Abstract

The paired uplifts and depositional basins of the Wichita lineament, which trends northwest across southern Oklahoma, were recognized by the Soviet geologist Shatski as the most obvious North American example of an aulacogen. These long-lived, deeply subsiding, and often fault-bounded features result from thermal doming of continental lithosphere, produced by plume-generated uplifts, which rupture the crust in three rifts at mutual angles of about 120°. Two of the rifts open by plate accretion to form an ocean basin while the third, extending at high angles from the newly rifted margin far into the plate interior, becomes inactive as a “failed arm” or aulacogen.

These features, of which the Afar region linking the Red Sea, Gulf of Aden, and the Ethiopian rift system is a modern example, begin as narrow fault-bounded grabens and later become broader downwarps. Intermittent basaltic and rhyolitic volcanism often characterizes the early stages of formation, and later tectonic events often produce compressional folds and faults important to the accumulation of hydrocarbons.

The Wichita aulacogen, long known as the Southern Oklahoma geosyncline, developed on a Precambrian granitic basement. This failed-arm trough received nearly 20,000 ft. (6,061 m) of graywacke, bedded chert, spilitic basalt, rhyolite, and hypabyssal sills. Late Cambrian to Devonian subsidence localized deposition in the trough of as much as 9,500 ft. (2,879 m) of carbonate strata, a much greater thickness than is found on the adjacent platform.

Continental collision began to affect the area in Carboniferous time, as the Afro-South American plate converged on North America to form Pangaea. Compressive stresses initiated by this collision were transmitted far into the continental interior along the reactivated basement faults. Both vertical and transcurrent movement on these faults gave rise to a complex system of paired uplifts and fault basins, such as the Arbuckle Mountains-Ardmore basin and the Wichita Mountains-Anadarko basin.