Early Holocene sea-level record from submerged fossil reefs on the southeast Florida margin

Massive fossil (outlier) reefs are preserved seaward of the modern shelf and reef tract along the southeast Florida margin. Thermal ionization mass-spectrometric (TIMS) U-Th dating of 16 pristine Acropora palmata and head corals cored from two transects document early Holocene reef growth from 8.9 to 5.0 ka, from approximately -13.5 to -7 m MSL (mean 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 reef 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 ka, attributed to West Antarctic Ice Sheet instability and changes in marine ice extent between 8 and 7 ka. Continuous in situ shallow-water reef growth in Florida during 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 records for Florida and the Caribbean are thus more likely to be artifacts of limited sampling and/or core coverage, and not necessarily a result of drowning.