ANDERSON, HEATHER E., Louisiana State University, Baton Rouge, LA; and PHILIP J. BART, Louisiana State University, Baton Rouge, LA

Abstract: Evolution of the Apalachicola Delta During the Last Glacial Eustatic Cycle

A study of the Apalachicola fluvial-deltaic system is part of a larger study covering the Northern Gulf of Mexico. The studies are being conducted to determine the response of different systems to changes in sea level and climate or fluvial geomorphology during the last glacial eustatic cycle. The Apalachicola system is unique for its ramp-type margin, relatively low subsidence, and drainage basin characteristics. The drainage basin of the Apalachicola system has significant relief with numerous perennial tributaries and a minimal distance separating Pleistocene uplands from the coast, compared with the Colorado and Brazos fluvial systems of Texas. As a result, the alluvial valley is deeply incised. Sediment delivered to the shelf is dominated by sands. During the summer of 1998, approximately 500 km of high resolution seismic data was collected on the middle and outer shelf of west Florida. Delta lobes have been mapped along the shelf with relative ages constrained by the oxygen isotope/sea-level curve. Seismic facies analysis shows large (up to 500 square km wide and 70 m thick), sand dominated delta lobes on the shelf.

Delta lobes occur within highstand, lowstand, and transgressive systems tracts. Progressive seaward shifts in the delta during the falling limb of sea level suggest a continuous sediment supply to the shelf. Sediment supply was more episodic during the transgression. A more precise history of delta evolution is currently under investigation.

AAPG Search and Discovery Article #90924©1999 GCAGS Annual Meeting Lafayette, Louisiana