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The AAPG/Datapages Combined Publications Database

GCAGS Transactions


Gulf Coast Association of Geological Societies Transactions
Vol. 51 (2001), Pages 109-120

Fluvial Sedimentation in the Cotton Valley Group in Stringer Field, Jasper County, Mississippi

Ezat Heydari, Roger N. Townsend


The Cotton Valley Group exhibits a wide variety of depositional systems in the north-central U. S. Gulf Coast. The group is best studied in northern Louisiana and southern Arkansas where it displays a barrier island-lagoon-fluvial complex. East Texas Cotton Valley shows a fan-delta system. Detailed regional variations in lithofacies and depositional systems of this unit have not been documented in Mississippi, where only one formation (Schuler Formation) has been assigned to this group, attributed broadly to deltaic sedimentation. Close examination of conventional cores from six wells at Stringer Field in Jasper County provides a glimpse into the lithofacies successions and depositional systems of the Cotton Valley Group in this area.

Cores are primarily from the uppermost Middle Member of the Cotton Valley Group and display fining upward successions of lithofacies. The successions generally begin with carbonate conglomerate or coarse sandstone layers that are overlain by cross-laminated sandstones, and terminate with red or gray mudstones exhibiting features resembling plant roots and containing carbonate nodules. These fining upward successions of lithofacies indicate meandering river depositional systems. The conglomerate layers were deposited as channel lag and gravel bars, the cross-laminated sandstone formed in a point bar and/or mid-channel bar, and rooted mudstones represent flood plain deposits. The internal structures of carbonate fragments of the conglomeratic layers suggest that these particles were originally formed as nodules in soil zones in the adjacent flood plain areas and were subsequently incorporated into channels during river migration. The regional significance of the fluvial system described in this uppermost portion of the Middle Member of the Cotton Valley Group is unclear at this point. This fluvial environment could belong to a more regional terrestrial sedimentary system or to an upper delta plain. Other questions include the nature of time equivalent environments to the north (landward) or to the south (seaward) of Stringer Field. Further studies are needed to resolve these questions.

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