南沙南部近30ka来的古海洋学记录

PALEO-OCEANOGRAPHIC RECORD OF THE PAST 30 Ka IN THE SOUTHERN NANSHA AREA,SOUTH CHINA SEA

南海南部 1796 2柱状样 (7°11′N、112°5′E,柱长 8m,水深 196 8m)中近 30 ka来的沉积物堆积速率计算结果显示 ,该孔冰期平均堆积速率为全新世的 3倍多。其变化与冰期时海平面下降、地表径流所携陆源物质增多、全新世时海平面的回升以及陆源物质的提前卸载有关。浮游有孔虫氧同位素测定结果表明 ,该孔的浮游有孔虫的氧同位素冰期 /全新世差值高于南海的平均值 ,更大于开放性大洋赤道西太平洋低纬度区的平均值。Ca CO3变化则受陆源物质的“稀释作用”控制 ,而溶解作用对其影响并不太显著。

The accumulation rates of the past 30 ka were calculated for core 17962(112°5′E,7°11′N,core length 8 m,water depth 1968 m).Its average rate in the glacial time is 2 times higher than that in the Holocene,and mainly controlled by the changes of terrestrial influx.During the glacial sea level drop,a vast amount of terrestrial materials transported by rivers have been deposited on the upper continental slope,causing a high accumulation rate.With the sea level rising in the Holocene,most of terrestrial materials loaded on the extensive Sunda shelf,resulting in a marked decrease in the accumulation rate on the slope.Moreover,the dilution of terrestrial material,not the dissolution,is responsible for the CaCO 3 fluctuation observed in this core.The glacial Holocene planktonic foraminifer δ 18 O difference calculated from core 17962 is higher than its average value of the South China Sea,and much higher than that of the low latitudinal western Pacific.