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Home | Tampa Bay Study | Data | Task 3: History and Prehistory > Seismic Reflection Profiling

This page is archived and is no longer being maintained. Content was last updated in 2015. For current research, visit http://coastal.er.usgs.gov/.
Tampa Bay Study > Data > Task 3: History and Prehistory > Seismic Reflection Profiling

Location of all seismic data and boreholes used in this study.

Location of all seismic data and boreholes used in this study. (Larger)
Project Lead: Beau Suthard, College of Marine Science, USF

Seismic reflection data was collected throughout Tampa Bay to better understand paleodepositional environments through seismic facies analysis. To collect these data, the University of South Florida research vessel Price towed a seismic sound source and hydrophone array along predetermine survey tracklines.  The seismic sound source, known as an electrodynamic boomer, emits a loud sound pulse, generating sound waves that penetrate the seafloor.  As the sound waves travel deeper into the seafloor, they encounter different geologic layers which reflect back a portion of the sound energy to the hydrophone array.  Based on the travel time between the sound source, geologic reflector, and back to the hydrophone, the subsurface location of that geologic unit can be mapped.  The reflected sound wave data is collected and processed using specialized software that generates seismic profiles (two-dimensional graphic representations of the subsurface geology) (see images below) . The relationships of the geologic units shown in the seismic profiles are then interpreted in order to identify seismic sequences (related packages of stratigraphy). Where possible, the seismic sequences are correlated to known core borings in order to goundtruth the seismic data.  The University of South Florida worked in collaboration with the U.S. Geological Survey in order to collect and interpret seismic data for Tampa Bay.

The results of the seismic reflection survey indicate that the subsurface Tampa Bay basin was formed somewhere between 14 and 11 million years ago.  The basin is not the result of paleofluvial activity (ancient rivers) as are similar estuaries, but rather due to deep-seated collapse of the underlying limestone, resulting in a shallow surficial basin. This shallow basin is comprised of three geologically distinct regions: the Lower Tampa Bay Basin, a broad, deep basin located in Lower Tampa Bay; the Mid-Bay Trough, a deep, east-west oriented, restricted basin in north-central Tampa Bay (just south of the Inter-Bay Peninsula and Hillsborough Bay); and a broad bedrock high in central Tampa Bay that separates the two basins.

These basins have been filled by nine (9) distinct sedimentary sequences that originated from multiple sea-level events over the past several million years. When sea-level was low, rivers would flow further offshore, resulting in erosion for the Tampa Bay area and/or lakes in topographic low spots. When sea level was high, rivers provided sediment input to a small bay or shallow sea where modern Tampa Bay is now, resulting in sediment deposition [ Infill Cross Section ].  In addition, based on the seismic facies, it is clear that different depositional systems were active during these different sea-level events.  Four phases of sedimentary deposition were identified as part of this study [ Infill Map View ].  Phase 1 and Phase 2 deposition resulted from sea-level highstands, with Phase 1 sediments resulting from fluvial deposition from the south in both main basins while phase 2 was the result of fluvial deposition in the Lower Tampa Bay Basin that came in from the east.  Phase 3 deposition was also the result of a sea-level highstand, but was open-marine in origin, as opposed to the Phase 1 and 2 fluvial deposits.  Finally, Phase 4 is indicative of a sea-level lowstand, with the formation of a freshwater lake in the Mid-Bay Trough.

Top image: Uninterpreted seismic line.  Bottom image: Seismic line with interpretations.

Left image: Key to the five sequences as described in the seismic interpretations. Top image: Uninterpreted seismic line. Bottom image: Seismic line with interpretations. Red lettering refers to the sequences and green lettering refers to the sequence boundaries. There are five sequences in this interpretation, which was located in Lower Tampa Bay near the mouth to the Gulf of Mexico. These sequences and others are described in detail in Suthard 2005. (View images: Larger, Largest)


THESIS AND PUBLICATIONS:
This research is presented in more detail in the following M.S. Thesis and publications:

Hine, A.C., Suthard, B.C., Locker, S.D., Cunningham, K.J., Duncan D.S., Evans, M., and Morton, R.A., (2007). Karst Subbasins and Their Relation to the Transport of Tertiary Siliciclastic Sediments on the Florida Platform, in Swart, P.K. and Eberli, G.P., eds. IAS Special Publication in Honor of Robert Ginsburg.

Suthard, B.C., 2005. A Siliciclastic-Filled Sedimentary Basin in a Mid-Carbonate Platform Setting, Tampa Bay, Florida (unpublished M.S. thesis). University of South Florida, FL, USA, 79 pp.

Suthard, B.C., Hine, A.C., Locker, S.D., Duncan, D.S., Morton, R.A., Hansen, M.E., and Edgar, N.T., 2002. A Siliciclastic-Infilled Sedimentary Basin Within a Large Carbonate Platform, Tampa Bay, Florida. Eos Trans. AGU, 83 (47), Fall Meet. Suppl., Abstract OS61A-0210.

DATA SETS:

Beau Suthard (University of South Florida) and Kate Ciembronowicz (USGS) prepare the seismic sled for deployment in Tampa Bay.

Beau Suthard (University of South Florida) and Kate Ciembronowicz (USGS) prepare the seismic sled for deployment in Tampa Bay. The sled collects seismic reflection data that can be interpreted to determine the subsurface geology of Tampa Bay. (Larger)

Location of seismic surveys for 2001-2003 and 1989-1990 in Tampa Bay, Florida. (metadata)

These data sets are in ArcGIS Shapefile format. To view these files, you must have ESRI ArcGIS Software or other GIS software. A freely available lightweight version of ESRI's software is ArcGIS Explorer.


RELATED PRODUCTS:
Pictures from Seismic field surveys


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