700年以来冲绳海槽南部黏土矿物来源及其对沉积环境的响应

本文对冲绳海槽南部HOBAB4-S2站700年以来的黏土矿物组成及结晶学特征进行了研究和分析，并对该区的物质来源以及黏土矿物所记录的东亚季风的演化历史进行了探讨。研究发现冲绳海槽南部HOBAB4-S2站黏土矿物组合总体是以伊利石（59%~77%，平均含量69%）和绿泥石（11%~17%，平均含量14%）为主，蒙脱石（5%~23%，平均含量12%）和高岭石含量（2%~6%，平均含量4%）则相对较低。通过黏土矿物研究对物源进行分析，发现冲绳海槽南部研究站位的黏土矿物中，伊利石、绿泥石以及高岭石主要来自于台湾岛上的河流，尤其是兰阳溪，蒙脱石则主要是来自于长江和东海大陆架的悬浮再沉积。蒙脱石/（伊利石+绿泥石）比值可以用来大致反映长江和东海大陆架与台湾岛对研究区物质输入的相对贡献。其相对贡献量的变化很好地记录了小冰期（1405 A.D.—1850 A.D.）东亚夏季风的减弱和台湾岛东北部-冲绳海槽南部地区相对湿润的气候特征。而该比值所指示的现代暖期（1960 A.D.）夏季风强度的减弱则可能主要是受到人类活动的影响。

Sediment provenance and its response to the paleoenvironment in the southern Okinawa Trough over the past 700 years

The clay mineral composition and crystallographic characteristics of core HOBAB4-S2 from the southern Okinawa Trough (SOT) over the past 700 years were studied and analyzed in this paper using x-ray diffraction. In addition, the sediment provenance and the history of the East Asian monsoon recorded by clay minerals in this area were discussed. It was found that the clay mineral assemblages in the SOT were mainly composed of illite (59%~77%, mean 69%), chlorite (11%~17%, mean 14%), minor smectite (5%~23%, mean 12%), and kaolinite contents (2%~6%, mean 4%). The provenance analysis of clay minerals showed that illite, chlorite, and kaolinite were mainly from rivers in Taiwan island, especially the Lanyang River, while smectite was mainly from the suspended re-deposition of the Yangtze River and the East China Sea shelf. The smectite/(illite + chlorite) ratio can be used to roughly reflect the relative contribution of the Yangtze River, East China Sea shelf, and Taiwan island to the sediment input of the SOT. The variation of its relative contribution reflects the weakening of the East Asian summer monsoon well during the Little Ice Age (1405 A.D.-1850 A.D.) and the relatively wet climate in the SOT-northeast Taiwan island. In contrast, the weakening of the summer wind intensity during the modern warm period (1960 A.D.) indicated by this ratio may have been mainly influenced by human activities.