measurements of MDACs and well-preserved mollusk shells at similar localities in the WIS. The calculated average δ18Ow value for these samples is −0.5 ± 1.7‰ (1σ SD), which is indistinguishable from previously reported calculation on Campanian seawater δ18Ow from fossil mollusk shells, but elevated above younger fossils collected from other locations in the WIS. Our conclusions are inconsistent with previously hypothesized disequilibrium for WIS MDAC clumped isotope and therefore we propose that fossil MDAC deposits may be used as paleotemperature archives.

@article{doi101130b358461,
    author = "Gao, Yang and Henkes, Gregory and Cochran, J. Kirk and Landman, Neil H.",
    title = "Temperatures of Late Cretaceous (Campanian) methane-derived authigenic carbonates from the Western Interior Seaway, South Dakota, USA, using clumped isotopes",
    year = "2021",
    journal = "Geological Society of America Bulletin",
    abstract = "Abstract Methane seep deposits, comprising large, carbonate-rich mounds formed from hydrocarbon seepage, were widely distributed in the Late Cretaceous Western Interior Seaway (WIS) of North America. Well-preserved, methane-derived authigenic carbonates (MDACs) from these deposits have been shown to retain petrological, paleontological, and geochemical imprints of their ancient depositional setting, all of which are important for understanding the dynamics and evolution of the shallow, epeiric WIS. To better characterize the environmental conditions of WIS seeps, we applied clumped isotope paleothermometry to magnesium calcite MDAC samples from five seep localities in the upper Campanian Pierre Shale, South Dakota, USA. We measured 21 subsamples, including 18 micritic carbonates and demonstrated apparent clumped isotope equilibrium between MDACs and WIS bottom waters. Extreme 13C depletion in most samples (δ13C ranging to −45.44‰) indicates they were precipitated with oxidized methane as a major source of dissolved inorganic carbon, which itself implies a close association with ancient methanotrophic metabolism. The average clumped isotope paleotemperature from the micritic carbonates is 23 ± 7 °C (1σ standard deviation), which agrees with bottom water paleotemperatures inferred from δ18O measurements of MDACs and well-preserved mollusk shells at similar localities in the WIS. The calculated average δ18Ow value for these samples is −0.5 ± 1.7‰ (1σ SD), which is indistinguishable from previously reported calculation on Campanian seawater δ18Ow from fossil mollusk shells, but elevated above younger fossils collected from other locations in the WIS. Our conclusions are inconsistent with previously hypothesized disequilibrium for WIS MDAC clumped isotope and therefore we propose that fossil MDAC deposits may be used as paleotemperature archives.",
    url = "https://doi.org/10.1130/b35846.1",
    doi = "10.1130/b35846.1",
    openalex = "W3138280633",
    references = "openalexw3198721165"
}

Abstract Methane seeps host rich biotic communities, forming patchy yet highly productive ecosystems across the global ocean. Persistent hydrocarbon emissions fuel chemosynthetic food webs at seeps. Methane seeps were abundant in the Western Interior Seaway of North America during the Late Cretaceous. This area also experienced intermittent ash falls, which negatively impacted the marine fauna. We propose that methane seeps acted as refugia during these environmental perturbations. We report a laterally continuous bentonite within the upper Campanian Baculites compressus Zone of the Pierre Shale in southwestern South Dakota (USA) that fortuitously cuts across a methane seep deposit. We compare the macroinvertebrate record below and above the bentonite at seep and non-seep sites. Our results reveal that the paleocommunity (measured by abundance and diversity) was largely unaffected by the ash fall at the seep site, whereas it was significantly altered at the non-seep site. Thus, methane seeps in the Western Interior Seaway may have provided refuges or served as oases in the aftermath of severe environmental perturbations.

