TECTONICS, VOL. 8, NO. 5, PAGES 1015-1036, OCTOBER 1989 STRUCTURAL EVOLUTION OF THE ARDMORE BASIN, OKLAHOMA: PROGRESSIVE DEFORMATION IN THE FORELAND OF THE OUACHITA COLLISION James W. Granath • Exploration Research and Services Division, Conoco Incorporated, Ponca City, Oklahoma Abstract. Synthesis of oil field studies, seis- mic reflection data, and surface geology has re- sulted in a reconstruction of the Pennsylvanian evolution of the structural style of fault systems bordering and within the Ardmore Basin in south central Oklahoma. Faults bounding the mar- gins of the basin were part of a broader left- lateral shear belt that affected southern Okla- homa during the early Pennsylvanian. The mid- Pennsylvanian and later zone of deformation con- tracted in southern Oklahoma to concentrate on the Washita Valley-Eola Robberson fault sys- tems along the northern edge of the basin, and on the Criner Uplift-Healdton-Stephens County fault systems along the southernand westernside of the basin. Deformation on the floor of the basin was amplified, with left-lateral strike-slip faults slicing the basin into a system of rhom- bohedral blocks. Deformation continued at least into Virgil time (late Pennsylvanian). A two- dimensional displacement field derived for the middle to late Pennsylvanian deformation re- veals that a strong component of transpression affected both the basin-bounding faults and, by reason of the geometry of their connections to the west, the Wichita Mountain front as well. •Now at Worldwide Exploration Services, Conoco Incorporated, Ponca City, Oklahoma. Copyright 1989 by the American Geophysical Union. Paper number 89TCOO563. 0278-7407 / 89/89T C-00563 $10.00 Broadly spread left-lateral shear evolved into crustal scale transpression during the Pennsyl- vanian Period. That progressivecontraction of deformation and the change in style correlate with mid-Pennsylvanian approach and passage of the Ouachita collision along the Ouachita em- bayment (Thomas, 1983)on the southern margin of the North American craton. Inasmuch as the Ardmore Basin was located at the sharp internal corner of the embayment, the coincidence sug- gests that the style of evolution records (1) early far-field influence of the approaching Ouachita collision during earlyPennsylvanian, (2) passage of the suture during mid-Pennsylvanian, and (3) concentration of foreland deformation at the cor- ner of the embayment as the Arkoma and Fort Worth flexural basins evolved to the south and east during late Pennsylvanian. INTRODUCTION The Ardmore Basin is a fault-bounded basin of Pennsylvanian age in south central Oklahoma. It developed in concert with the emplacement of the Ouachita fold and thrust belt on the edge of the North American craton [Ham and Wil- son,19671 and consequently, is relatedin time to a number of Pennsylvanian to Permian tectonic features scattered throughout the southwestern UnitedStates [Kluth and Coney 1981].The Ard- more Basin lies within the foreland immediately adjacent to the fold and thrust front (Figure 1) and is confined to the floor of a lower Paleozoic depositional trough that has come to be known as the Southern Oklahoma Aulacogen [Shatski, 1947; Burke andDewey, 1973; Burke,19771 . The