Upper Cretaceous and lower Tertiary rocks of the Bighorn Basin, Wyoming: a new look at the basin's stratigraphy and tectonic history
Upper Cretaceous and lower Tertiary rocks of the Bighorn Basin consist of a sequence of intertonguing marine and continental rocks of the Mesaverde Formation (Campanian in age) overlain by a thick sequence of continental rocks that includes the Maastrichtian Meeteetse and Lance Formations and the Paleocene Fort Union Formation. A subsurface study using geophysical logs from boreholes that penetrated these formations has shown that: 1) the Mesaverde exhibits significant changes in thickness within the basin that can be related to both activation of basin-bounding faults during initial Laramide tectonic movements and to regional interformational unconformities; 2) a laterally discontinuous shale unit in the uppermost Lance Formation of the western Bighorn Basin may be correlative with a marine unit of the Harebell Formation in the Jackson Hole area to the west or may be a lacustrine unit that formed in the deep subsiding trough of the Bighorn Basin during Lance deposition; and 3) a regional eastward thinning of about 1000 feet exists in the Lance Formation across the basin. These observations indicate that: 1) Laramide tectonic activity may have begun in middle Campanian time; 2) a reentrant of the Cretaceous Seaway (or a large lake) existed in the western part of the basin until latest Maastrichtian time; and 3) the lower Fort Union in parts of the Bighorn Basin may be a facies of the latest Cretaceous Lance Formation or, a basin-wide unconformity at the base of the Fort Union may exist as a result of major Laramide tectonic activity.
- Research Organization:
- Univ. of Wyoming, Laramie (USA)
- OSTI ID:
- 6462009
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Vol. 17; ISSN GAAPB
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
580100 -- Geology & Hydrology-- (-1989)
580201* -- Geophysics-- Seismology & Tectonics-- (1980-1989)
CENOZOIC ERA
CRETACEOUS PERIOD
FEDERAL REGION VIII
GEOLOGIC AGES
GEOLOGIC FAULTS
GEOLOGIC FORMATIONS
GEOLOGIC FRACTURES
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
GEOLOGY
MESOZOIC ERA
NORTH AMERICA
SEDIMENTARY BASINS
STRATIGRAPHY
TECTONICS
TERTIARY PERIOD
USA
WYOMING