@article{doi101130g493721,
    author = "Brophy, Shannon and Garb, Matthew P. and Naujokaitytė, Jonė and Witts, James D. and Landman, Neil H. and Cochran, J. Kirk and Brezina, Jamie",
    title = "Methane seeps as refugia during ash falls in the Late Cretaceous Western Interior Seaway of North America",
    year = "2021",
    journal = "Geology",
    abstract = "Abstract Methane seeps host rich biotic communities, forming patchy yet highly productive ecosystems across the global ocean. Persistent hydrocarbon emissions fuel chemosynthetic food webs at seeps. Methane seeps were abundant in the Western Interior Seaway of North America during the Late Cretaceous. This area also experienced intermittent ash falls, which negatively impacted the marine fauna. We propose that methane seeps acted as refugia during these environmental perturbations. We report a laterally continuous bentonite within the upper Campanian Baculites compressus Zone of the Pierre Shale in southwestern South Dakota (USA) that fortuitously cuts across a methane seep deposit. We compare the macroinvertebrate record below and above the bentonite at seep and non-seep sites. Our results reveal that the paleocommunity (measured by abundance and diversity) was largely unaffected by the ash fall at the seep site, whereas it was significantly altered at the non-seep site. Thus, methane seeps in the Western Interior Seaway may have provided refuges or served as oases in the aftermath of severe environmental perturbations.",
    url = "https://doi.org/10.1130/g49372.1",
    doi = "10.1130/g49372.1",
    openalex = "W4200558135",
    references = "doi102110palo2019105"
}

Abstract Improvements in analytical procedures in parallel with intercalibration of 40 Ar/ 39 Ar and U–Pb methods and laboratories, spurred since 2003 by the EarthTime geochronology community initiative, have led to ±2 σ uncertainties of the order of 50–100 ka, or better, for Cretaceous ash beds. Assembled here are 57 40 Ar/ 39 Ar ages and 17 238 U– 206 Pb ages of volcanic ash beds in strata of the Western Interior Basin of North America determined during the last 15 years since these improvements have been made. These age determinations span from 108 Ma in the middle Albian to 66 Ma in the latest Maastrichtian. Five of the 40 Ar/ 39 Ar ages from Campanian and Maastrichtian strata are newly reported here, whereas the remainder are from the literature. Building on the pioneering work of John Obradovich and Bill Cobban, where possible these age determinations are tied to ammonite and inoceramid biostratigraphy. For most ash beds, the temporal uncertainties, unlike earlier timescales for the Western Interior Basin, are much shorter than the duration of fossil biozones. Proposed ages for stage boundaries based on this review of the radioisotopic ages include: Maastrichtian–Danian, 66.02 ± 0.08 Ma; Campanian–Maastrichtian, 72.20 ± 0.20 Ma; Santonian–Campanian, 84.19 ± 0.38 Ma; Coniacian–Santonian, 86.49 ± 0.44 Ma; Turonian–Coniacian, 89.75 ± 0.38 Ma; Cenomanian–Turonian, 93.95 ± 0.05 Ma; Albian–Cenomanian, 100.00 ± 0.40 Ma. Six bentonites that occur within the Vascoceras diartianum, Neocardiocerus juddi, Prionocylus macombi, Scaphites preventricosus, Scaphites depressus and Desmoscaphites bassleri ammonite zones, dated using both 40 Ar/ 39 Ar and U–Pb methods, yield ages in agreement to within 150 ka and form the backbone of the Western Interior Basin timescale. In parallel, improvements in the taxonomy of ammonites, inoceramids and foraminifera, and recent field work, are better establishing the biostratigraphic framework for these age determinations. Each of these efforts contributes to the progressive refinement of the chronostratigraphic framework of the Western Interior Basin, and enhances its utility for global correlation.

