A LATE QUATERNARY PALEOLIMNOLOGICAL RECORD FROM JAMAICA BASED ON TRACE-ELEMENT CHEMISTRY OF OSTRACOD SHELLS

The trace-element chemistry of ostracod shells provides one of the mos t promising methods for palaeolimnological reconstruction. In this pap er, molar Sr/Ca and Mg/Ca ratios in shells of the ostracod Cypretta br evisaepta Furtos, 1934 were used to reconstruct the late Quaternary pa laeolimnology of Wallywash Great Pond, a small freshwater coastal lake in Jamaica, Analyses of modern Jamaican ostracods were undertaken to establish molar distribution coefficients (K-D(M)'s) for this species (K-D(Sr) = 0.306 +/- 0.069; K-D(Mg) = 0.0142 +/- 0.0088). These values were used to reconstruct past levels of (Sr/Ca)(water) and (Mg/Ca)(wa ter) for a 9.23-m lake-sediment core from Wallywash Great Pond. The re sults were coupled with previously-published stable-isotope (delta(18) O and delta(13)C) determinations on fine-grained calcite, to reconstru ct the salinity, palaeohydrology and palaeo-productivity of the lake o ver the last 125 ka B.P. (10(3) calendar years before present). Three major highstands with slightly elevated salinity occurred during marin e isotope stage 5, under elevated sea level and a humid climate. The l ake dried out similar to 93.5 ka B.P. as sea level fell and the climat e became drier. It refilled around 10.7 ka B.P. Three separate highsta nds during the Holocene were sustained by humid conditions and high re lative sea level. Although there were small increases in salinity duri ng the Holocene when sea level was close to the deepest part of the la ke, significant saltwater intrusion appears to have been prevented by freshwater discharge from inland, Throughout the late Quaternary, the salinity of the Great Pond showed low absolute variations, from simila r to 0.3 to similar to 0.6 parts per thousand. The long-term trends in lake level reflect both orbitally-induced changes in insolation and e ustatic sea level. Water-level fluctuations during the Holocene, howev er, reflect climatic changes on the millennial timescale rather than o rbital forcing or sea-level change.