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ABSTRACT: Details of South Lake Arthur Field--Isopachous Maps and Log Correlations Utilizing Depositional Ideas

Joseph M. Battle, Jr.

Continued development of South Lake Arthur field, Vermillion Parish, Louisiana, has given geologists some apparent answers as to the true nature of the productive "Miogyp" feature--that it is a large, structurally simple, pressure connected, east-west oriented anticlinal structure developed on the downthrown side of a major east-west, down to the coast, growth fault system.

South Lake Arthur field is a structurally simple feature, the stratigraphic sequence of which ideally fits the unstable-shelf delta model. Deposition of a thick sequence of plastic prodelta shales immediately preceded a major regressive Miogyp delta complex. Component sand bodies within this complex conform paleogeographically to the model, with a central "depopod" of distributary mouth bars, flanked seaward by beach sands, and capped by a classic reworked sand. The Miogyp delta system built for a long duration of time owing to rapid subsidence associated with the dumping of a thick sediment load on the downthrown side of a large down to the coast growth fault, and flowage of the underlying shale.

Although South Lake Arthur field is structurally simple, the Miogyp through Camerina section is stratigraphically very complex. "Paleostructural" analysis, using interval isopach maps, is necessary to properly interpret this section. Interval isopach maps reveal correct depositional-strike, or paleo-strike, correlations. These isopach maps also depict a stratigraphically complex growth history of the South Lake Arthur field structure. Shifting depositional patterns and unconformities all relate to the movement of the plastic core of the prodelta shale underlying the Miogyp distributary mouth bar complex.

AAPG Search and Discovery Article #90999©1990 GCAGS and Gulf Coast Section SEPM Meeting, Lafayette, Louisiana, October 17-19, 1990