Influence of Drainage Basin Attributes on Depositional Style of the Upper ÒMorrowÓ and ÒCherokeeÓ Intervals, Oklahoma

Jim Puckette. School of Geology, Oklahoma State University, 105 NRC, Stillwater, OK  74078, phone: (405) 744-6358, fax: (405) 744-7841  [email protected]

A comparison of northerly sourced Pennsylvanian sediment dispersal systems of the upper ÒMorrowÓ and ÒCherokeeÓ intervals reveals distinct differences in depositional style. These differences may be attributed to drainage-basin attributes and climate. The upper Morrow drainage basin was defined to the north by the Central Kansas uplift, Cambridge Arch, and Ancestral Rockies, all sources for basement detritus. The remaining drainage basin was located on easily disaggregated and soluble sedimentary rocks including cherty carbonates. In contrast, Cherokee dispersal systems emanated from a large drainage basin that extended to the Canadian Shield. Weathering of shield basement rocks provided quartz, feldspar, and metamorphic rock fragments characteristic of Cherokee sandstone detrital composition.

Drainage basin size and paleogeology influenced sediment supply. The Cherokee sediment-dispersal systems were supplied with large volumes of sand derived from shield rocks. Large deltaic complexes formed and were incised by fluvial systems. Valley fills contained stacked fluvial sands. Marine influence within valleys was limited and typically restricted to uppermost portions of the fill.

Deltaic complexes are absent in the upper Morrow. Available sediment was dominantly mud weathered from sedimentary rocks. As a result, the incised valleys that formed were undersupplied with sand. Lowstand deposits within these valleys were thin, channel-lag gravels. The limited volume of sand-sized and larger sediment transported across the shelf was diluted with mud and dispersed. During transgression, sand was trapped in valleys but did not fill them. Cores of valley fills contain evidence of estuarine and marine incursions that ultimately dominated deposition in the upper valley fills.