Stratigraphic and structural relations of Lower Triassic rocks within the frontal fold-and-thrust zone of southwestern Montana

Conference · Sat Jun 01 00:00:00 EDT 1991 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:5874670

Paull, R K; Paull, R A ^[1]

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1. Univ. of Wisconsin, Milwaukee (United States)

New sections of Lower Triassic rocks were measured within the frontal fold-and-thrust zone of southwestern Montana at Garfield Canyon, Horse Prairie Creek, Kennison Spring, and Birch Creek to clarify stratigraphic and structural relations. Triassic rocks disconformably overlie Upper Permian units and unconformably underlie younger rocks. From oldest to youngest, they include the Dinwoody, Woodside, and Thaynes formations. The Dinwoody consists of shale, siltstone, and limestone; thickness varies from 152 to 273 m. Red beds of the Woodside thin northward to zero in the northern Tendoy Mountains. The Thaynes is comprised of limestone, siltstone, and sandstone; thickness varies from 244 m in the south, zero in the central area, to 51 m in the north. North of the Woodside termination, recognition of the Thaynes depends upon recovery of Smithian conodonts. Conodonts provide correlation and biofacies information for this study. From Birch Creek northward, conodonts are basinal, consistent with lithofacies data. This area is within the McCartney Mountain salient, a depositional basin which may have existed on the craton margin prior to thrusting. However, there is no evidence to support basinal conditions in the Blacktail Mountain salient to the south. Although thermal alteration values for most conodonts are within the range of oil and condensate production, those from Birch Creek north exceed the stability regime for hydrocarbons.

• OSTI ID: 5874670
• Report Number(s): CONF-9107109-; CODEN: AABUD
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 75:6; Conference: American Association of Petroleum Geologists (AAPG) Rocky Mountain Section meeting, Billings, MT (United States), 28-31 Jul 1991; ISSN 0149-1423
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
58 GEOSCIENCES
MONTANA
SEDIMENTARY BASINS
GEOLOGIC FAULTS
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STRATIGRAPHY
BIOLOGICAL MARKERS
FOSSILS
GEOLOGIC FORMATIONS
LITHOLOGY
SOURCE ROCKS
TRIASSIC PERIOD
WESTERN US OVERTHRUST BELT
DEVELOPED COUNTRIES
FEDERAL REGION VIII
GEOLOGIC AGES
GEOLOGIC FRACTURES
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020200* - Petroleum- Reserves
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580000 - Geosciences