Ja. Holmes et al., A LATE QUATERNARY PALEOLIMNOLOGICAL RECORD FROM JAMAICA BASED ON TRACE-ELEMENT CHEMISTRY OF OSTRACOD SHELLS, Chemical geology, 124(1-2), 1995, pp. 143-160
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.