LATE PALEOZOIC DEFORMATION OF THE PERMIAN BASIN REGION AND OTHER PARTS OF THE MARATHON-OUACHITA FORELAND

The Permian Basin region is a complexly deformed segment of the late Paleozoic Marathon-Ouachita foreland. Transpressional styles of deformation are most common, although transtensional structures are also recognizable. Initial late Paleozoic deformation was broadly distributed across the Permian Basin as a series of asymmetric, north-south-trending anticlines with near-vertical faults cutting the steeper fold limbs. These flower structures largely formed during middle to late Pennsylvanian time. Some in-line faults linked during late Pennsylvanian to Early Permian time and accommodated younger transpressional deformation, whereas many isolated strike-slip structures ceased to grow, especially in areas that later became the Midland and Delaware basins. Fault-linkage along the boundary fault zones of the Central Basin Platform allowed the crustal blocks that comprise this intraforeland high to rotate about vertical axes.

Transpressional and transtensional styles of deformation characterize other parts of the Marathon-Ouachita foreland. Fault-bounded intraforeland highs such as the Central Basin Platform and Wichita-Amarillo Uplift reflect strong transpressional deformation of the foreland at major promontories in the Marathon-Ouachita thrust belt; deeper fault systems were probably reactivated, although direct evidence is lacking. These fault-bounded basement highs trend at high angles to the promontories in the orogen and may have formed because of concentration of bending stresses within the foreland plate. Other faulted late Paleozoic intraforeland highs, such as the Llano Uplift, formed along recesses in the orogen, have fault systems that are subparallel to the orogen, and probably reflect flexural extension across the Marathon-Ouachita foreland.