PEAT RECORD FROM A HYPERSALINE COASTAL POND ON SOUTHERN ELEUTHERA ISLAND, BAHAMAS: IMPLICATIONS FOR SEA-LEVEL CHANGE AND LUCAYAN OCCUPATION

Peat accumulation in coastal lagoon settings has been linked on regional to global scales with climatic events and sea-level history. Coring transects were taken across Shad Pond, a shallow, constructional, hypersaline, coastal lagoon adjacent to Lighthouse Beach on the southern tip of Eleuthera Island, Bahamas. Three sites were cored down to bedrock, with penetration depths of 254, 114, and 104 cm. Two basal peat layers were collected from Site 1 (the most distal from the present barrier and the deepest portion of the lake) with a layer of gray, authigenic, carbonate clay between the two horizons. These peat layers yielded radiocarbon ages from ~5,000 cal yBP to ~3700 cal yBP. Peat was not present in any of the cores collected from two sites proximal to the welded barrier. The presence of peat indicates that sea-level rise may have affected the sedimentation in the pond. According to other sedimentary records from the Caribbean, there has been a strong correlation between peat building and sea-level rise during the Holocene (McKee et al, 2007). It is likely that at ~5000 cal yBP, Shad Pond was initiated as an open lagoon dominated by red mangrove (Rhizophora mangle), with black mangrove (Avicennia germinans) and buttonwood (Conocarpus erectus) present. It is likely that it was smaller and connected to the ocean before being separated by the emplacement of the fronting barrier complex. Furthermore, the presence of peat indicates that sea-level-mediated water table had to be stable long enough to allow for the development and spread of coastal mangroves and the accumulation of organic-rich sediment. Subsequently (~3700 yBP), a flux of sand from the seaward source buried the basal peat. As sea level rose, the pond broadened and expanded seaward. The peat may therefore provide a chronological constraint on mid-Holocene sea-level position on Eleuthera, with potentially additional implications for climatic shifts, storm intensity and Lucayan occupation in the northern Bahamian archipelago during middle Holocene.