The En Echelon Arrangement Of Two Basement Involved, Low-Angle Thrust Faults In The Owl Creek Mountains, Wyoming

John Jostes

The Owl Creek Mountains, located in central Wyoming, constitute an east-west trending uplift forming the boundary between the Wind River and Bighorn Basins. Individual structures on the Owl Creek Mountains trend northwest-southeast on the east-west grain. In general, the uplift is an asymmetric anticlinal form cored by Precambrian basement.

The North Mud Creek and Owl Creek Anticlines are structural features located in the Owl Creek Mountains. These anticlinal structures are asymmetric folds on the footwall of the North Owl Creek Fault located southwest of the study area. The North Owl Creek Fault is a complex zone of interconnected faults with fault bounded slivers of Paleozoic rocks. Development of these anticlines are the result of southwest and northeast verging basement involved low-angle thrust faulting. Field evidence suggests that the mountain block has moved easterly and upward, in a left-oblique sense with respect to the adjacent Bighorn Basin. Kinematic indicators also suggest that North Mud Creek and Owl Creek anticlines moved slightly westward or southwestward, in agreement with the inferred sense of motion f the Owl Creek uplift.

The North Mud Creek and Owl Creek anticlines are both northerly plunging anticlines that have an en echelon relationship. This structural arrangement is the result of two separate basement thrust faults verging towards one another. The movement of the Embar anticline west of the study area influenced the two anticlines by compressing and forcing the entire area eastward.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California