Sedimentary response to volcanic activity in the Okinawa Trough since the last deglaciation  

作　　者：蒋富清 李安春 李铁刚 

机构地区：[1]Key Laboratory of Marine Geology and Environment,Institute of Oceanology,Chinese Academy of Sciences

出　　处：《Chinese Journal of Oceanology and Limnology》2010年第1期171-182,共12页中国海洋湖沼学报（英文版）

基　　金：Supported by the Pilot Project of the National Knowledge Innovation Program of the Chinese Academy of Science (No. KZCX2-YW-221);the National Natural Science Foundation of China (No. 40506016,90411014 and 40976026);National Basic Research Program of China (No. 2007CB815903)

摘　　要：To investigate the relationship between volcanic activity and sediment record on regional and temporal scales,158 surface sediment samples were collected from the East China Sea Shelf to the northern Okinawa Trough (OT),and two cores recovered in the northern and southern OT,respectively.Mineralogy,grain-size,and geochemical analyses of those samples show that:1) volcanic glass,volcanic-type pyroxene,hypersthenes,and magnetite increase in sediment influenced by volcanic activity;2) sediment grain sizes (and also silt content) increase in ash layers;and 3) the contents of Na2O and Zr are higher,while terrigenous elements,e.g.,TFe2O3 and K2O,and biogenous compositions,e.g.,CaO and Sr,are relatively lower in ash layers than those of non-ash layers.The distribution of volcanic ash has three distinguishing characteristics:1) volcanic ash is more abundant in the northern and central OT than the southern OT;2) volcanic ash increases from continental shelf to the trough;3) the sediment during the last 12 000 a suggests stronger volcanic events than during 15 000-12 000 a.The eruptive locations,frequency,and volume of calderas are among the most important factors controlling the distributions of volcanic ash.In addition,the main Kuroshio warm current that extends northward probably impeded the diffusion of volcanic ash to the west and south in the OT.However,a southward current probably carried some volcanic ash toward southern OT.To investigate the relationship between volcanic activity and sediment record on regional and temporal scales, 158 surface sediment samples were collected from the East China Sea Shelf to the northern Okinawa Trough （OT）, and two cores recovered in the northern and southern OT, respectively. Mineralogy, grain-size, and geochemical analyses of those samples show that： 1） volcanic glass, volcanic-type pyroxene, hypersthenes, and magnetite increase in sediment influenced by volcanic activity; 2） sediment grain sizes （and also silt content） increase in ash layers; and 3） the contents of Na2O and Zr are higher, while terrigenous elements, e.g., TFe2O3 and K2O, and biogenous compositions, e.g., CaO and Sr, are relatively lower in ash layers than those of non-ash layers. The distribution of volcanic ash has three distinguishing characteristics： 1） volcanic ash is more abundant in the northern and central OT than the southern OT; 2） volcanic ash increases from continental shelf to the trough; 3） the sediment during the last 12 000 a suggests stronger volcanic events than during 15 000-12 000 a. The eruptive locations, frequency, and volume of calderas are among the most important factors controlling the distributions of volcanic ash. In addition, the main Kuroshio warm current that extends northward probably impeded the diffusion of volcanic ash to the west and south in the OT. However, a southward current probably carried some volcanic ash toward southern OT.

关 键 词：SEDIMENT ash layer last deglaciation Okinawa Trough 

分 类 号：P317[天文地球—固体地球物理学]