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carbon
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Cenozoic
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Quaternary (1)
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Tertiary
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Hanna Formation (1)
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Chordata
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Vertebrata
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Reptilia
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Diapsida
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Archosauria
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dinosaurs
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Theropoda
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Carnosauria
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Pterosauria
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Ichthyosauria (2)
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Lepidosauria
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Squamata
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Lacertilia
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Sauropterygia
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Cephalopoda
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isotopes
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stable isotopes
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Mesozoic
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Albian
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upper Albian (2)
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Aptian (1)
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Bear River Formation (3)
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Blackleaf Formation (1)
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Burro Canyon Formation (1)
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Clearwater Formation (1)
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Cloverly Formation (4)
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Inyan Kara Group (1)
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Mowry Shale (10)
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Muddy Sandstone (5)
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Skull Creek Shale (1)
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Middle Cretaceous (2)
-
Upper Cretaceous
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Bearpaw Formation (1)
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Campanian (2)
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Cenomanian (4)
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Cody Shale (2)
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Coniacian (1)
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Fort Hays Limestone Member (1)
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Frontier Formation (10)
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Lance Formation (2)
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Mesaverde Group (2)
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Niobrara Formation (1)
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Pierre Shale (1)
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Santonian (2)
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Senonian (1)
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Smoky Hill Chalk Member (1)
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Turonian (3)
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Viking Formation (7)
-
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Jurassic
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Lower Jurassic
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Toarcian (2)
-
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Middle Jurassic (2)
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Oxford Clay (1)
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Twin Creek Limestone (1)
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Upper Jurassic
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Morrison Formation (5)
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Oxfordian (1)
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Stump Formation (2)
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Sundance Formation (7)
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Swift Formation (1)
-
-
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lower Mesozoic (1)
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Nugget Sandstone (2)
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Triassic
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Lower Triassic
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Dinwoody Formation (1)
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metal ores
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metals
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lead
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Bighorn Mountains (4)
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Rocky Mountains foreland (4)
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Paleozoic
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Carboniferous
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Devonian (1)
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Ordovician
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Upper Ordovician
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Ashgillian (1)
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Permian
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Phosphoria Formation (1)
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Upper Permian (1)
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Tensleep Sandstone (2)
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upper Paleozoic (1)
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petroleum
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petrology (3)
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upper Precambrian
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Thermopolis Shale
Storm-influenced shelf deposition of the lower sandstone member, Lower Cretaceous Thermopolis Shale, southwestern Montana
Stratigraphy of Non-Marine Upper Jurassic and Lower Cretaceous Rocks, Southern Big Horn Mountains, Wyoming
—Isopach map of Thermopolis Shale showing distribution of Muddy Sandstone a...
Geochronology of late Albian−Cenomanian strata in the U.S. Western Interior
Jurassic-Cretaceous Nonmarine Foreland Basin Sedimentation in Western United States: ABSTRACT
Stratigraphy and Petroleum Potential of Lower Cretaceous Inyan Kara Group in Northeastern Wyoming, Southeastern Montana, and Western South Dakota
MORRISON, CLOVERLY, AND SYKES MOUNTAIN FORMATIONS, NORTHERN BIGHORN BASIN, WYOMING AND MONTANA
Source Rock Potential of Middle Cretaceous Rocks in Southwestern Montana
Big Piney-La Barge Producing Complex, Wyoming
Palaeoecology of the marine reptiles of the Redwater Shale Member of the Sundance Formation (Jurassic) of central Wyoming, USA
Lower Cretaceous of Wyoming and Southern Rockies: ABSTRACT
Ekalakia (Decapoda: Brachyura): The Preservation of Eyes Links Cretaceous Crabs to Jurassic Ancestors
Abstract An important transgressive-regressive-transgressive sequence is recorded in the Albian strata of the Western Interior Cretaceous basin. A widespread marine shale, mapped throughout the basin, is known in different areas as the Skull Creek, Kiowa, Thermopolis, and Joli Fou (Canada) shales (Figs. 2.5 and 6.1). Equivalent strata in western Wyoming in the basin-margin area are generally included in the Dakota Group or Bear River formation. The shale deposits, which accumulated during a high stand of the Albian Sea, are correlated over large areas, either by contained faunas or by stratal continuity. The shales, generally 100 to 200 ft thick, represent the first widespread transgression of the Cretaceous sea into the United States portion of the Western Interior basin. Overlying regressive sandstone units, named the Muddy, J, or Viking (Canada) sandstones, are widespread and productive of petroleum in stratigraphic or structural traps. Generally less than 100 ft thick, these sandstones were deposited in a range of environments from freshwater to marine. They are generally regarded as deposits related to a lowering and rising of sea level. The following transgression is recorded by the widespread marine Mowry Formation and other highstand deposits. When the history of these strata is related to radiometric dates from associated bentonite beds, the sequence spans the time interval of approximately 96 to 98 m.y.b.p. The major event correlates with the worldwide sea-level drop 97 m.y.b.p., reported by Vail, Mitchum, and Thompson (1977) and Hancock, (1975).
