FISC - St. Petersburg
Overview MapSummary Illustration Index Map: A Summary Illustration index map shows core components of what is known as the South Florida Ecosystem (e.g., McPherson and Halley, 1996; Causey, 2002): the Everglades, Florida and Biscayne Bays, the Florida Keys, and the reef tract, which lies just inside the 30-m depth contour that marks the shelf margin. These core components are linked geologically and hydrologically through porous limestone bedrock and a natural southward flow of ground and surface water. The core components are also linked biologically in that juvenile stages of various marine organisms inhabit different subenvironments within the ecosystem (Ley and McIvor, 2002; Cocheret de la Morinière et al., 2003; Serafy et al., 2003). An excellent sourcebook on past and present status of the many factors, both natural and anthropogenic, that comprise and affect the South Florida Ecosystem is found in Porter and Porter (2002).
The index map shows the locations and oldest radioisotope ages for Holocene materials dated along the reef tract. The ages have not been corrected for variations in production of the carbon-14 (14C) isotope used to date the materials and are given as abbreviated conventional radiocarbon ages (CRA). Coral ages indicate growth began first in the southwest and later in the northeast, which is consistent with lower bedrock elevation and earlier flooding of the southwestern part of the shelf.
From north to south, the Florida Keys vary in both orientation and rock composition (e.g., Hoffmeister and Multer, 1968). The upper and middle Keys parallel the margin and consist of the Key Largo Limestone (coral reef). The lower Keys, oriented nearly perpendicular to the margin, consist of the Miami Limestone (oolite).
The inset on the index map shows the location of Fort Lauderdale, where tiered barrier reefs developed offshore ~7 to 6 ka (Lighty et al., 1978, 1982), and the city of Orlando, once the northern boundary of the Everglades watershed (shaded area). The Everglades today is less than half this earlier size (Douglas, 1947).