TIMING OF LATE HOLOCENE CORAL REEF DEVELOPMENT ON THE SOUTHEAST FLORIDA CONTINENTAL REEF TRACT

The relict Holocene reef system offshore southeast Florida documents the long-term development and response of South Florida’s coral reefs to a variety of environmental and climatic factors. Previous radiometric dating off Broward County, Florida suggests that active reef accretion terminated on the inner reef at ~5640 cal B.P. However, new evidence indicates that substantial reef growth reinitiated in the late Holocene at a relatively isolated area inshore of the relict reef tract on the Nearshore Ridge Complex (NRC). To constrain the timing of reef development at this location, we dated subfossil coral samples collected from three sites along the northern extent of the NRC off Broward County. A total of 14 samples from Acropora palmata, Pseudodiploria strigosa, Colpophyllia natans, and Orbicella annularis were dated using a combination of high-precision AMS radiocarbon and uranium-series dating techniques. Our results suggest that reef growth occurred between approximately 1885±90 and 3219±6 years B.P., partially corresponding to a period of high climatic variability in South Florida as well as the initial flooding of lithified beach ridges. Based on the timing and relatively short duration of reef growth in comparison to early and mid-Holocene reefs documented in this region, we interpret reef development at this site to have been restricted and broadly driven by an increase in shallow habitat area due to rising sea level. However, the specific environmental and climatic factors influencing reef initiation, growth, and termination remain elusive without further investigation. Nevertheless, these results provide a temporal context in which to characterize the paleoecological dynamics of late Holocene reef development on the southeast Florida continental reef tract.