Sedimentary regime of Tullock Member of Fort Union Formation, Tullock Creek type locality, South-central Montana

Conference · Fri Aug 01 04:00:00 EDT 1986 · Am. Assoc. Pet. Geol., Bull.; (United States)

OSTI ID:6962818

Brown, J L

The early Paleocene Tullock Member of the Fort Union Formation at its type locality was deposited in a low-gradient riverine system. This interpretation is based on studies of sedimentary structures, geometry, thickness trends, and sand-percent isopach maps. Lithologies consist of interbedded sandstones, siltstones, shales, and thin coal beds. Sandstones 10 m (32.8 ft) thick contain fining-upward, fine-grained, structureless units with erosional bases capped by climbing-ripple lamination. Some sandstones have claystone rip-up clasts at their bases. The sandstones are discrete, highly convex bodies with symmetrical cross sections and flat erosional bases. These sandstone bodies are isolated show no stacking or coalescing, and are concentration in the middle of the Tullock Member. Interbedded calcareous siltstones show ripple cross-laminae and contain elongate calcareous nodules 4 to 16 cm (1.6 to 6.3 in.) long, oriented parallel to the bedding plane. They also contain well-preserved, fragmented leaf impressions. Carbonaceous shale predominates in the upper and lower third of the member. These shales show very thin lamination, contain abundant plant fragments, and have a mottled rooted texture. Thin, discontinuous coal beds are found within the lower third of the Tullock.

• Research Organization: Geological Survey, Denver, CO
• OSTI ID: 6962818
• Conference Information: Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Journal Volume: 70:8
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
011000 -- Coal
Lignite
& Peat-- Reserves
Geology
& Exploration
02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
CENOZOIC ERA
COAL DEPOSITS
FEDERAL REGION VIII
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC FORMATIONS
GEOLOGY
MINERAL RESOURCES
MONTANA
NORTH AMERICA
RESERVOIR ROCK
RESOURCES
ROCKS
SANDSTONES
SEDIMENTARY ROCKS
SHALES
SILTSTONES
TERTIARY PERIOD
USA