T168 The Margins of Reefs and Carbonate Platforms

Thursday, 8 November 2001
8:00 AM - 12:00 PM

REEF EDIFICES ON THE FLORIDA PLATFORM; AN EMERGING COMPLEX DISTRIBUTION

Paper number: T168-2
Program: Technical Sessions
Time: 8:00 AM – 12:00 PM

Authors

Abstract

Although reefs, both modern and ancient, associated with the famous Florida Keys have been examined and enjoyed for decades by scientists and the general public, work within the past 15 years have revealed that the distribution and morphology of reefal structures are more extensive and complex than previously realized. Considering that only a small portion of these coral edifices has been drilled and dated yielding late Pleistocene and younger ages, we propose that reefs have played a significant role in the Quaternary evolution of the entire Florida Platform along both the rim and ramp components. Indeed, the east-to-west, rim-to-ramp transition along the south platform margin has probably migrated westward resulting from an interplay between reefal and sand shoal development during phases of multiple sea-level highstands.

Examples of Florida reefal complexity are numerous. (1) Multiple early Holocene reef ridges on the east coast shelf are now dead due to export of inimical highstand lagoonal waters across them. (2) Outlier reefs, dated as MIS 5a, seaward of the main Florida Keys reef tract are located upon an extensive 35-m-deep terrace of unknown lithology and age. (3) Large, circular, reefal banks supporting and surrounding the Dry Tortugas consist of 9 m of Holocene reef on top of older and thicker reefal lithologies. (4) Paleoshorelines now in 60 to 80 m of water depth support a luxuriant coral and coralline algal benthic community (Pulley’s Ridge). (5) Drowned, now coral-devoid reefal structures having 15 m relief lie in 30 m of water depth within a cooler, temperate water setting (Middle Grounds).

Ultimately, we propose to conduct drilling to reconstruct reefal development in response to changing climate, paleoceanography and sea level.