Stratigraphy and Conditions Governing Petroleum Occurrence in Lower Cretaceous Rocks, Rocky Mountain Region: ABSTRACT
Stratigraphy and Petroleum Potential of Dakota Group (Cretaceous), Western Denver Basin, Colorado
Cretaceous tintinnids from the western interior of the United States
S uites of bentonite beds in the Mowry Formation and in the lower part of the Frontier Formation in a 40,000-square-mile area of north-central Wyoming were sampled and described at measured sections in the interval between the Muddy Sandstone and the sandstone in the lower part of the Frontier Formation. After binocular examination, more than 800 samples were studied by X-ray and microscopic methods. The sand fraction yields a typical igneous mineral assemblage. Montmorillonite, the chief constituent of bentonites, is relatively uniform except for significant differences in the exchangeable cations. The chemical composition of the montmorillonite seems to be related to the amounts of the various types of feldspars. By combining mineralogical composition with subsurface data from electric logs, the bentonites can be correlated broadly. Most of the beds consist of coalescing lobate forms as shown by isopach maps. Based on areal correlation and lithologic descriptions of the bentonites, the stratigraphic relationships of the Mowry Formation become evident. Bentonites have the same physical origin as recent wind-transported volcanic-ash beds. Mineralogy, textures, and distributions of the Wyoming bentonites are also similar to recently deposited ash beds. The gross and a few detailed features of bentonites and ash beds can be explained by a qualitative physical model. The important factors which determine the physical properties of the ash beds are intensity of volcanic explosion, amounts of gaseous and solid materials, particle-size range of the solid materials, and the high-altitude winds (above 40,000 feet) which transport the ash to depositional sites. The igneous source-rock type of the bentonites may be determined fairly accurately from analyses of the sand-sized fraction. Analyses of the Wyoming bentonites suggest source-rock variations from rhyolite to andesite, although dacite, latite, and quartz latite are the common types. Geological evidence indicates that the vitric ashes of the Wyoming bentonites altered after deposition probably by hydrolysis. The process may be expressed as a series of acid-base reactions. The minerals formed by alteration indicate alkaline conditions, but the high magnesium content does not preclude a neutral to slightly acid environment. The stratigraphy of the bentonites suggests an intimate relationship to the sedimentational and tectonic history of the Cretaceous beds. Major bentonites invariably occur in the same cyclical sequence—ideally, from bottom to top, shale, coal, bentonite, shale grading to sandstone or conglomerate. If the bentonites are used as time lines, a tectonic interpretation of sedimentational patterns is possible. The history is as follows: (1) high basin, (2) volcanic activity (to the west), (3) uplift in the source and coincident subsidence in the basin, (4) continuation and intensification of (3), and (5) stand-still or abrupt uplift in basin with cessation of uplift in the source. We propose three major orogenic pulses in the Cretaceous as represented by Thermopolis-Mowry-Frontier, Cody-Mesaverde, Lewis (and Meteetse)-Lance Formations. Minor orogenic pulses represented by intraformational cycles are superimposed on the major events.