全新世冲绳海槽北部陆源输入物变化及其古气候意义  

HOLOCENE TERRIGENOUS INPUT CHANGES IN THE NORTHERN OKINAWA TROUGH AND THEIR PALEOCLIMATIC IMPLICATIONS

作　　者：黄小慧[1] 王汝建[1] 翦知湣[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：《海洋地质与第四纪地质》2009年第5期73-82,共10页Marine Geology & Quaternary Geology

基　　金：国家重点基础研究发展规划项目(G2007CB815903);国家自然科学创新研究群体科学基金项目(40321603);同济大学国家大学生创新训练计划项目

摘　　要：运用多种方法,重建了全新世以来冲绳海槽北部地区陆源输入物以及火山碎屑物的沉积历史。在11.0～6.0kaBP期间,北部冲绳海槽的陆源物质供应量主要受控于海平面变化。由于该时期海平面上涨了50～60m,东海陆架上的海岸线快速后退,导致输入北部冲绳海槽的陆源碎屑物和有机质明显减少,沉积物粒度变细。在8.1～7.8kaBP期间,沉积物中的火山玻璃数目显著增加,导致该时段沉积物粒度急剧增大。经对比分析,该火山玻璃层即为源自日本南部Kikai火山的K-Ah火山灰层。但深海沉积序列中该火山灰层年龄比陆相记录中的7.3kaBP偏老几百年,推测这是由海洋14C测年的校正问题引起的。早全新世冲绳海槽地区的碳储库年龄应该比现在偏老300～500a,导致14C测年的校正值出现偏移。一些陆源烷烃的参数指标显示,全新世以来东亚地区草本植物不断增多,而木本植物逐步减少,表明陆地干旱化程度逐渐加强,这与全新世东亚夏季风减弱相对应。In the present study multi-approach has been employed to investigate the Holocene sedimentations of the river discharge and volcanic particles in the northern Okinawa Trough. During 11. 0-6. 0 kaBP,amounts of terrigenous particles and organic matter input to the northern Okinawa Trough as well as the particle grain sizes were found to have obviously decreased, which was a result from 50-60 m global sea level rise and a rapid retreat of coastline in the East China Sea. Thereby, the terrigenous input to the Okinawa Trough should be first orderly controlled by sea level changes in the early to middle Holocene. The volcanic glass shard concentration prominently increased during 8.1 - 7.8 kaBP, which was recognized as the K-Ah tephra derived from Kikai volcano in southern Japan. However, the K-Ah tephra age in the deep sea sediment sequence is much older than that of 7.3 kaBP in a variety of terrigenous records. This inconsistence was probably induced by the uncertainty of marine ^14C age calibration. Reservoir age of the northern Okinawa Trough in the early Holocene was considered to be 300-500 years older than that of the present. A set of proxy records based on the distribution of terrigenous alkane show an increasing expansion of the C4 plant in the East Asia continent during the Holocene, hinting the aridity was gradually enhanced in the inner part of China, which is consistent with the Holocene decrease in summer monsoon precipitation in this region.

关 键 词：陆源物质 火山灰 植被变化 东亚夏季风 全新世 冲绳海槽 

分 类 号：P736.21[天文地球—海洋地质]