Tectonic Controls of Late Paleozoic Subsidence in the South Central United States

The Ouachita-Marathon fold and thrust belt has a foreland region in Texas, Oklahoma, New Mexico, and Colorado which was deformed in a style reminiscent of the Laramide foreland in Wyoming and Montana. Large, asymmetric basins are separated by basement block uplifts which were subaerially exposed and eroded during Pennsylvanian and early Permian time. A major, previously unrecognized aspect of this deformation is the regional subsidence which resulted in burial of the uplifts. Analysis of the subsidence history for three basins suggests that crustal extension was not a factor in affecting regional subsidence. This suggestion is in agreement with the presence of a thick crust and reverse and thrust faults in the region. A model is proposed in which northward-directed, low-angle subduction places oceanic lithosphere converted to eclogite beneath the foreland. Resulting isostatic adjustments would have created tectonic subsidence of the same order of magnitude as that observed in the Ouachita foreland.