Comparative Evolution of Pennsylvanian Platform Margins in Oklahoma and North-Central Texas

Abstract

Pennsylvanian evolution of the Midland basin's eastern shelf and the northern shelves of the Anadarko and Arkoma basins demonstrates a strongly contrasting pattern with regard to the facies composition and stability of the shelf margin. For the Midland basin a carbonate ramp system developed adjacent to the Eastern shelf during the early Desmoinesian but received no coarse-grained clastic sediment until after the central Fort Worth basin was completely filled by Ouachita orogenic debris in the late Desmoinesian. At that time, a distinct north-south hingeline formed between the shelf and incipient Midland basin that allowed for subsequent vertical accretion of a Missourian-age double bank system. Due to the absence of active deltaic depocenters across the southern two-thirds of the shelf, the Missourian shelf margin did not prograde basinward nor did a submarine fan system develop adjacent to this reciprocal bank complex. Later, during the Virgilian, a single shelf-edge bank and submarine fan complex prograded the shelf edge westward. The shelf edges for the Anadarko and Arkoma basins demonstrate a significantly different pattern. Only during the late Desmoinesian (Marmaton Group) did a shelf-edge bank develop in association with shelf-slope reciprocal sedimentation. For the Anadarko basin, widespread submarine fans, fed from a northeasterlymore » cratonic source, are first seen with Red Fork deposition. Post-Tonkawa cyclic sedimentation prograded the shelf edge southward and gave rise to a more carbonate-dominated shelf sequence. In virtually all instances the regressive submarine fan units indicate eustatic lowstands of sea level.« less