Paleozoic structural evolution of the Wichita uplift, southwest Oklahoma

Abstract

Carboniferous intraplate deformation in the southern midcontinent resulted in the formation of several basement-involved uplifts within the foreland of the Ouachita orogen. Offsets across the northern margin of the Wichita uplift, southwest Oklahoma, are measured by palinspastically restoring Silurian-Devonian Hunton Group thickness trends across the Frontal fault zone which separates the Anadarko basin from the Wichita uplift. These reconstructions indicate that displacement along the uplift-bounding faults is predominantly dip-slip and preclude the necessity to involve more than 100 km of left-lateral displacement as suggested by some workers. The Frontal fault zone can be divided into three segments along strike characterized by a younging of deformation form northwest (early Pennsylvanian) to southeast (late Pennsylvanian). Each segment contains evidence for shortening of the sedimentary section in the form of; i) repetition of thick packages of sedimentary rocks along reverse faults, ii) northeast verging first-order folds; iii) steep, basinward-dipping panels of sedimentary rocks between the Frontal fault zone and basin. Deformation in the basement rocks is characterized by displacement along southwest dipping thrusts and reverse faults. The basement profile from uplift to basin is either step-like or consists of a wedge of basement rocks thrust over sedimentary rocks. Balancing of line lengths representing the basement surface and sedimentary units suggests between 5-15 km of shortening occurred across the Frontal fault zone. The presence of a pre-existing (Cambrian) crustal structure influenced the location of the Carboniferous intraplate deformation in southern Oklahoma. A combined tectonic/magmatic model is presented for the initiation of the Southern Oklahoma aulacogen. This model accounts for tilting of igneous laminations within the Wichita Mountains by rotation along southward dipping normal faults. Extension of the crust was compensated by the emplacement of mafic igneous bodies within the upper- and mid-crust. The localization of geophysical anomalies and Cambrian igneous rocks within the boundaries of the uplift implies the placement of the uplift bounding faults was influenced by the Cambrian crustal structure.