末次冰期以来南海北部物源及古环境变化的有机地球化学记录  

PROVENANCE AND PALEO-ENVIRONMENT CHANGES IN THE NORTHERN PART OF SOUTH CHINA SEA SINCE THE LAST GLACIAL PERIOD AS RECORDED BY ORGANIC GEOCHEMISTRY PROXIES

作　　者：周斌[1] 郑洪波[1] 杨文光[1] 李丽[1] 王慧[1] 

机构地区：[1]同济大学海洋地质国家重点实验室,上海200092

出　　处：《第四纪研究》2008年第3期407-413,共7页Quaternary Sciences

基　　金：国家重点基础研究发展规划项目(批准号:2007CB815906);国家自然科学基金创新研究群体科学基金项目(批准号:40621063);科技部"中荷科技联盟"项目(批准号:2004CB720506);中国博士后自然科学基金项目(批准号:20060400676)共同资助

摘　　要：摘要文章在AMS^14C定年的基础上建立了南海北部MD05—2905钻孔（20°08．17’N，117°21．61’E）末次冰期以来有机地球化学记录的时间序列，利用其中的正构烷烃、甾醇和烯酮等有机分子标志物对南海北坡25ka以来沉积物物源、气候环境变化进行探讨。长链正构烷烃总含量和浮游植物标志物总含量表明25．0～14．5kaB．P．时段南海北部沉积物中陆源物质输入、海洋初级生产力浮游植物输入均较高，14．5～8．5kaB．P．时段迅速降低，全新世8．5kaB．P．之后稳定在较低水平。末次冰期海平面低，陆架出露面积大，陆源物质搬运至沉积地点的距离短，强盛的冬季风及其驱动的洋流有利于大量的陆源物质搬运至该沉积地点；14．5kaB．P．，对应于MWPIa时期，陆源物质输入迅速减少，海洋初级生产力的迅速降低，印证了此时海平面的快速上升。C31／C17物源参数表明陆源物质输入和海洋内生源输入在25．0～14．5kaB．P．时段和14．5～8．5kaB．P．时段分别占据了主要地位，这表明海平面变化对陆源物质输入影响可能更大；全新世8．5ka之后，陆源、海洋内生源输入交替占据主要地位，这可能与东亚季风增强有关。从有机分子标志物研究来看，海平面的变化对陆源物质输入及总海洋初级生产力可能均有重要控制作用，但海洋初级生产力中某些藻类如硅藻可能受控于不同的气候因素。C28甾醇含量指示硅藻在MWPIa和MWPIb时期大量增多，这可能是14．5～8．5kaB．P．海洋内生源输入相对较多的重要原因，同时，对11．0～8．5kaB．P．时段的碳酸钙低值事件可能有一定贡献，但其对海陆环境的响应还有待于进一步研究。Organic matter in sediments is an interactive product of land and ocean, so its molecular assembled characteristics can reflect organic provenance and corresponding paleo-environmental changes. Based on AMS 14C age data, we established the organic geochemistry sequence of MD05 - 2905 core （ 20°08. 17＇ N, 117°21.61＇E ） , and we selected some indices of n-alkanes, sterols, and alkenone to recover the provenance and climatic and environmental changes in the northern part of South China Sea since the last 25ka. The results of long chain total n-alkane concentration and total phytoplankton biomarker concentration indicated that terrigenous matter and marine primary productivity were both high during 25.0 - 14.5kaB. P,and decreased rapidly during 14. 5- 8.5kaB. P., and remained low level after 8.5kaB. P. During the glacial period,the sea-level was low and the continental shelf outcrops largely,then the distance between terrigenous source and sedimentation site was shortened, causing more terrigenous material transported to depositional location. After about 14kaB. P.,which was coincident with Meltwater Pulse（MWP） Ia,the most rapid decrease of terrigenous input and marine primary productivity reflect a rapid retreat of the coastline in South China Sea at that time. C31/C17 index indicated that terrigenous input and marine endogenous origin takes primary position during 25.0 - 14. 5kaB. P. and during 14.5 - 8.5kaB. P. respectively, which reflected that sea level change may have taken more effects on terrigenous input. After 8.5kaB. P., terrigenous input and marine endogenous origin takes primary position alternatively,which maybe related with strong Asian Monsoon at that time. From our study,we speculated terrigenous input and total marine primary productivity are both controlled by sea level, but some certain marine primary such as diatom is controlled by other climate and environmental changes. C28 sterols increased during MWP Ia and MWP Ib, which is contributed to the primary position of the marine endog

关 键 词：南海北部 有机分子标记物 物源 海平面 古气候环境 

分 类 号：P736[天文地球—海洋地质]