EVOLUTION OF THE WEST-CENTRAL FLORIDA INNER CONTINENTAL SHELF AND BARRIER ISLAND SYSTEM: A REGIONAL PERSPECTIVE ON SEDIMENT ACCUMULATION PATTERNS

This paper addresses regional relationships between the barrier-island system along the west coast of Florida and offshore sedimentary sequences. High population density along this coastline and the resultant coastal-management concerns were primary factors driving the approach of this regional study. Key objectives were to better understand sedimentary processes and sediment accumulation patterns of the modern coastal system, the history of coastal evolution during sea-level rise, and resource assessment for future planning.

In the subsurface, deformed limestone bedrock is attributed to mid-Cenozoic karstic processes. This stratigraphic interval is truncated by an erosional surface, often exposed, that regionally forms the base of the Holocene section. The Holocene section is thin and discontinuous, dominated by low-relief sand-ridge morphologies (0.5 to 4 m’s of relief) with ridge widths on the order of 1 km and ridge spacing of a few kilometers. The sedimentary facies in this system consist mostly of redistributed relic siliciclastics, local carbonate production, and residual sediments derived from erosion of older strata.

Regional trends in sediment thickness patterns are strongly correlated to antecedent topographic control. Both the present barrier-island system and thicker sediment accumulations offshore correlate with steeper slope gradients of the basal Holocene transgressive surface. Proposed models for coastal evolution during the Holocene transgression suggest a spatial and temporal combination of back-stepping barrier-island systems along with open-marine low-energy coastal environments. The present distribution of sand resources and hard-bottom habitats reflect the reworking of these earlier deposits by the late Holocene inner-shelf hydraulic regime.