Colin Plank¹, Christopher G. St. C. Kendall¹
(1) Department of Geological Sciences, University of South Carolina, Columbia, SC

Abstract: Plio-Pleistocene shelf edge delta system models applied to the Northern Gulf of Mexico

Northern Gulf Plio-Pleistocene stratigraphy is characterized by a unique combination of depositional styles and syndepostional structure. Unstable wave dominated shelf edge deltas, associated with later portions of lowstand system tracts, rapidly prograded under the influence of fourth order (5 Ma or less in duration) sea level fluctuations and large sediment loads derived from glacial runoff. As progradation neared the shelf edge, arcuate systems of growth faults developed, forming potential traps for coarse sediment. Using industry donated 3D seismic data, well logs, and public domain biostratigraphy, a small portion of a shelf edge delta system was studied in the Eugene Island 300 area of offshore Louisiana, placing it in the context of current depositional models developed for the Northern Gulf. Six "fourth" order sequences, from 1.5 to .5 Ma, were identified and correlated across the study area, dominated by three northeast trending growth faults. At this time delta front and lower delta plain settings were prevalent in the area. Slope and deeper water systems were not present in the interval studied. Inception of the northern most fault in the area coincided with sedimentary loads delivered at the beginning of the Yarmouthian interglacial period (approximately 1.5 Ma). Fault movement continued, at times sporadically, throughout the deposition of all interpreted sequences. This resulted in stratal thickening, characteristic of the Northern Gulf. Though sediment accommodation increased across each fault, little evidence supports that these faults controlled depositional morphology; revealing the scale of the shelf deltaic system while helping refine depositional models for this setting.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana