18.5ka以来冲绳海槽中部沉积物碎屑态来源和古环境变化的常量元素记录  

PROVENANCE OF DETRITAL DEPOSITS AND PALEOENVIRONMENTAL CHANGES IN THE MIDDLE OKINAWA SINCE 18.5KA:EVIDENCE FROM MAJOR ELEMENTS

作　　者：蔡明江[1,2] 李铁刚[3,4] 于心科[1] 陈红瑾[1,2] 徐兆凯[1,4] CAI Mingjiang LI Tiegang YU Xinke CHEN Hongjin XU Zhaokai(Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China University of Chinese Academy of Sciences, Beijing 100049, China Key Laboratory of Marine Sedimentology and Environmental Geology, First Institute of Oceanography, SOA, Qingdao 266061,China Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266061, China)

机构地区：[1]中国科学院海洋研究所海洋地质与环境重点实验室,青岛266071 [2]中国科学院大学,北京100049 [3]国家海洋局第一海洋研究所海洋沉积与环境地质国家海洋局重点实验室,青岛266061 [4]青岛海洋科学与技术国家实验室海洋地质过程与环境功能实验室,青岛266061

出　　处：《海洋地质前沿》2017年第5期22-31,共10页Marine Geology Frontiers

基　　金：国家自然科学基金委员会-山东省人民政府海洋科学研究中心联合资助项目(U1606401);国家自然科学基金(41376064;41106043;41676038);国家海洋局全球变化与海气相互作用专项(GASI-GEOGE-06-02;GASI-GEOGE-02)

摘　　要：为进一步了解冲绳海槽中部18.5ka以来柱状沉积物碎屑态的常量元素组成特征及其古环境指示意义,对KX12-3孔进行了151个样品中碎屑态的提取及其常量元素和粒度综合分析。结果表明:主要常量元素含量表现出明显的两段式垂向变化特征,底部的Z1阶段(492~96cm)形成于末次冰消期及早全新世(18.5~9.6ka),中国大陆河流(长江、黄河)物质输入是沉积物中陆源碎屑物质的主要来源;而顶部的Z2阶段(96~0cm)则形成于早全新世以来(<9.6ka),沉积物中的陆源碎屑物质仍以中国大陆来源为主,台湾物质输入也有一定贡献。此外,岩心中还记录到了7.3ka时发生的K-Ah火山事件。常量元素相关性、R型因子及典型常量元素比值分析均表明主要氧化物含量在垂向上的变化主要受控于附近的陆源碎屑物质输入,热液活动和火山物质的影响较小。不同时期陆源碎屑物质对研究区的影响表现出明显的变化规律,并与海平面波动及黑潮的演化具有很好的耦合关系。此外,在5~3.5ka期间,KX12-3孔的Fe_2O_3、MgO、Fe/Ti、Mg/Ti值及粒度减小,这应该是由当时黑潮的减弱或"摆动"出冲绳海槽引起的。Major elements and grain sizes for 151 detrital samples collected from the core KX12-3 at the middle Okinawa Trough were studied for reconstruction of sediment provenance and paleoenvironment over the time of last 18.5 ka. Upon the variations in major element compositions, the core is divided to two distinct depositional units, Segment 1 （Z1;18.5-9.6 ka） and Segment 2 （Z2; 〈9. 6 ka）. De- posits of the Z1 （18.5-9.6 ka） are dominated by terrigenous detrital sediments from large Chinese riv- ers （e. g. the Changjiang and the Huanghe）. The detrital sediments of the Z2 have same provenances dominated by these Chinese rivers, but mixed with some fine-grained materials from Taiwan, which may have been transported to the study area by the Kuroshio Current. The K-Ah volcanic eruption happened at 7.3 ka is also recorded in the core. Integrated study of correlation analyses, R-type fac- tor, and major-element ratio show that the vertical change in major elements are mainly controlled by inputs of nearby terrestrial materials, whereas the contribution from hydrothermal activity and volcan- ism is little. In particular, the contribution of nearby terrestrial provenance shows an obvious trend which could be well correlated with the sea level fluctuation and the evolution of the Kuroshio Cur- rent. Furthermore, a prominent decline in Fe2O3、MgO、Fe/Ti.Mg/Ti values and finer grain size that occurred 5.0-3.5 ka may be linked to a suppression of the Kuroshio Current, or the shifting out of the current from the study area.

关 键 词：冲绳海槽中部 沉积物碎屑态 常量元素 海平面波动 黑潮 

分 类 号：P736.21[天文地球—海洋地质]