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The AAPG/Datapages Combined Publications Database

GCAGS Transactions

Abstract


Gulf Coast Association of Geological Societies Transactions
Vol. 41 (1991), Pages 60-71

Distribution Patterns and Accumulation Rates of Fine-drained Sediments in Upper Tampa Bay, Florida

Gregg R. Brooks (1), Larry J. Doyle (1), Roger Johansson (2), Andy Squires (3), Hepsi D. Zsoldos (1), Robert H. Byrne (1)

ABSTRACT

Tampa Bay, a drowned river valley, is the largest estuary on Florida's west coast, and almost completely surrounded by heavy urban development. A series of eleven sediment cores and high resolution seismic reflection data as collected in Hillsborough Bay, the northeast lobe of Tampa Bay, in order to determine the processes controlling sediment distribution patterns and accumulation rates throughout the recent geologic past.

Surface sediments consist of a mixture of carbonate and terrigenous clastic sands and muds. Mud-size sediments in the open bay are concentrated in low energy bathymetric depressions. Accumulation rates determined by carbon-14 methods for the past several thousand years average 31-49 cm/1,000 years. Rates for approximately the past 100 years, determined by 210Pb and 137Cs methods, range from 0.13 to 0.42 cm/year. Sediment texture, gross mineralogy and organic content show no major variations, but a weak tendency toward increasing organic and carbonate contents, and an accompanying decrease in grain size in the upper 20-30 cm of some cores suggests that there may have been an alteration in sedimentation patterns beginning approximately 100 years ago.

Results indicate a major control on the distribution of fine-grained sediments in Hillsborough Bay is bathymetry, as broad, shallow depressions have acted as fine-grained sediment sinks for the past several thousand years. The apparent recent increase in accumulation rate, as well as observed alterations in sedimentation patterns beginning approximately 100 years ago, is consistent with early urban development of the Tampa Bay area.


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