THE SOUTHERN OKLAHOMA AULACOGEN: 300 MILLION YEARS OF INTRAPLATE TECTONIC INVERSION INCLUDING REPEATED EPISODES OF HOLOCENE REACTIVATION

The structural framework of southern Laurentia was established in the early Cambrian as the Rodinian supercontinent broke up. The Southern Oklahoma Aulacogen extends across the southwestern U. S. and is a classic example of an intraplate rift that failed during this Cambrian rifting and was massively inverted in the Carboniferous. The scale of Cambrian magmatic modification of the middle and upper crust was very large and was followed by the formation of a 3 km deep post-rift basin, which was in turn followed by a huge (up to 15 km) structural inversion The result is the 15 km deep Anadarko basin that is floored by igneous and basement rocks that outcrop in adjacent uplifts and a major intracratonic structure that is ~1500 km long. The Meers Fault is located on the adjacent Wichita uplift and is the only documented Holocene fault scarp in the North American mid-continent region. It is the southernmost element of the complex and massive (>10 km of throw) frontal fault zone that forms the boundary between the Anadarko basin, which is the deepest intra-continental basin in the United States, and the uplifted igneous rocks exposed in the Wichita Mountains. The most recent movement occurred 1100-1300 years ago with an earlier movement 2,000-2,900 years ago and an even earlier event in the middle-Pleistocene. There is as much as 5 m of vertical displacement and probably appreciably more left-lateral strike slip displacement on the fault. Motion on the Meers Fault represents continued activity on one of the largest structural features in North America. Recently released images from an industry 3-D seismic reflection survey suggest that the Meers fault is located on a major deep-seated structure and is potentially an inverted normal fault of Cambrian age.