@article{doi101144sp544202376,
    author = "Singer, Brad S. and Jicha, Brian R. and Sawyer, David A. and Walaszczyk, Ireneusz and Landman, Neil H. and Sageman, Bradley B. and McKinney, Kevin C.",
    title = "A 40 Ar/ 39 Ar and U–Pb timescale for the Cretaceous Western Interior Basin, North America",
    year = "2023",
    journal = "Geological Society London Special Publications",
    abstract = "Abstract Improvements in analytical procedures in parallel with intercalibration of 40 Ar/ 39 Ar and U–Pb methods and laboratories, spurred since 2003 by the EarthTime geochronology community initiative, have led to ±2 σ uncertainties of the order of 50–100 ka, or better, for Cretaceous ash beds. Assembled here are 57 40 Ar/ 39 Ar ages and 17 238 U– 206 Pb ages of volcanic ash beds in strata of the Western Interior Basin of North America determined during the last 15 years since these improvements have been made. These age determinations span from 108 Ma in the middle Albian to 66 Ma in the latest Maastrichtian. Five of the 40 Ar/ 39 Ar ages from Campanian and Maastrichtian strata are newly reported here, whereas the remainder are from the literature. Building on the pioneering work of John Obradovich and Bill Cobban, where possible these age determinations are tied to ammonite and inoceramid biostratigraphy. For most ash beds, the temporal uncertainties, unlike earlier timescales for the Western Interior Basin, are much shorter than the duration of fossil biozones. Proposed ages for stage boundaries based on this review of the radioisotopic ages include: Maastrichtian–Danian, 66.02 ± 0.08 Ma; Campanian–Maastrichtian, 72.20 ± 0.20 Ma; Santonian–Campanian, 84.19 ± 0.38 Ma; Coniacian–Santonian, 86.49 ± 0.44 Ma; Turonian–Coniacian, 89.75 ± 0.38 Ma; Cenomanian–Turonian, 93.95 ± 0.05 Ma; Albian–Cenomanian, 100.00 ± 0.40 Ma. Six bentonites that occur within the Vascoceras diartianum, Neocardiocerus juddi, Prionocylus macombi, Scaphites preventricosus, Scaphites depressus and Desmoscaphites bassleri ammonite zones, dated using both 40 Ar/ 39 Ar and U–Pb methods, yield ages in agreement to within 150 ka and form the backbone of the Western Interior Basin timescale. In parallel, improvements in the taxonomy of ammonites, inoceramids and foraminifera, and recent field work, are better establishing the biostratigraphic framework for these age determinations. Each of these efforts contributes to the progressive refinement of the chronostratigraphic framework of the Western Interior Basin, and enhances its utility for global correlation.",
    url = "https://doi.org/10.1144/sp544-2023-76",
    doi = "10.1144/sp544-2023-76",
    openalex = "W4388047374",
    references = "doi1013060bda5c3f16bd11d78645000102c1865d, openalexw2343813256"
}

Abstract Fossiliferous carbonate concretions are commonly found in sediments deposited in the Late Cretaceous Western Interior Seaway. Although concretions are diagenetic features, well-preserved fossils from within them have been instrumental in reconstructing the temperature and δ18O value of Western Interior Seaway seawater, which is essential for accurate reconstruction of Late Cretaceous climate. Here, we constrain formation conditions of Late Campanian and early Maastrichtian carbonate concretions by combining triple oxygen isotope measurements with carbonate clumped isotope paleothermometry on different carbonate phases within the concretions. We measured both fossil skeletal aragonite and sparry calcite infill from cracks and within macrofossil voids to evaluate differences between “primary” and “altered” geochemical signals. Based on the two temperature-sensitive isotope systems of the primary fossil shell aragonite, the temperature of the Western Interior Seaway was between 20 °C and 40 °C and was likely thermally stratified during the Campanian. The reconstructed δ18Oseawater values of ~−1‰ for Campanian Western Interior Seaway waters are similar to those expected for the open ocean during greenhouse climates, while the Maastrichtian Western Interior Seaway may have been more restricted, with a δ18Oseawater value of ~2‰, which reflects more evaporative conditions. We reconstructed the diagenetic history of the sparry infill and altered fossils using a fluid-rock mixing model. Alteration temperature, alteration fluid δ18O value, and the initial formation temperature were calculated by applying the fluid-rock mixing model to a particle swarm optimization algorithm. We found a different range of initial formation temperatures between the Campanian (25–38 °C) and Maastrichtian (9–28 °C). We also found that alteration in the presence of light meteoric fluids (δ18O ≈ −10‰) is required to explain both the sparry infill and the altered fossil isotopic values. Based on our results, both lithification and alteration of the carbonates occurred soon after burial, and light meteoric fluids support prior findings that high-topographic relief existed on the western margin of the Western Interior Seaway during the Late Cretaceous. As one of the first studies to apply these techniques in concert and across multiple mineralogical phases within samples, our results provide important constraints on paleoenvironmental conditions in an enigmatic ocean system and will improve interpretations of the overall health of ecosystems leading into the end-Cretaceous mass extinction.

