RECENT SEDIMENTARY DEVELOPMENT OF TAMPA BAY, FLORIDA - A MICROTIDAL ESTUARY INCISED INTO TERTIARY PLATFORM CARBONATES

Tampa Bay, a large, microtidal, clastic-filled estuary incised into Te rtiary carbonate strata, is the largest estuary on Florida's west coas t. A total of 250 surface sediment samples and 17 cores were collected in Tampa Bay in order to determine the patterns and controlling facto rs governing the recent infilling and modern sediment distribution, an d to examine the results in terms of current models of estuarine sedim entation and development. Surficial sediments in Tampa Bay consist of three facies types, each occurring in a distinct zone: modern terrigen ous elastic muds occurring in the upper bay and around the bay periphe ry; relict, reworked-fluvial, quartz-rich sands occupying the open por tion of the middle bay; and modern carbonate-rich, marine-derived sand s and gravels occupying the lower bay. Factors controlling sediment di stribution include: sediment source and supply rate; bathymetry, which is a function of the antecedent topography; and the winnowing effect of wind-generated waves that prohibits modern accumulation in the shal low middle bay. These factors also play a major role in the recent inf illing history of Tampa Bay, which has progressed in four stages durin g the Holocene sea-level rise. Recently developed models of estuarine sedimentation are based primarily on mesotidal to macrotidal estuaries in terrigenous elastic settings in which sedimentation patterns and i nfilling history are a result of the relative contribution of marine a nd fluvial processes. Tampa Bay differs in that it was originally inci sed into carbonate strata, and neither fluvial or marine processes are interpreted to be major contributors to modern sediment distribution. Tampa Bay, therefore, provides an example of an unusual estuary type, which should be considered in future modeling efforts.