末次盛冰期末期以来南海北部陆坡的陆源物质输入及其控制因素

TERRIGENOUS INPUT TO THE NORTHERN SLOPE OF THE SOUTH CHINA SEA AND ITS CONTROLLING FACTOR SINCE THE LAST PHASE OF THE LAST GLACIAL MAXIMUM

通过对南海北部陆坡KNG5孔沉积物粒度、粘土矿物和14C年龄的综合分析,探讨了南海北部陆坡的沉积物来源及其控制因素。物源分析表明,KNG5孔17.5—12.5ka BP的沉积物主要来源于珠江,12.5ka BP时粘土矿物组合突然发生改变,并且自12.5ka BP以后,高岭石含量总体稳定,说明12.5ka BP时海平面已上升到相当的高度,并且可能当时南海的现代环流系统已开始形成,西行的广东沿岸流导致向外扩散的珠江物质减少,由于受北太平洋深层水(NPDW)和黑潮(KC)南海分支的作用,台湾成为此时沉积物的主要贡献者。KNG5孔17.5—11ka BP时期的粘土矿物和粒度变化主要受控于海平面和洋流系统的变化。全新世早期(11.0—8ka BP)平均粒径达到最细和1—2.2 m粒级含量达到最高值可能是强盛的夏季风作用的结果。全新世中晚期(8—0ka BP)1—2.2 m组分含量的减少是8ka BP以来东亚夏季风减弱的具体体现,1—2.2 m粒级含量指示的东亚夏季风变化能和北半球其它季风指标能很好地对应起来,说明这次季风减弱是北半球各个季风系统的共同现象。

AMS14C, dating grain size and clay minerals of Core KNG5 sediments taken from the northern slope of the South China Sea were analyzed to discuss the evolution of provenances and controlling factors since 18ka. Sediment source studies indicate that the sediment source of Core KNG5 was mainly from the Zhujiang （Pearl） River during 17.5—12.5ka BP, while the clay assemblages sudden change at 12.5ka BP indicated that the sea level had risen to a considerable height, the modern circulation system of South China Sea had begun to form, and the Guangdong Coast Current should have been the main contributor to the kaolinite spatial distribution prograding southward once entering the shelf. The main contributor was later changed ti Taiwan Island during 17.5—12.5ka BP owing to the influence of the North Pacific Deep Water （NPDW） and South China Sea Branch of Kuroshio. Grain size and clay minerals of Core KNG5 during 17.5—11ka BP were controlled by sea level change. The strong East Asian Summer Monsoon might be responsible for the minimum of mean grain size and the maximum contents of fluvial mud （1—2.2μm） in the Early Holocene. The decrease of fluvial mud （1—2.2μm） in the Middle and Late Holocene （8ka BP—0ka BP） well reflected the weak of East Asian Summer Monsoon since 8ka BP; and the content of fluvial mud （1—2.2μm） showed the evolution of East Asian Summer Monsoon, which corresponded well with other indexes of the Northern Hemisphere monsoon, showing that the weakened monsoon was the common phenomenon in each monsoon system of the Northern Hemisphere and also the monsoon evolution since Holocene in the global scale.