ARKOMA FORELAND BASIN OF THE PENNSYLVANIAN OUACHITA OROGENY, EASTERN OKLAHOMA AND WESTERN ARKANSAS

The Arkoma Foreland basin was formed in Late Paleozoic due to the continent-continent collision between North America and South America. The basin extends from south-central Oklahoma to Central Arkansas where it is covered by Cretaceous sediments. It contains approximately 10,000 meter thick Pennsylvanian sedimentary rocks which are underlain by more than 1,500 meter thick Middle Cambrian to Late Mississippian Miogeoclinal rocks. In Pennsylvanian, sediments were accumulated in a basin bounded by northward advancing thrust sheets to the south, continental margin of North America to the north and the Appalachian Mountains to the east and northeast. Syn and post depositional deformation of sediments took form during the Pennsylvanian Ouachita Orogeny.

The Choctaw fault is the leading-edge thrust of the Ouachita fold-thrust belt. It separates highly deformed rock of the Ouachitas from the mildly deformed rocks of the Arkoma Basin. Several detachment surfaces are responsible for contractional deformation in the Ouachitas and the Arkoma Basin. In the Potato Hills area, the Middle Ordovician to the Mississippian rock units are exposed at the surface. In the subsurface, however, the Woodford detachment is the floor thrust and the Choctaw detachment is the roof thrust of an antiformal stack structure which involves Pennsylvanian rock units. From the central Ouachitas to the leading edge of the frontal Ouachitas, strain partitioning is accommodated by imbricate fan thrusts on the hanging wall of the Choctaw fault. The strain partitioning is accommodated primarily by a triangle zone and associated duplex structure in the frontal Ouachitas-Arkoma Basin transition zone where the Atokan sedimentary rocks are present in hanging wall and footwall of the Choctaw fault. The duplex structure is located between Springer detachment (the floor thrust) and the Lower Atokan detachment (the roof thrust) in the footwall of the Choctaw fault. The triangle zone is floored by the Lower Atokan Detachment and flanked by the Choctaw fault to the south and the Carbon fault to the north. When restored to their original position prior to lower Atokan the cross-sections indicate about 60% shortening from the Central Ouachitas to the Arkoma Basin. The shortening is, however, only about 25% in the Arkoma Basin in the footwall of the Choctaw fault.