24ka来冲绳海槽北部沉积物来源的高分辨率常量元素记录

PROVENANCE OF SEDIMENTS IN THE NORTHERN OKINAWA TROUGH OVER THE LAST 24 KA:HIGH RESOLUTION RECORD FROM MAJOR ELEMENTS

为进一步了解冲绳海槽北部24ka来柱状沉积物的常量元素组成特征及其物源和古环境指示意义,对PC-1孔进行了402个常量元素和粒度及344个浮游有孔虫氧同位素的综合分析,其平均样品分辨率高达百年时间尺度。结果表明:沉积物中的主要常量元素含量表现出明显的3段式垂向变化特征,并记录到了7.3和12.7cal.kaBP时的两次火山事件;物源判别图解及R型因子分析则揭示出主要氧化物含量在垂向上的变化主要受控于附近陆源物质输入,而热液活动和海洋生物沉积作用及火山物质的影响较小。特别是不同陆源物质对研究区的影响表现出明显的变化规律,与海平面波动及对马暖流形成演化间具有良好的耦合关系,但期间的典型古气候事件却并未明显改变沉积物中的陆源物质组成,从而为揭示24ka来冲绳海槽北部地区陆源物质输入演化历史,及其主要控制因素提供了新的高分辨率资料。

Major elements were studied for reconstruction of sediment provenance and paleoenvironment over the last 24 kaBP with the samples collected from Core PC-1 in the northern Okinawa Trough. In addition to major elements, grain size of 402 samples and planktonic foraminifer 3180 of 344 samples have been analyzed that leads to an average resolution at centennial scale. The study offers a new high resolution ma- terial for reconstructing the history and main control factors of the sediment input in the northern Okinawa Trough over the last 24 ka. In according to the variation in major element compositions, the core could be divided into three distinct depositional units, separated by two volcanic layers at 7.3 and 12.7 cal kaBP re- spectively. Both provenance discriminating plot and R-mode factor analysis indicate that vertical changes in major elements are mainly contributed by the nearby terrestrial materials, whereas the contribution from hydrothermal activity, marine biologic deposition, and volcanism are minor. In particular, the contribution of nearby terrestrial materials show an obvious change trend and can be well correlated with the sea level fluctuation and the evolution of the Tsushima Warm Current. It seems that paleoclimate renders no signifi- cant impact on the change in terrigenous sediment provenance.