Interpretation of the Reagan Fault, Garvin, Johnston, Murray, and Stephens Counties, Oklahoma

Abstract

The Reagan fault, which lies between the Mill Creek syncline and the Tishomingo anticline, is one of the major faults in the Arbuckle Mountains. The fault's surface expression extends for more than 24 mi, and it can be traced in the subsurface at least an additional 26 mi west. The relative upthrown side of the fault changes at least four times along its length and it is manifest in different segments as both an apparent reverse fault and an apparent normal fault. Subsurface cross sections show abrupt facies changes within formations across the Reagan fault and isochore maps of individual units indicate a large-scale component of left-lateral movement along the fault. The geometry of the fault, as well as its displacement, also is consistent with a wrench-fault interpretation of the Reagan fault. Synorogenic conglomerates indicate that in at least one locality the Reagan fault had ceased movement, whereas the Washita Valley fault was still active.