@article{doi101130b375431,
    author = "Wostbrock, Jordan A.G. and Witts, James D. and Gao, Yang and Peshek, Catherine and Myers, Corinne and Henkes, Gregory and Sharp, Z. D.",
    title = "Reconstructing paleoenvironments of the Late Cretaceous Western Interior Seaway, USA, using paired triple oxygen and carbonate clumped isotope measurements",
    year = "2024",
    journal = "Geological Society of America Bulletin",
    abstract = "Abstract Fossiliferous carbonate concretions are commonly found in sediments deposited in the Late Cretaceous Western Interior Seaway. Although concretions are diagenetic features, well-preserved fossils from within them have been instrumental in reconstructing the temperature and δ18O value of Western Interior Seaway seawater, which is essential for accurate reconstruction of Late Cretaceous climate. Here, we constrain formation conditions of Late Campanian and early Maastrichtian carbonate concretions by combining triple oxygen isotope measurements with carbonate clumped isotope paleothermometry on different carbonate phases within the concretions. We measured both fossil skeletal aragonite and sparry calcite infill from cracks and within macrofossil voids to evaluate differences between “primary” and “altered” geochemical signals. Based on the two temperature-sensitive isotope systems of the primary fossil shell aragonite, the temperature of the Western Interior Seaway was between 20 °C and 40 °C and was likely thermally stratified during the Campanian. The reconstructed δ18Oseawater values of \textasciitilde −1‰ for Campanian Western Interior Seaway waters are similar to those expected for the open ocean during greenhouse climates, while the Maastrichtian Western Interior Seaway may have been more restricted, with a δ18Oseawater value of \textasciitilde 2‰, which reflects more evaporative conditions. We reconstructed the diagenetic history of the sparry infill and altered fossils using a fluid-rock mixing model. Alteration temperature, alteration fluid δ18O value, and the initial formation temperature were calculated by applying the fluid-rock mixing model to a particle swarm optimization algorithm. We found a different range of initial formation temperatures between the Campanian (25–38 °C) and Maastrichtian (9–28 °C). We also found that alteration in the presence of light meteoric fluids (δ18O ≈ −10‰) is required to explain both the sparry infill and the altered fossil isotopic values. Based on our results, both lithification and alteration of the carbonates occurred soon after burial, and light meteoric fluids support prior findings that high-topographic relief existed on the western margin of the Western Interior Seaway during the Late Cretaceous. As one of the first studies to apply these techniques in concert and across multiple mineralogical phases within samples, our results provide important constraints on paleoenvironmental conditions in an enigmatic ocean system and will improve interpretations of the overall health of ecosystems leading into the end-Cretaceous mass extinction.",
    url = "https://doi.org/10.1130/b37543.1",
    doi = "10.1130/b37543.1",
    openalex = "W4400580541",
    references = "doi101016jpalaeo201801038, doi102110palo2019105"
}

@article{anderson2025paleobiogeographic,
    author = "Anderson, A.J. F. and Schafer, Thomas C.",
    title = "Paleobiogeographic Range Maps of Select Baculites Species of the Late Campanian Western Interior Seaway",
    year = "2025",
    journal = "Transactions of the Kansas Academy of Science",
    url = "https://doi.org/10.1660/062.128.0108",
    doi = "10.1660/062.128.0108",
    number = "1-2",
    openalex = "W4410749508",
    volume = "128",
    references = "doi101007978940179633010, doi101016jpalaeo200405013, doi101016jpalaeo200411016, doi101016jpalaeo200804014, doi101017jpa2020102, doi101017s0022336000020011, doi101029jc082i027p03861, doi101098rspb20101617, doi1023073514731, doi107717peerj6910"
}

