Abstract: Tampa Bay, Florida: A Carbonate Incised Valley System With Mixed Carbonate/Clastic Fill

Gregg R. Brooks, Larry J. Doyle

Vibracores, surface sediment samples and seismic data show Tampa Bay consists of a system of valleys and isolated basins carved into underlying Tertiary limestones. Sediment fill consists of a combination of terrigenous clastic muds and marine-derived, carbonate-rich sands. Incision and infilling is perceived to have proceeded in four stages during the last sea level cycle. Stage one is characterized by incision of a fluvial valley complex underlying the modern central bay. On the valley flanks limestone dissolution created numerous isolated basins, which currently occupy the modern upper bay. Although presumed to have occurred during the last sea-level lowstand, incision and dissolution probably began during the previous drop in sea level. Stage two represents the initia infilling of the central valley complex with fluvial sands during early transgression. Stage three shows continued infilling of the central valley system with fluvial sands, as well as initial deposition of terrigenous clastic muds in upper-bay dissolution basins. Stage four represents the modern configuration of continued deposition of terrigenous clastic muds in dissolution basins and the incursion of marine, carbonate-rich sands into the lower bay. Relict, fluvial sands remain exposed in the central bay. This modern sediment distribution pattern is unlike those represented in most current models.

Carbonate environments have received little attention in discussions of incised valleys and estuarine fill. Tampa Bay provides an example of these poorly represented features, which should be considered when refining future models.

AAPG Search and Discovery Article #90950©1996 AAPG GCAGS 46th Annual Meeting, San Antonio, Texas