LATE WISCONSINAN AND HOLOCENE DEPOSITIONAL HISTORY, NORTHEASTERN GULF-OF-MEXICO

High-resolution seismic surveys and sedimentologic studies in the northeastern Gulf of Mexico reveal multiple late Quaternary fluvial erosion surfaces. The Apalachicola River, largest river in the northeastern Gulf, incised a network of large channels which today lie buried 5-40 m beneath the present-day inner shelf and the estuary of the modern river. An abundance of coastal and estuarine borehole data enables the seismic records to be quantified to yield paleohydrologic information. The paleohydrologic data show that the Apalachicola was a river of significantly higher discharge before the late Holocene, prior to migrating eastward to its present location. Available evidence indicates that the Apalachicola Delta began prograding in its present location at least 2000 years ago. Much of the near-surface sedimentologic and geomorphologic features of the inner shelf of the northeastern Gulf of Mexico, including perhaps the Florida Middle Ground reef tract, are the result of earlier episodes of migration and delta-building by the Apalachicola River.