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Coastal & Marine Geology Program > Center for Coastal & Watershed Studies > Professional Paper 1751

Systematic Mapping of Bedrock and Habitats along the Florida Reef Tract—Central Key Largo to Halfmoon Shoal (Gulf of Mexico)

USGS Professional Paper 1751

by Barbara H. Lidz, Christopher D. Reich, and Eugene A. Shinn

Table of Contents
Project Overview
Project Objective
Geologic Setting
Primary Datasets
Primary Products - Overview Maps & Evolution Overview:
Bedrock Surface map.
Depth to Pleistocene Bedrock Surface
Reef & Sediment Thickness
Benthic Ecosystems & Environments
Sedimentary Grains in 1989
Summary Illustration Index Map
Evolution Overview
Tile-by-Tile Analysis
Satellite image of the Florida Keys showing location of tiles.
Organization of Report
Tiles: 1, 2, 3, 4,
5, 6, 7/8, 9/10,


This report would not have been possible without the able assistance of the late Captain Roy Gaensslen, who served as the charter-vessel captain for USGS studies from 1974 until his untimely death in August 1997. Far beyond his capabilities as a licensed sea-faring captain, his scientific interest and dedication encompassed all aspects of the marine realm. He conducted charters to the Bahamas, Caribbean, Central America, the Florida Keys, and the Gulf of Mexico for field trips and research. He was instrumental in the successful collection of many types of USGS data, ranging from documentary impacts on the seafloor environment of exploratory drilling by the oil-and-gas industry, to sampling of whitings (patches of milky water) actively forming on the Great Bahama Bank, to acquisition of seismic, sediment, core, water, and biological data that would advance scientific knowledge of geologic and modern history of coral reefs. In recognition and appreciation of the significance of Captain Roy's contributions to research in the Florida Keys National Marine Sanctuary, NOAA formally named a pristine patch reef in his honor in October 2003 and entered the name "Captain Roys Reef" (apostrophes are not used in geographic names) into the Nation's official geographic names repository (; see USGS/NOAA Underwater Memorial and Tribute to Captain Roy Gaensslen). The corals were still healthy when observed by E.A. Shinn in August 2004 but were less so in July 2007. However, fish were abundant.

Jim Pitts of the Florida Department of Transportation in Tallahassee kindly supplied the 1975 aerial photographs. Joan Rikon and Patricia Kibler of NOAA/National Geodetic Survey in Silver Spring, Maryland, provided the 1991 photographs. Both sets of photos were used to generate the benthic ecosystems and environments map. Gary W. Hill (USGS, retired) and Russell A. Ambroziak (USGS, National Mapping Division, Reston, Virginia) developed the software that allowed manual vectorization of raster images in the aerial photomosaics. The vector results comprise the benthic map. All photos used in this project were of highly significant scientific value, and in several instances they provided crucial information that would otherwise not have been known from any of the other datasets.

The senior author is especially grateful to Tonya D. Clayton (USGS), Robert B. Halley (USGS), and Brian Keller (Science Coordinator for the FKNMS) who painstakingly provided superior reviews that greatly strengthened this report. The following USGS employees helped draft various illustrations and put finishing touches on the digitized maps: Betsy Boynton, Amanda Frick, Laurinda Frye, Russell Peterson, Lance Thornton, and Robert Wertz. Russell Peterson performed the calculations and created the pie chart showing areal percentages of the benthic habitats mapped. Trent Faust and Jolene Shirley designed and created the project website and CD-ROM.

Funding for this project came from the U.S. Geological Survey Coastal and Marine Geology Program. The 1997 seismic geophysical dataset was acquired under Florida Keys National Marine Sanctuary Permit FKNMS-27-97. All products using any portion of the 1997 dataset are attributable to and should acknowledge that permit number. Previous individual marine sanctuaries now part of the FKNMS granted permits for various types of USGS research conducted in local areas of the reef tract in earlier years. Synthesized results of those studies and of studies performed by others are incorporated into and appropriately cited within this report.

Coastal & Marine Geology Program > Center for Coastal & Watershed Studies > Professional Paper 1751

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