Single-stage, northeast-directed thrusting on the Laramide Beartooth fault.

摘要

This study focuses on the synkinematic sediments along the Beartooth thrust fault in order to assess both the Laramide paleostress history of the Beartooth uplift, and how far the Bighorn Basin's syn-orogenic deposits have been overridden. The sediments shed into the basin by the ascending Beartooth block were folded and overridden by the Beartooth thrust. In the vicinity of Red Lodge, MT, the Paleocene/Eocene sediments were overthrust 4-7 km, based on truncated alluvial fans. These sediments contain a population of two orthogonal systematic joint sets. The older of the two strikes NE-SW and the younger abutting set strikes NW-SE. These uncomplicated footwall joint-sets reflect the stress field of single-stage, northeast-directed thrusting on the Beartooth fault, and suggest that the stress field record did not include a purely E-W second stage of uplift, as proposed by previous researchers.