Comparative Evolution of Pennsylvanian Platform Margins in Oklahoma and North-Central Texas
CLEAVES, ARTHUR W., and JAMES O. PUCKETTE, Oklahoma State University, Stillwater, OK
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 she f, 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 northeasterly cratonic source, are first seen with Red Fork deposition. Subsequent backstepping of the shelf edge as a consequence of basinal subsidence enlarged the basin at the expense of shelf areas and resulted in deep-water fan deposits accumulating on top of older fluvio-deltaic shelf units. This back-stepping ended during the early Virgilian. Post-Tonkawa cyclic sedimentation prograded the shelf edge southward and gave rise to a more carbonate-dominated shelf sequence. In virtually al instances the regressive submarine fan units indicate eustatic lowstands of sea level.
AAPG Search and Discovery Article #91008©1991 AAPG Mid-Continent Section Meeting, Kansas Geological Society, Wichita Kansas, September 22-24, 1991 (2009)