USGS Papers Highlight Major Events in the Florida Keys During the Past 325,000 Years

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USGS Papers Highlight Major Events in the Florida Keys During the Past 325,000 Years

April 2004

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In two papers by U.S. Geological Survey (USGS) authors, the Geological Society of America Bulletin is publishing a comprehensive, regional-scale analysis of the shallow geologic framework of coral reefs in the Florida Keys National Marine Sanctuary. The analysis is a compilation and assimilation of new and existing data sets, acquired by USGS scientists and other workers since the 1960s, that allow fresh interpretations of geomorphic development on a windward, tectonically stable platform margin over the past 325 ka.

The first paper, published in July 2003, showcases updated, detailed color contour maps of the Pleistocene bedrock surface and the thickness of overlying Holocene accretions. The maps are the most extensive produced to date, encompassing approximately 2,130 km², or 25 percent, of the sanctuary. The map of the Pleistocene bedrock surface reveals the influence of an uneven, west-sloping topography on Holocene flooding history and coral-reef evolution. The map of Holocene accretions indicates that sediment is being transported off the lower-elevation area of the shelf.

The second paper, which will appear in the summer 2004 issue, provides a new, geomorphogenic approach to developing shelf-edge models by using seismic, core, aerial-photomosaic, and high-precision radiometric-age data correlated with eustatic sea-level maximums.

Together, the two papers provide a cohesive scientific database and overall perspective not previously available for the well-studied Florida Keys. Beyond their local relevance, the papers also represent a distinctive contribution to coral-reef-complex characterization in general, both at modern and ancient platform margins.

Key results with potential application to other reef-rimmed platform margins include:

influence of paleogeography, paleotopography, and physical environment;
replication of localized stratigraphic and shelf-edge symmetry and asymmetry perpetuated by repetitive transgressive processes;
development of upward, landward, and seaward reef-complex buildups;
manifestation of laterally alternating areas of shelf-margin progradation (during Holocene time in Florida, not previously formally documented) by infilling of discontinuous backreef troughs (of Pleistocene age in Florida); and
validation that not all windward margins fit the classic steeply inclined model.

The papers will be of interest to archeologists, climatologists, oceanographers, coral-reef scientists, carbonate geologists, geomorphologists, sedimentologists, stratigraphers, the hydrocarbon industry, government agencies, and academia. Beyond its scientific value, the information in these papers will be useful in local policy decisions, ranging from placing mooring buoys and offshore fixed navigation markers to implementing resource management and ecosystem restoration.

Full references for the two papers:

Lidz, B.H., Reich, C.D., and Shinn, E.A., 2003, Regional Quaternary submarine geomorphology in the Florida Keys: Geological Society of America Bulletin, v. 115, no. 7, p. 845-866 [URL http://sofia.usgs.gov/publications/papers/geomorph_keys/index.html].

Lidz, B.H., in press, Coral reef complexes at an atypical windward platform margin; late Quaternary, southeast Florida: Geological Society of America Bulletin, v. 116, no. 7-8.

Regional Quaternary submarine geomorphology in the Florida Keys
U.S. Geological Survey (USGS)

The Geological Society of America (GSA)
scientific society

USGS Coral Reef Studies
U.S. Geological Survey (USGS)

Center for Coastal and Watershed Studies
U.S. Geological Survey (USGS)

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April 2004

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cover story:
USGS Scientist Reviews NASA Mars Findings

Coral Reef Exhibit

USGS Assists in JASON Expedition

USGS Participates in Career Day

Geographic Information Systems Workshop

Ocean Research Conference

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April Publications List