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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

Introduction: Table of Contents Project Overview Project Objective Geologic Setting Primary Datasets Primary Products - Overview Maps & Evolution Overview: Introduction 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 Organization of Report Tiles: 1, 2, 3, 4, 5, 6, 7/8, 9/10, 11 Summary Acknowledg- ments References Disclaimer Related Publications

Primary Products Introduction Overview Map—Depth to Pleistocene Bedrock Surface Overview Map—Reef and Sediment Thickness Overview Map—Benthic Ecosystems and Environments Overview Map—Sedimentary Grains in 1989 Overview Map—Summary Illustration Index Map Evolution Overview—Coral Ages and Shelf-Edge Models Introduction: Primary products of this project are twofold: descriptive and interpretive digitized maps that provide regional geologic, biologic, and sedimentologic baseline datasets for that part of the Florida Keys National Marine Sanctuary that extends from central Key Largo to Halfmoon Shoal in the Gulf of Mexico (Fig. 6C), and innovative cross-sectional shelf-edge models for four selected areas, based on seismic-reflection contours and coral dates correlated with globally recognized periods of sea-level highstands. High-precision dating of corals indicates that seven coral reef ecosystems developed successively along the reef tract over a period of 325 ka. The four data-based overview maps are presented here. A fifth, an index map (Summary Illustration), is used to summarize and show locations of the oldest dates on corals, calcrete, and mangrove peat for the seventh reef system, the one that we see today. The shelf-edge models were derived using a combination of methods that address the origin, timing, evolution, and changes in surface landforms as the successive coral reef systems built the shelf upward and seaward. The four models are shown and described in Tiles 1, 6, and 7/8 in the tile-by-tile analysis. The models indicate that the seven successive coral reef ecosystems repetitively built the shelf margin through two coral reef architectures: a broad reef-and-trough architecture and a narrow ridge-and-swale architecture. continue to: Overview Map—Depth to Pleistocene Bedrock Surface

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