A Pleistocene paleoceanographic record from the north slope of the SpratlyIslands, southern South China Sea

A 1.4 my paleoceanographic history for offshore north central Spratly Islan ds, southern South China Sea, is reconstructed using stable isotope, carbon ate content, coarse fraction, and planktonic foraminifera census data from gravity core SO95-17957-2. The chronological framework for 5095-17957-2 is based on stable oxygen isotope correlation with open ocean records and cons trained with AMS-C-14 dates, floral and faunal bioevents, and a Pleistocene microtektite event. Stable oxygen isotope composition of surface water ref lects mainly changes in high latitude ice volume but also riverine water in flux from surrounding land. Stable carbon isotope record suggests that surf ace water delta C-13 in the southern South China Sea has been modulated pri marily by global changes in atmospheric CO: since the early Pleistocene. Di ssimilarities between delta O-18 patterns in SO95-17957-2 and those in vari ous cores from the rest of the South China Sea indicate that between 60 and 120 Ka surface water chemistry at offshore north central Spratly Islands m ay be affected by different mechanisms. Those differences likely reflect un known hydrological conditions during stages 4 and 5. Carbonate content is l ower during the interglacial periods than during the glacial-deglacial peri ods, which are opposite to the general trend in the shallow South China Sea areas during the same period. Faunal composition, RSP and various dissolut ion indices suggest that productivity is the most important factor controll ing carbonate preservation. Dissolution above the lysocline may modify the productivity signal but cannot reverse the entire pattern. Faunal compositi on and carbonate Aux suggests productivity is higher during glacial-deglaci al than during interglacial. Stronger glacial winter monsoon induces strong er upwelling and deep mixing and enhances nutrient cycling in the surface o cean, which in turn increases productivity. Estimated summer sea surface te mperature (SST) based on transfer function Fe-12E agrees with delta O-18 an d is consistently between 28 and 29 degreesC during most of the last 1.4 my Winter SST reflects geographic location and changes in surface hydrology, and fluctuates between 25 and 28 degreesC, During the last glacial period d isconnection of the South China Sea from the Indian Ocean and the influx of temperate water through the Bashi Channel allowed winter SSTs to vary by a s much as 3.5 degreesC. Comparison of modem and estimated SST and SST estim ates based on different methods suggest that G. bulloides acid G. menardii are probably overweighed in transfer function FP-12E, which cause discrepan cies in SST estimation. (C) 2001 Elsevier Science B.V. All rights reserved.