MOLECULAR PALEOCLIMATOLOGY - RECONSTRUCTION OF CLIMATE VARIABILITIES IN THE LATE QUATERNARY

Lipid class compounds were studied in the deep-sea surface sediments f rom the central Pacific across a latitudinal transect at 175 degrees E (48 degrees N-15 degrees S) and a box core from the western tropical Pacific to discuss their utility as paleoclimatological indicators. Hi gher concentrations of C-25-C-35 n-alkanes were observed in the higher latitudes in the north Pacific. Their latitudinal distributions are s imilar to the spatial distributions of the observed soil dust concentr ations observed in the central-north Pacific atmosphere, suggesting th at the sedimentary C-25-C-35 n-alkanes are atmospherically transported from terrestrial higher plants, and can be used as an indicator of te rrestrial input to ocean environments. Downcore distributions of total C-25-C-35 n-alkanes suggest that terrestrial input doubled over the w estern tropical Pacific at the LGM and decreased by a factor of two at the last deglaciation period in comparison with the Holocene. The lat itudinal distributions of C-17-C-20 n-alkanes and pristane are higher in the high latitudes and equatorial region, probably reflecting the h igher primary productivity in surface waters of these oceans. The down core profiles of these compounds, as well as total organic carbon, lon g-chain alkenones and dinosterol suggest that biological production de creased significantly during the deglaciation period and slightly incr eased during the LGM compared with that of the Holocene. The downcore UK37 record suggests that the SST was almost constant over the last 20 000 y, which agrees well with the CLIMAP results and foraminifera del ta(18)O, although it disagrees with results from coral Sr/Ca ratios an d delta(18)O records. (C) 1997 Published by Elsevier Science Ltd.