EARLY HOLOCENE SEA-LEVEL RECORD FROM SUBMERGED FOSSIL REEFS ON THE SOUTHEAST FLORIDA MARGIN

Massive fossil (outlier) reefs are preserved seaward of the modern she lf and reef tract along the southeast Florida margin. Thermal ionizati on mass-spectrometric (TIMS) U-Th dating of 16 pristine Acropora palma ta and head corals cored from two transects document early Holocene re ef growth from 8.9 to 5.0 ka, from approximately -13.5 to -7 m MSL (me an sea level). These samples fill a gap in the Florida Keys sea-level database and clarify the timing of a significant decrease in the rate of sea-level rise. A portion of this interval, represented by a gap in the Caribbean record of A. palmata reefs, has been interpreted as ree f drowning during an inferred catastrophic sea-level rise event of >45 mm/yr, or a 6.5 m rise between 7.6 and 7.2 ha, attributed to West Ant arctic Ice Sheet instability and changes in marine ice extent between 8 and 7 ka. Continuous in situ shallow-water reef growth in Florida du ring this interval precludes the occurrence of exceedingly rapid rates of sea-level rise and is consistent with the North Atlantic record of deglaciation from 9 to 7 ka. Gaps in the early Holocene sea-level rec ords for Florida and the Caribbean are thus more likely to be artifact s of limited sampling and/or core coverage, and not necessarily a resu lt of drowning.