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U.S. Department of the Interior
U.S. Geological Survey
Open-File Report 01-422 [View PDF]
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View other reports in the 2001
Tampa Bay Pilot Study Series: |
| 1-2-3-4-5-6-7-8-9 |
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Task Leader: Terry Edgar
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Tampa Bay Integrated Science Pilot Study:
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Historical and prehistorical record of Tampa Bay Environment
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Approach
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Coring bay and wetland sediment:
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- The best method to identify prehistoric environments is to collect and analyze sediment cores. Cores provide samples from the oldest time (at the bottom) to the youngest (at the top).
- Date cores using 210Pb, 14C, and Optical Stimulation Luminescence,
- Determine nature of upland and bay flora using biomarkers and pollen,
- Measure salinity of pore waters,
- Determine change in salinity of bay waters resulting from rising sea level and changes in climate using microfauna,
- Evaluate pollutant content of cores from ICP 40-element analysis and elemental Hg concentration.
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Core sites were selected in two general areas:
- less disturbed natural site, and
- highly inpacted area.
Mariposa Point (Moses Hole) in the Terra Ceia area was chosen for a record of the bay’s environment in an area least disturbed by historical activities, and Hillsborough Bay (within Alafia River area on Fig. 1), where the historical effect is expected to be high. Mariposa Point was specifically identified as a focus for combined geological, biological, and geophysical studies. It is largely a mangrove-dominated area of southwestern Tampa Bay that is punctuated with shallow sinkholes created in underlying sandy dolomite and limestone.
One of the largest sinkholes, Moses Hole, is located very close to the shore on Mariposa Point, and appears to be free from extensive historical influence. Although isolated from open bay waters, it clearly has been flushed by marine waters through a natural channel and later from two man-made channels dug as part of the state mosquito control effort.
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Tampa Bay is thought to have formed as the result of coalescing sinkholes. One core is located in the north central part of Hillsborough Bay (Fig. 1, Alafia River area) and overlies a small sinkhole in about 12 feet of water.
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