THE LONG-TERM UPLIFT HISTORY OF BARBADOS: IMPLICATIONS FOR COASTAL COMMUNITIES AND SEA LEVEL RECONSTRUCTIONS

The island of Barbados consists of uplifting coral reef terraces that document past sea-level fluctuations. With the acceleration of rising sea-level due to climate change, understanding the history and variable amounts of uplift rates around the island are vital for predicting future risks to coastal communities in Barbados and help refine our understanding of several key sea level highstands often used as future analogs. Absolute dating techniques used in previous studies of this location have focused primarily on the age of the lower elevation reef terraces (currently ~10 to 91 meters [m]) and only reconstructed uplift rates back to ~250 ka. However, numerous coral reef terraces can be found at higher elevations (up to ~270 m), which may provide more accurate long-term uplift rates around the island. Earlier studies utilizing U-He dating techniques have attempted to date a few of these intermediate terraces going back to ~700 ka, including just above and below a prominent scarp known as the Second High Cliff (~100-180 m), but these incorporate large age uncertainties. Until now, the uppermost terraces have never been geochemically dated. We use Sr isotope stratigraphy (SIS) and U-Th dating methods on in situ corals to date several of the higher elevation terraces. Using SIS on the uppermost coral terrace (~270 m), we were able to constrain the emergence of the island to a minimum of 1.1 Ma. In addition, SIS and U-Th dating on the same individual corals from the base of the Second High Cliff provides a direct comparison of the two dating methods. We establish the indicative range of paleo sea-level for each of the dated terraces using reef morphology, facies zonation, and stratigraphy from surveyed transects and combine these data with global estimates of paleo sea-level to obtain uplift rates on each of the individual terraces. Mapping and dating multiple upper terraces across the island will help document how stable long-term uplift rates are around Barbados and give insight into the threat of sea-level rise facing the island’s coastal communities.