Nature of thrusting along western flank of Bighorn Mountains, Wyoming
The northern portion of the Bighorn Mountains is characterized by opposed mountain-front thrusts, of which the southwest direction is dominant. Blind basement thrusts along the northeastern flank do not pierce the folded Paleozoic cover; whereas on the western flank, southwest-directed thrust segments expose Precambrian rocks along a 24-km (14-mi) extent. Field studies on the western flank show evidence of four major southwest-directed thrust segments delineated by tear-fault boundaries, which include from northwest to southeast: (1) the Five Springs thrust, a low-angle, out-of-the-syncline fault mainly involving the sedimentary sequence; (2) the Bear Creek thrust, a continuation of the Five Springs out-of-the-syncline fault; (3) the South Beaver Creek thrust, which juxtaposes Precambrian rocks against a tectonically thinned, overturned anticlinal limb of Mississippian through Jurassic rocks and which is inward from an out-of-the-syncline thrust involving little displacement of Jurassic formations; and (4) a mountain-front reentrant that coincides with the zone where the South Beaver Creek thrust continues beneath Paleozoic cover, causing the upper flexure of a double monocline. The central portion of the Bighorn Mountains is thrust eastward, whereas the northern portion is thrust southwestward with much less displacement. The segmented association of southwest-directed basement thrusts along the western flank of the northern Bighorns is indicative of the major transport direction for that portion of the Bighorn uplift.
- Research Organization:
- Iowa State Univ., Ames
- OSTI ID:
- 7042085
- Report Number(s):
- CONF-8609129-
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Vol. 70:8; ISSN AAPGB
- Country of Publication:
- United States
- Language:
- English
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