STRUCTURAL EVOLUTION OF THE ARKOMA FORELAND BASIN, OKLAHOMA

The Arkoma basin is a foreland basin of the Ouachita fold and thrust belt which formed in Late Paleozoic due to the continent-continent collision between North America and South America. It contains about over 30,000 feet thick Pennsylvanian Flycsh and Molass deposits underlain by 5,000 feet thick Middle Cambrian to Late Mississippian miogeoclinal rocks. The Flycsh deposits were accumulated in a basin bounded by northward advancing thrust sheets to the South, Pennsylvanian Continental margin of North America to the North and Pennsylvanian Appalachian Mountains to the Northeast. The Flysch deposits were deformed during the Pennsylvanian Ouachita Orogeny.

The Silurian Woodford Shale contains a major detachment surface on the Ouachita fold-thrust belt. In the Potato Hills area of the Central Ouachitas, 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 portioning is accommodated by imbricate fan thrusts on the hanging wall Choctaw detachment. 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 Flycsh is well exposed in both hanging wall and footwall of the Choctaw detachment. 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 zone. 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 Detachment.