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The AAPG/Datapages Combined Publications Database

GCAGS Transactions

Abstract


Gulf Coast Association of Geological Societies Transactions
Vol. 39 (1989), Pages 341-347

Origin and Development of Quaternary Terrigenous Inner Shelf Sequences, Southwest Florida

Richard A. Davis, Jr., Jonathan M. Klay (1)

ABSTRACT

The Quaternary stratigraphic record on the inner shelf off the coast of southwest Florida between Cape Romano and Cape Sable is quite thin. The gradient of this coast is and has been, extremely low; about 1:3000. The combination of coastal configuration, available sediments and processes have resulted in a stratigraphy which reflects the diverse depositional environments that have occupied this region for the past several thousand years. Overall energy levels have been low throughout most of the period when this record accumulated. A combination of relatively high-energy tidal processes and low-energy wave-dominated processes has produced a distinctly different sequence on part of this shelf during the Holocene.

The pre-Holocene stratigraphy includes a karstic Plio-Pleistocene limestone surface overlain by a muddy, low-energy coastal sequence of terrigenous sands. The lower Holocene strata represent the transgressing protected and partially vegetated open marine environments from about 7,000 - 3,000 years B.P. when sea level was rising slowly over this broad shelf. Sea level has been near its present level for the last 3,000 years during which this inner shelf environment has changed dramatically.

During the past few thousand years or less, the sequence that has accumulated on this shelf area is largely restricted to the northern portion of the area. The Gulfward portion of this area is characterized by tide dominated sand ridges which are similar but smaller than those in the North Sea. Landward of these ridges in Gullivan Bay is a sequence of muddy sands which represent a sediment sink in a protected, low energy area. The southern two-thirds of this inner shelf system lacks significant terrigenous Quaternary sediments due primarily to a lack of supply.


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