Lithofacies, depositional environment, and stratigraphic architecture of the deep-water hybrid mudrock system of the Pennsylvanian (Desmoinesian) Cherokee Group, Anadarko Basin, Texas Panhandle
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The Cherokee Group in the western Anadarko Basin, northeastern Texas Panhandle, is a Desmoinesian hybrid system of mudrocks interbedded with sandstones and carbonates in a deep- water foreland basin that had poor circulation with the open ocean. The cyclic sedimentation and foreland basin tectonics resulted in a complex stratal architecture that was sourced by multiple areas of sediment input. Previous studies of the Cherokee Group focused on age-equivalent strata in Oklahoma and Kansas. This study uses six cores and 1980 wireline logs to characterize facies and their distribution, interpret depositional environment, and construct regional stratigraphic framework. Wireline logs were correlated in the area of over 9500 sq km to map out six depositional packages that are separated by major flooding events. These events are correlative over the whole area of study. Lithofacies are recognized based on depositional features and mineralogy: (1) mud-clast conglomerate, (2) muddy matrix conglomerate, (3) sandy siliciclastic conglomerate, (4) massive sandstone, (5) planar-laminated to ripple cross-laminated sandstone, (6) laminated calcareous to siliceous mudstone, (7) very thin to thin- laminated argillaceous mudstone, (8) massive to faintly laminated siliceous mudstone, (9) disorganized and/or disturbed laminated mudstone, (10) grainstone and grain-dominated packstone, and (11) peloidal packstone. The integration of isopach maps of depositional packages with the lithofacies allowed the delineation of the spatial and temporal evolution of the slope to basin-floor system. The Cherokee benthic biota was transported to the basin from the shelf or oxygenated upper slope by gravity flows. Biogenic planktonic sediment was sourced from water column. Deposition of the sandstones and carbonates are by turbidity currents, slurry flow, debris flow, and mud flow. Fine-grained sediments were transported by turbidity currents or by hemipelagic settling. The deposition of the Cherokee Group in the study area occurred under dysaerobic to anaerobic bottom conditions developed below storm-wave base and below the oxygen-minimum zone as evidenced by rare bioturbation, low fauna diversity, high TOC, and high Mo content in the mudrock facies.