Sequence-stratigraphic context of Pennsylvanian (Desmoinesian-Missourian) siliciclastics: Cleveland Formation and Marmaton Group, western Anadarko Basin, Texas panhandle

Upper Desmoinesian and lower Missourian siliciclastic strata of the western Anadarko Basin compose a Midcontinent cyclothemic succession that was influenced by both eustatic variation and local, pronounced tectonism during deposition. Mostly westerly sourced fluvial and deltaic/strandplain systems of this interval accumulated in coastal plain, marine-shelf, and proximal shelf-slope settings within the western Anadarko Basin of the northeastern Texas Panhandle. Sequence 1 is characterized by landward- and seaward-stepping facies patterns on well logs and in cores that define (in ascending order) Marmaton lowstand-wedge and transgressive systems tracts (TST) and a lower Cleveland highstand systems tract. A regionally correlative, organic-rich, and phosphatic black shale (condensed section) at the top of the Marmaton TST represents a eustatic maximum at the end of the Desmoinesian. A relative sea-level drop with the onset of Sequence 2 deposition initiated development of a sand-rich incised-valley system that traversed the Cleveland coastal plain and depositional shelf for more than 135 km. Subsequent coastal onlap by thin deltaic systems of the overlying TST marks the start of decreased sediment influx during late Cleveland time, resulting in thinning of parasequences and an increase in carbonate beds in upper Sequence 2 and Sequence 3. Because of its distinctive faunal assemblage, themore » top-of-Marmaton condensed section can be correlated with the Nuyaka Creek black shale bed of the Midcontinent shelf; this bed represent a major eustatic transgressive phase. This correlation and the systems-tract framework of the Marmaton/Cleveland interval provide a starting point for developing a more detailed interregional sequence-stratigraphic tie between the Anadarko Basin and Midcontinent shelf.« less