| Summary: | Oxygen and carbon isotopic analyses have been carried out on calcareous nannofossils from ODP Site 1143 in the southern South China Sea. The results demonstrate that the 5180 values of calcareous nannofossils for the past 1 Ma vary systematically with those of planktonic and benthic foraminifera from the same site. But the average delta(18)O value of nannofossils is 1.869parts per thousand higher than that of planktonic foraminifera, and is 3.855parts per thousand lower than that of benthic foarminifera. There are systematic differences between the delta(13)C values of nannofossils, planktonic foarminifera and benthic foraminifera. The average delta(13)C of nannofossils is 0.756parts per thousand higher than that of benthic foraminifera, and is 0.460parts per thousand lower than that of planktonic foraminifera. The delta(13)C values of nannofossils exhibit a significant positive shift beginning near Isotope stage 14 and lasting until stage 8. This study also finds that there is a close ralationship between the delta(13)C of nannofossils and the percentage of Florisphaera profunda. This implies that the delta(13)C of nannofossils can be used as an indicator of sea water surface paleoproductivity.
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