冲绳海槽中部沉积物物质来源和沉积环境分析

本文基于AMS14C高精度测年，通过对柱状沉积物HOBAB2-S2的粒度、微量元素和稀土元素的分析，对冲绳海槽中部区5 300 a以来的物质来源和沉积环境进行了研究。通过对该孔的稀土元素与微量元素的研究发现研究区沉积物质具有陆源属性，并且通过不同物源区沉积物的稀土元素散点图表明5 300 a以来沉积物主要来自于台湾。文中将粒度特征作为研究区域沉积环境，尤其是水动力（黑潮）强弱的指示参数，根据粒度变化曲线，可将沉积过程分为4个阶段:第一阶段（5.30~3.81 ka BP），粒径由粗变细，黑潮强度逐渐减小；第二阶段（3.81~2.70 ka BP），粒径波动较大，无明显增大或减小趋势，表明沉积环境处于相对波动状态，水动力强弱不稳定；第三阶段（2.70~0.97 ka BP），粒径变化较小，表明沉积环境处于相对稳定状态，研究区的水动力条件较稳定；第四阶段（从0.97 ka BP至今），粒径逐渐变粗，水动力条件增强。

Analysis on sediment provenance and environmental changes in the middle Okinawa Trough

Based on the data of grain size and trace elements coupled with high-precise AMS¹⁴C dating, this paper dealed with the provenance and sediment environment evolution of the middle Okinawa Trough for the last 5 300 a with the sample from the Core HOBAB2-S2. The analysis on REE and trace elements showed their affinities to the terrigenous sediments in the study area. In combination with REE parameters of potential sediment sources, the sediments were mainly originated from Taiwan. The grain size was used to be the indicators of sediment environment, especially the vigor of local current(the current was mainly referred to Kuroshio Current in this paper). The conclusions were summarized as follows. Four periods were divided. During the first period(5.30-3.81 ka BP), grain size was getting finer, which indicated the Kuroshio Current weakened gradually. In the period of 3.18-2.70 ka BP, the garin size showed distinct change and we can deduce that the sediments suffered a relative volatility period. During the third period, from 2.70 ka BP to 0.97 ka BP, the environment was stable inferred from the grain size with little changes. Since 0.97 ka BP, the sediments grain size was larger than before and indicated the enhance of the strength of Kuroshio Current.