Biofacies expression of Upper Cretaceous sequences in the Rock Springs uplift
- Exxon Production Research Co., Houston, TX (United States)
The sequence-stratigraphic framework and vertical succession of depositional environments in the Upper Cretaceous section of the Rock Springs uplift is expressed in the biofacies patterns as well as in the stratal stacking patterns. Vertical trends in six biofacies parameters track affinities to marine and nonmarine environments as well as proximity to the paleoshoreline. These six parameters and their environmental significance include the relative proportion of herbaceous kerogen (land-derived), amorphous kerogen (marine), dinoflagellates (marine), bisaccate pollen (land-derived but buoyant and easily transported offshore), and the abundance and diversity of benthic foraminifera (both increase offshore). Shoaling marine environments are characterized by an increasing proportion of herbaceous kerogen and decreasing proportions of amorphous kerogen, dinoflagellated, bisaccates, and the abundance and diversity of benthic foraminifera. Conversely, a deepening-upward marine sedimentary succession is characterized by an opposite trend in these parameters. A synthesis of the six biofacies parameters emphasizes the third-order cyclicity of the stratal succession as reflected in the well-developed third-order downlap surfaces and condensed sections. The biofacies trends indicate the transgressive nature of the lower Rock Springs and lower Lewis formations, and the progradational nature of the upper arts of the Baxter, Blair, and Rock Springs formations. An overall progradational (i.e., shoaling) character is exhibited in the three lower sequences (Baxter through Rock Springs) by the progressively decreasing abundance of amorphous kerogen, dinoflagellates, and foraminifera.
- OSTI ID:
- 5874647
- Report Number(s):
- CONF-910403-; CODEN: AABUD
- Journal Information:
- AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 75:3; Conference: Annual meeting of the American Association of Petroleum Geologists (AAPG), Dallas, TX (United States), 7-10 Apr 1991; ISSN 0149-1423
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
58 GEOSCIENCES
PETROLEUM DEPOSITS
SOURCE ROCKS
PALYNOLOGY
STRATIGRAPHY
WYOMING
CRETACEOUS PERIOD
DEPOSITION
DINOFLAGELLATE
FORAMINIFERA
GEOLOGIC HISTORY
GEOLOGIC MODELS
KEROGEN
PALEONTOLOGY
POLLEN
ANIMALS
BITUMINOUS MATERIALS
CARBONACEOUS MATERIALS
DEVELOPED COUNTRIES
FEDERAL REGION VIII
GAMETES
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGY
GERM CELLS
INVERTEBRATES
MASTIGOPHORA
MATERIALS
MATTER
MESOZOIC ERA
MICROORGANISMS
MINERAL RESOURCES
NORTH AMERICA
ORGANIC MATTER
PROTOZOA
RESOURCES
SARCODINA
USA
020200* - Petroleum- Reserves
Geology
& Exploration
580000 - Geosciences