Percussion drilling technology can be used to increase the rate of penetration in deep shale reservoirs, but the interaction mechanism among impact loads, drilling teeth and rock has not been sufficiently investigated. For this reason, shales with different bedding angles are used to carry out impact compression and tensile experiments as well as the rock-breaking experiments by single axe-shaped tooth, the variation of dynamic strengths, rock failure characteristics, fractal dimensions, and tensile/compression ratios under different load-bedding angles (α) are investigated. Then, the three-dimensional scanning device is used to measure the penetration depth and rock-breaking volume under different load-bedding angles. The results show that with the increase of load-bedding angle (0°–90°), the compressive strength decreases and then increases, with the lowest strength at α = 45° and the highest strength at α = 0°; the tensile strength decreases and then increases, with the lowest strength near α = 30° and the highest strength at α = 90°. With the growing impact rate, the effect of load-bedding angle on dynamic compressive strength decreases, and the effect on dynamic tensile strength becomes more significant. When the impact velocity is high (≥8.0 m/s), the tensile-compressive ratio first decreases and then increases, and both reach a minimum at a load-bedding angle of 30° and a maximum at 60°. With the increasing of the load-bedding angle, the depth of tooth penetration increases and then decreases, and the highest depth of tooth penetration and the highest energy absorption efficiency are achieved at α = 45°; the width of the impact pit increases and then decreases, and the maximum width value is achieved at α = 30°, with the smallest value of the specific work value of the rock-breaking. The results have significant reference value for improving the rock-breaking efficiency of percussion drilling in deep anisotropic formations.

@article{doi101016jpetsci202503036,
    author = "Xi, Yan and Yao, Yu and Zhao, Haifeng and Li, Qian and Li, Jun and Chen, Yingchun",
    title = "Dynamic characteristics of anisotropic shale and rock-breaking efficiency of the axe-shaped tooth under different impact load-bedding angles",
    year = "2025",
    journal = "Petroleum Science",
    abstract = "Percussion drilling technology can be used to increase the rate of penetration in deep shale reservoirs, but the interaction mechanism among impact loads, drilling teeth and rock has not been sufficiently investigated. For this reason, shales with different bedding angles are used to carry out impact compression and tensile experiments as well as the rock-breaking experiments by single axe-shaped tooth, the variation of dynamic strengths, rock failure characteristics, fractal dimensions, and tensile/compression ratios under different load-bedding angles (α) are investigated. Then, the three-dimensional scanning device is used to measure the penetration depth and rock-breaking volume under different load-bedding angles. The results show that with the increase of load-bedding angle (0°–90°), the compressive strength decreases and then increases, with the lowest strength at α = 45° and the highest strength at α = 0°; the tensile strength decreases and then increases, with the lowest strength near α = 30° and the highest strength at α = 90°. With the growing impact rate, the effect of load-bedding angle on dynamic compressive strength decreases, and the effect on dynamic tensile strength becomes more significant. When the impact velocity is high (≥8.0 m/s), the tensile-compressive ratio first decreases and then increases, and both reach a minimum at a load-bedding angle of 30° and a maximum at 60°. With the increasing of the load-bedding angle, the depth of tooth penetration increases and then decreases, and the highest depth of tooth penetration and the highest energy absorption efficiency are achieved at α = 45°; the width of the impact pit increases and then decreases, and the maximum width value is achieved at α = 30°, with the smallest value of the specific work value of the rock-breaking. The results have significant reference value for improving the rock-breaking efficiency of percussion drilling in deep anisotropic formations.",
    url = "https://doi.org/10.1016/j.petsci.2025.03.036",
    doi = "10.1016/j.petsci.2025.03.036",
    openalex = "W4408888082",
    references = "cui2021equivalent"
}

@incollection{kaiser2026performance,
    author = "Kaiser, P.K. and Mackay, C. and Morgenstern, N.R.",
    title = "Performance of a Shaft in Weak Rock (Bearpaw Shale)",
    year = "2026",
    booktitle = "Rock Mechanics - Volume 2",
    url = "https://doi.org/10.1201/9781003762911-12",
    doi = "10.1201/9781003762911-12",
    pages = "613-622"
}