West-east stratigraphic transect of Cretaceous rocks - Southwestern Montana to western Minnesota
- Geological Survey, Denver, CO (United States)
- North Dakota Geological Survey, Bismark (United States)
- South Dakota School of Mines, Rapid City (United States)
- South Dakota Geological Survey, Vermillion (United States)
- Minnesota Geological Survey, St. Paul (United States)
- St. Cloud State Univ., MN (United States)
In Montana, North and South Dakota, and Minnesota, Cretaceous strata of the Western Interior foreland basin are preserved today in Laramide structural and cratonic basins. The Western Interior basin was asymmetric: more than 17,000 ft of strata are present in southwestern Montana, less than 1,000 ft in eastern South Dakota. Asymmetry resulted from varying rates of subsidence due to tectonic and sediment loading. Cretaceous rocks consist primarily of sandstone, siltstone, claystone, and shale. Conglomerate is abundant along the western margin, whereas limestone is generally restricted to the eastern shelf. A west-east transect of the Cretaceous system from southwestern to east-central Montana, the Black Hills and Williston basin, and eastern South Dakota and western Minnesota includes regional facies relations, sequence boundaries, and biostratigraphic and radiometric correlation. These strata include more than 10,000 ft of synorogenic conglomerate facies of the Late Cretaceous Beaverhead Group. Cretaceous strata in east-central Montana (about 4,500 ft thick) lie at the approximate depositional axis of the basin and are mostly marine terrigenous rocks. Chert-pebble units in these rocks reflect unconformities to the west. The Cretaceous system in North and South Dakota (1,500 - 2,000 ft thick) represents a marine shelf sequence dominated by shale and limestone overlain by coastal sandstone and nonmarine rocks. Major sequence boundaries are at the base of the Lakota Formation, Fall River Sandstone, and Muddy Sandstone, and bracket the Niobrara Formation.
- OSTI ID:
- 6130115
- 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
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58 GEOSCIENCES
MINNESOTA
SEDIMENTARY BASINS
MONTANA
NORTH DAKOTA
STRATIGRAPHY
SOUTH DAKOTA
WILLISTON BASIN
OIL FIELDS
PETROLEUM GEOLOGY
CRETACEOUS PERIOD
GEOLOGIC HISTORY
DEVELOPED COUNTRIES
FEDERAL REGION V
FEDERAL REGION VIII
GEOLOGIC AGES
GEOLOGIC DEPOSITS
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