南海北部末次冰消期及快速气候回返事件

对南海北部陆坡Ｖ３６－０６－３柱状样上部进行高分辨率地层学研究、浮游有孔虫和稳定同位素分析，并运用转换函数法和加权平均法求取约１５０００—７０００ａＢ．Ｐ．的末次冰消期中古环境参数的变化。结果发现约１０５００—７９００ａＢ．Ｐ．期间有一次强烈的古气候回返事件，与新仙女木期相对应，但持续时间较长。在此期间，冬季平均表层水温下降２．７℃，溶解氧与磷酸盐磷含量增高，古盐度与碳酸盐溶解度略有上升，黑潮水的影响大为降低，推测系海面上升过程中爪哇海海水进入南海所致。

THE LAST DEGLACIATION IN THE SOUTH CHINA SEA AND THE RAPID CLIMATE RETURN EVENT

Core V36-06-3(19°00.5' N, 116°05.6' E, water depth 2 809 m, length 12.15 m) from the northern continental slope of the South China Sea(SCS) has been systematically studied for paleoceanography. For a high resolution study of the last deglaciation history of the SCS, its uppermost part(0-161 cm) was resampled at 4-5 cm intervals and reanalysed. The downcore census data of planktonic foraminifera were interpreted for the winter and summer sea surface temperature(SST) using Transfer Function FP-12E, and also for salinity, oxygen and phosphate content, Foraminiferal Dissolution index and the variations in water masses. According to the oxygen isotope stratigraphy, the core interval between 101 cm and 51 cm corresponds to the last deglaciation(approximately 14 800-7 000 a B. P.) with a 1.23‰ decrease in δ18O. Over the last deglaciation the SST of SCS has increased by 5.70℃ for winter and 2.14℃ for summer(Fig. 1) and its surface water salinity increased by 1-2‰, but its dissolved oxygen content decreased by 0.83 ml/L and its phosphate concentration by 0.37 μg.atom/L(Fig. 3). Judging from the Core V36-06-3, the last deglaciation in the SCS has witnessed 2-3 short term climate return events, and the most significant one recorded in the core interval of 8056 cm has been dated by the oxygen isotope stratigraphy to 10 500-7 900 a B. P., roughly corresponding to the Younger Dryas event in age but lasting until the end of the termination. This abrupt event is characterized by a SST decrease of 2.7℃ for winter and 0.9℃ for summer(Fig. 1), an increase in oxygen content, phosphate concentration, salinity, carbonate dissolution(Fig. 3) and a remarkable reduction of the Kuroshio influence(Fig. 2). It is speculated that the gateway between the Java Sea and tile SCS(sill depth 36 m) was opened about 10 500a B. P. as a consequence of sea level rising, and the nflow of the Java Sea water has diminished the Kuroshio influence in the SCS. Although the above described event is still waiting for the result of its AMS-14C dating and similar analyses are needed for more cores in the area, its discovery in the northern SCS is undoubtedly of prominent significance. Despite of the opinion about the absence of the Younger Dryas in the SCS, the climate return event recorded in Core V36-06-3 together with the oxygen isotope record of the Younger Dryas in the neighbouring Sulu Sea has provided evidence for its occurrence in the low-latitudinal West Pacific and, hence, for its global nature.