INFLUENCE OF PROVENANCE AND SEDIMENT SUPPLY ON DEPOSITIONAL STYLES OF THE PENNSYLVANIAN UPPER MORROWAN AND "CHEROKEE" INTERVALS, OKLAHOMA

The Pennsylvanian (Desmoinesian) Bartlesville, Red Fork, Skinner and Prue sediment dispersal systems were large fluvio-deltaic complexes that prograded southward toward the Arkoma and Anadarko basins. Sands deposited within these complexes contain a variety of depositional features, geometries and distribution patterns indicative of channel, delta-fringe and delta-plain environments. During sea-level lowstand, Red Fork sediment was transported across the exposed shelf of the Anadarko basin and deposited on the basin floor as submarine fan complexes. Sediment supply was abundant and large volumes of sand accumulated on the basin floor. Cherokee sandstones in all settings are quartz rich and contain a significant percentage of metamorphic rock fragments.

The upper Morrowan interval on the northern shelf of the Anadarko basin is remarkably different from the Cherokee. There is no evidence of extensive delta fringe or delta plain sedimentation. Sandstones occupy linear trends interpreted as valley fills. Almost all sand bodies were confined to these valleys. Channel fills contain evidence of increased marine influence toward the top. Morrowan sandstones are devoid of metamorphic rock fragments, but rich in chert, microcline and plutonic rock fragments such as microperthite and granophyre.

It is proposed that drainage basin size and surface paleogeology influenced sediment supply. Cherokee fluvio-deltaic complexes were well supplied with large volumes of sand derived from shield rocks. As a result, Cherokee channel fills are dominated by stacked fluvial sands. Marine influence is minimal and limited to the very uppermost portions of the fill.

In contrast, upper Morrow valleys appear to be undersupplied with respect to fluvial sediment. Lowstand deposits are represented by thin, pebble and clay-clast, channel-lag conglomerates. The limited volume of sand-sized and larger sediment transported across the shelf was dispersed and diluted with mud in the Morrowan sea. During transgression, essentially all sand was trapped in the valleys. However, the limited volume of fluvial sand was not adequate to fill valleys and estuarine and marine deposits are dominant in the upper portions of valley fills.