LATE HOLOCENE SEA-LEVEL CHANGE AND DELTA MIGRATION, APALACHICOLA RIVER REGION, NORTHWEST FLORIDA, USA

Late Holocene environmental changes in the lower Apalachicola River re gion of northwest Florida appear to be a consequence of deltaic lobe-s hifting and sea-level change. Sedimentological, archaeological and sei smic evidence all indicate a major eastward shift in deltaic depositio n approximately 6,000 years ago, when construction of the modern Apala chicola Delta began. The effect is observed in the mid-region of the m odern delta as a pronounced change from estuarine to freshwater condit ions during the mid- to late Holocene. Enclosing the modern delta and estuary is a barrier island chain which began to develop about 4,000 y ears ago. A change in depositional pattern over time is evident in the barriers, possibly as a response to the continuing eastward shift of the delta. Archaeological evidence from the barriers indicates a minor higher-than-present sea level during the late Holocene. The timing of the high stand is consistent with evidence from other locations in th e Southeastern United States.