This study shows the possibility of extensive lateral movement along pre-Permian faults in the Permian basin and determines, largely from subsurface evidence, the direction of the forces responsible for Pennsylvanian and Permian tectonic deformation. A review of the relation of faulting to orthogonal stress axes shows that changes in the geometry and genesis of faults are the consequences of changes in the orientation of the stress axes.

Two tectonic systems can be discerned. One consists of folds and faults. The fold axes strike N35°W, whereas the fault systems include one that strikes N55-80°E with indications of right lateral movement and another that strikes N50-65°W with left lateral movement. Thus the fault pattern indicates stress in a nearly east-west direction and the folds indicate direction of stress to be about N65°E. The age of this deformation is thought to be early Late Mississippian to late Middle Pennsylvanian.

Another fault system which seems to be younger is composed of faults striking slightly west of north. The most prominent example of this system is the West Platform fault, the movement on which is right lateral with a displacement of tens of miles. The stress giving rise to this system seems to have been nearly north and south and may be related to the force that powered the early and middle Wolfcampian (Permian) thrusting on the south in the Marathon salient of the Ouachita belt. The jagged pattern of the eastern edge of the Central Basin platform may be caused by conjugate faults of this system.

The later tectonic history of the region is marked by relaxation of stress and subsequent normal fault movement on the previously formed fault planes. This movement deepened preexisting basins; reefs and other sedimentary features formed around the peripheries of these depressions. Formation of salt pans in later Permian time was related to minor movement along the faults. Remnants of the basins persisted throughout Triassic time, but were obliterated by the great change in geography during Cretaceous time. Renewed movement along the old lines of weakness during Tertiary time caused the eastward tilting of the Delaware basin and the formation of grabens along its west edge. Deep channels in Pleistocene and Holocene sand deposits in the eastern part of the Delaware basin reflect soluti n of the underlying Permian evaporites over these lines.