65 Structural Geology / Tectonics (Posters)

Tuesday, 25 March 2014
8:00 AM - 12:00 PM
Freedom Hall A

KINEMATIC AND STRUCTURAL DEVELOPMENT OF CRAZY WOMAN MOUNTAIN, BIGHORN MOUNTAINS, WYOMING

Paper number: 65-6
Program: Technical Sessions
Time: 8:00 AM – 12:00 PM

Authors

  • Andrew D. Clift Presenting Author
    South Dakota School of Mines and Technology, Rapid City, SD

Abstract

Crazy Woman Mountain is located in Johnson County, Wyoming, along the eastern front of the Big Horn Mountains. Geologic mapping shows that the stratigraphy consists of Paleozoic rock units overlying a crystalline Precambrian basement. Structural development suggest a basement involved fault-propagation fold resulting in over 2,000 feet of structural relief, and a prominent north-northeast trending, southeast vergent monocline, with shortening to the east-southeast. Three domains are recognized based on distinct bedding geometries, and are used to constrain different stages of Laramide deformation.

Unrotated fault-slip data indicate a series of en echelon high-angle sinistral strike-slip faults along the eastern front of the monocline, which suggest partitioned faulting during a regional oblique dextral strike-slip. A hypothesis that gravitational collapse was the mechanism behind southeast vergence of the monocline was tested. Kinematic solutions indicate southeast compression, however fault plane geometries do not support the gravitational collapse hypothesis. Paleostress orientation determinations are compatible with principal strain axes. Rotated data sets were analyzed to constrain the timing of deformation. A comparison with rotated fault-slip data indicates the kinematics fit best with unrotated data and that late stage fracturing is associated with regional Laramide stress orientations.