T76 The Gulf of Mexico—Past, Present, and Future: Relating Ecology to Geology

Monday, 8 November 2004
8:00 AM - 12:00 PM

NEW GEOLOGIC THEMES EMERGNG FROM WEST FLORIDA OUTER SHELF STUDIES

Paper number: T76-7
Program: Technical Sessions
Time: 9:30 AM – 9:45 AM

Authors

Abstract

Geological and geophysical studies of the south and west Florida margin have progressed from regional seismic surveys and broad facies mapping to more focused, higher-resolution, digital examinations of specific sites of interest in recent years. These modern studies have focused on paleoshorelines and reefal structures that seem to be nearly ubiquitous along the distal portions of this carbonate ramp system. The application of new digital, high-resolution geoacoustic tools such 300 kHz multibeam, high-resolution seismic reflection and side-scan sonar profiling tied to meter-scale accuracy GPS navigation as well as high-definition bottom cameras mounted on improved, remotely operated vehicles have allowed us to significantly understand the roles of sea level, antecedent topography, substrate control, benthic biology and water -column properties from the late Pleistocene to Recent.

This technology has allowed us to address a number of broad themes in the past decade which include: (1) the widespread development of oolitic sediments during the Last Glacial Maximum (MIS 2) sea-level lowstand as seen in lithified, submerged paleoshorelines (-60-70 m) and upper slope bedforms (-110-175 m), (2) the discovery of MIS 5a reefs (-10 m) along the outer margin supported by a terrace of unknown age, (3) the rapid succession of sea-level fluctuations producing multiple, bathtub-ring-like shorelines on the upper slope, (4) lithified shorelines (barrier islands) providing the hard substrate required to support coral-reef development, (5) the rim-to-ramp transition , (6) plaeo-flow behavior of the Loop/Florida Current, and (7) the northern extent of relict reefal structures in waters today that cannot support reef growth. Finally, very recent seismic data have revealed extreme lowstand (~160 m) features that appear to be erosional scarps at some sites, but reefal buildups in others.

Drill core recovery and subsequent rock analysis are the next steps as they would provide the missing sea-level and paleoceanographic historical details.