末次冰期以来巽他陆架的演变及其对南沙群岛海区古环境的影响

EVOLUTION OF SUNDA SHELF SINCE LAST GLACIALAND ITS INFLUENCE ON PALEOENVIRONMENTCHANGES OF NANSHA ISLANDS SEA AREA

通过对南沙群岛海区 NS94－93柱样磁组构、矿物成分分析，结合14C测年，分析了末次冰盛期巽他陆架出露成陆及其后巽他陆架被海水淹没后南沙群岛海区沉积环境的变化，认为巽他陆架在 13．2ka B．P．时开始被海水淹没，约经历 600a左右趋于稳定；在末次冰期，南沙群岛海区水体封闭，沉积物以陆源物质为主，碳酸盐含量低 ；13.2—10ka B．P，沉积物以陆源物质为主，碳酸盐含量逐渐增加；至 10ka B．P，南沙群岛海区进人全新世，水体交换条件得到较大改善，沉积物中生源物质显著上升，陆源物质明显减少，碳酸盐含量一直维持在较高水平。

Based on data of X ray diffraction analysis, magnetic fabric measurements andradio carbon ages of core NS94--93 from Nansha Islands Sea Area, southern South ChinaSea, paleoenvironment changes were comprehanded when Sunda Shelf became land inlast glacial and afterward drowned by sea water. Sunda Shelf was drowned graduallysince 13. 2ka B. P., after about 600a, it was completely drowned by sea water and be-came stable. In last glacial,Nansha Waters became closer, sediments were dominated byterrigenous matters with low content of carbonate; l3. 2--10ka B. P., carbonate sedi-mentation was increased slowly; The boundary of Holocene and Pleistocene in NanshaIslands Sea Area is 10ka B. P., and from 10ka B. P. to present, water exchange of Nan-sha Waters was enhanced, the terrlgenous matters were decreased intensively in sedi-ments and the content of carbonate was very high.