Mississippian and Pennsylvanian (Carboniferous) systems in the US - Montana

Journal Article · Mon Jan 01 04:00:00 EST 1979 · U.S. Geol. Surv., Prof. Pap.; (United States)

OSTI ID:5754992

Smith, D L; Gilmour, E H

Carboniferous strata underlie all but the northwestern corner of Montana and are well-exposed on the flanks of tertiary uplifts throughout the state. The Carboniferous rock package attains a maximum thickness of 1000 M along the Big Snowy Trough, an east-trending paleostructural feature in central Montana; it thins to 300 M and 450 M in N. and S. Montana, respectively, on the flanks of the trough. The contact of the Carboniferous rocks with underlying strata is unconformable, the rocks beneath the unconformity ranging in age from Ordovician to latest Devonian and generally increasing in age toward the southern part of the state. The contact of Carboniferous strata with overlying rocks also is unconformable, the overlying strata ranging from Permian and Triassic at the Montana-Wyoming border to middle Jurassic in the northern part of the state. Carboniferous rocks of Montana are divided into 4 lithologic units, each deposited under a different set of tectonic and environmental conditions. These units are the Madison group, the Big Snowy group, the Amsden group, and the Quadrant formation. 89 references.

• OSTI ID: 5754992
• Journal Information: U.S. Geol. Surv., Prof. Pap.; (United States), Journal Name: U.S. Geol. Surv., Prof. Pap.; (United States) Vol. 1110-X; ISSN XGPPA
• Country of Publication: United States
• Language: English

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