Distribution and transport processes of lithogenic material from the Amur River revealed by the Sr and Nd isotope ratios of sediments from the Sea of Okhotsk
Distribution and transport processes of lithogenic material from the Amur River revealed by the Sr and Nd isotope ratios of sediments from the Sea of Okhotsk
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DOI：
10.1016/j.pocean.2014.04.015
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发表时间：
2014-08
影响因子：
4.1
通讯作者：
Tomoki Yasuda;Y. Asahara;Ryohko Ichikawa;T. Nakatsuka;H. Minami;S. Nagao
中科院分区：
文献类型：
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作者：
Tomoki Yasuda;Y. Asahara;Ryohko Ichikawa;T. Nakatsuka;H. Minami;S. Nagao
鄂霍次克海的初级生产力非常高，很可能是因为来自阿穆尔河的陆源输入，包括溶解物质和悬浮物。为了揭示鄂霍次克海西北陆架河流物质的搬运和沉积过程，对表层沉积物和悬浮物中碎屑的Sr和Nd同位素进行了研究。放射性成因同位素的区域差异表明，陆架碎屑主要有3个来源：阿穆尔河碎屑具有较高的87sr /86Sr比值（0.711 ~ 0.715）和较低的ε nd值（- 7.6 ~ - 7.3）；来自鄂霍次克海北部鄂霍次克-楚科奇火山带的火山碎屑，87sr /86Sr比值低（0.703），ε nd值高（+7 ~ +8）；库页岛北部沉积岩碎屑，87sr /86Sr比值高（0.709 ~ 0.710），ε nd值低（- 10.2 ~ - 9.2）。结果表明，阿穆尔河碎屑在西北大陆架上分散分布，并在流出大陆架的过程中沿库页岛东海岸向南运移。在库页岛东北海岸附近，来自库页岛北部地区的粗粒质碎屑仅分布在浅深度区的狭窄区域，未被搬运到陆架斜坡上。从陆架流出的阿穆尔河碎屑与鄂霍次克海中水（OSIW）从鄂霍次克海北部地区运来的鄂霍次克-楚科托卡火山物质混合在一起。以往的浊度研究支持了该区阿穆尔河碎屑的搬运过程，表明稠密的陆架水（DSW）携带西北大陆架上的重悬浮沉积颗粒并将其运送到OSIW。
Primary productivity is very high in the Sea of Okhotsk, most likely because of terrigenous input from the Amur River that includes dissolved matter and suspended matter. To reveal the transport and deposition processes of the fluvial materials in the northwestern continental shelf of the Sea of Okhotsk, the Sr and Nd isotopes of the detritus in the surface sediments and suspended matter were investigated. The regional variations of the radiogenic isotopes indicate that the detritus in the continental shelf has three main sources: Amur River detritus, with a high87Sr/86Sr ratio (0.711–0.715) and relatively lowεNdvalue (−7.6 to −7.3); volcanic detritus derived from the Okhotsk-Chukotka volcanic belt to the north of the Okhotsk Sea, with a low87Sr/86Sr ratio (0.703) and highεNdvalue (+7 to +8); and detritus from the sedimentary rocks north of Sakhalin Island, with a high87Sr/86Sr ratio (0.709–0.710) and lowεNdvalue (−10.2 to −9.2). The results indicate that the Amur River detritus is dispersed across the northwestern continental shelf and further transported southward along the east coast of Sakhalin while flowing out of the shelf. Around the northeast coast of Sakhalin Island, the coarse-grained detritus from the north region of Sakhalin Island is distributed only in the narrow region of the shallow depth area and is not transported to the shelf slope. The Amur River detritus flowing out of the shelf is mixed with the Okhotsk-Chukotoka volcanic material transported from the northern area of the Okhotsk Sea by the Okhotsk Sea intermediate water (OSIW). The transport processes of the Amur River detritus in this area are supported by previous studies of turbidity that indicated that the dense shelf water (DSW) entrains resuspended sedimentary particles on the northwestern continental shelf and transports them to the OSIW.