Faunal and geochemical evidence for changes in intermediate water temperature and salinity in the western Coral Sea (northeast Australia) during the late quaternary

Ostracod assemblages and geochemical analyses of valves of specific ostracod taxa are used to reconstruct, both qualitatively and quantitatively, bottom-water temperatures (BWT) for the last 100,000 years in the western Coral Sea. The investigated core (51GC21) is situated in the lower reaches of the Antarctic Intermediate Water, at 1630 m water depth. First, we ran a Principal Coordinate Analysis (PCoA) of 42 surface samples from the Coral Sea, and then compared fossil assemblages with results of the PCoA. In addition, we selected well preserved specimens of the two genera Krithe and Bythocypris for Mg/Ca analyses. The Mg/Ca is used to infer past changes in BWT for intermediate waters of the western Coral Sea; results indicate large temperature fluctuations over the last 100,000 years. Of interest is the documentation that the BWT was similar to the present-day temperature during part of Isotope Stage 3. Comparison between our temperature record and the benthic foraminifer delta(18)O record of core 51GC21, and with the delta(18)O variations in seawater, as reconstructed by Labeyrie et al. (1987), allowed assessment of past changes in BWT salinity and density. Thus, we identify for the western Coral Sea three distinct periods on the basis of water mass density changes (i.e. for Isotope Stage 1, Stages 2, 3 and 4, and Stage 5). Our temperature record also indicates a good correlation with the 60 degrees S summer insolation calculations for the period between 25,000 yr B.P. and 75,000 yr B.P. Comparison of our results from this study with other records from the western Pacific (the Ontong Java Plateau in particular) reveal the role of New Guinea as an oceanographic barrier. A wet phase recorded on continental Australia coincides with our high bottom-water temperature record for isotopic Stage 3. (C) 1997 Elsevier Science B.V.