HR: 1400h
AN: OS23B-09    [Abstracts]
TI: Holocene Infilling History of Tampa Bay, Florida
AU: * Brooks, G R
EM: brooksgr@eckerd.edu
AF: Eckerd College, 4200 54th Ave S, St. Petersburg, FL 33711, United States
AU: Larson, R A
EM: larsonra@eckerd.edu
AF: Eckerd College, 4200 54th Ave S, St. Petersburg, FL 33711, United States
AU: Cronin, T
EM: tcronin@usgs.gov
AF: US Geological Survey, 12201 Sunrise Valley Drive, Reston, VA 20192, United States
AU: Willard, D
EM: dwillard@usgs.gov
AF: US Geological Survey, 12201 Sunrise Valley Drive, Reston, VA 20192, United States
AB: Tampa Bay is a shallow, sediment-starved estuary located along the central Florida Gulf coast. Based upon sedimentologic, biostratigraphic, and geochronologic analyses of 120 sediment cores and 190 surface sediment samples, karst-controlled basins located in the mid to upper estuary were found to contain a continuous sedimentary record documenting the Holocene sea-level rise and infilling history. The basal unit sampled in cores consists of organic-rich and/or carbonate-rich sediments containing freshwater fauna. Interpreted as lake deposits, the surficial sediments of these units were dated at approximately 8-9 ka suggesting that isolated sinkhole lakes occupied the region prior to being flooded by the Holocene sea-level rise. Overlying the lake deposits, dm-scale, organic-rich muds containing brackish water fauna, represent the transition from fresh to marine conditions as sea level flooded the region. The flooding surface itself is generally undefined, but sometimes represented by a mm-scale layer of shell fragments likely representing a lag deposit. Age dates bracketing this layer show that flooding occurred approximately 6-7 ka. Overlying sediments consist of 3-4 m of organic-rich, sandy muds with typical estuarine fauna. Age dates from the base of this unit indicate estuarine conditions became established approximately 5.5-6 ka. The modern expression of karst basins is a series of shallow, bathymetric depressions, likely reflecting the historically slow rate (0.030-0.065 cm/yr) of fine- grained sediment accumulation. These shallow depressions continue to function as fine-grained sediment sinks, but are now rapidly filling as the rate of accumulation has dramatically increased by approximately one order-of-magnitude (0.16-0.32 cm/yr) within the past 100 years, likely due to human activities.
DE: 1641 Sea level change (1222, 1225, 4556)
DE: 4235 Estuarine processes (0442)
SC: Ocean Sciences [OS]
MN: 2007 Joint Assembly