Structural relationship of the Beartooth Mountains and Big Horn basin in south-central Montana and northwestern Wyoming

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

OSTI ID:6093323

Clark, D M ^[1]

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1. Exodus-Exploration Inc., Billings, MT (United States)

Geologic structure along the Beartooth Mountain front and adjacent Big Horn basin in south-central Montana and northwestern Wyoming has been the subject of considerable debate for many years. Directional drilling by Amoco Production Company, located on the northeast corner of the Beartooth block, indicates three things. (1) Western Big Horn basin Paleozoic and Mesozoic sections recumbently folded 2 mi (3.2 km) under the northeast corner of the Beartooth block, measured horizontally from the surface exposure of the Beartooth fault. (2) The main Beartooth fault dips 19{degrees} northwest at a depth of 8,300 to 8,400 ft (2,530 to 2,560 km), 1 mi (1.6 km) from the surface exposure of the main Beartooth fault. (3) The main Beartooth fault appears to be a component of a complex fault system which horizontally displaces and faults-out formations in both the Paleozoic and Mesozoic section on the upper limb of the recumbent fold. In addition to the drilling data, interior Beartooth Mountain faults, with dominant northeast and east-west structural orientation, show reactivation of left-lateral movement, intersecting the Beartooth front and offsetting Paleozoic and Mesozoic sections 1-2 mi (1.6-3.2 km) horizontally. Reactivation of some of these faults seems to coincide with the intrusion of Tertiary (Eocene ) igneous bodies along some of the same structural trends. Beartooth front fold orientation and fault movement correlated with a reexamination of internal block fault systems lend additional weight to the argument of horizontal compression as a major factor in late Laramide formation of geologic structure along the northeast face of the Beartooth Mountains.

• OSTI ID: 6093323
• 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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