Sediment fabrics, oxygenation history, and circulation modes of Japan Sea during the Late Quaternary
Sediment fabrics, oxygenation history, and circulation modes of Japan Sea during the Late Quaternary
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DOI：
10.1016/j.palaeo.2006.11.021
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发表时间：
2007-04
期刊：
影响因子：
--
通讯作者：
Satoko Watanabe;R. Tada;K. Ikehara;K. Fujine;Y. Kido
中科院分区：
文献类型：
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作者：
Satoko Watanabe;R. Tada;K. Ikehara;K. Fujine;Y. Kido
日本海第四纪半远洋沉积物的特点是，受到严重生物扰动、缺乏有机物的浅色层和层状细密、富含有机物的深色层的厘米至分米尺度的交替。这些暗层和亮层可以在整个盆地的较深处相互关联，被认为反映了底层水氧合的变化。然而，造成各个暗层的沉积机制和氧气消耗的原因尚不完全清楚。已认识到沉积富含有机物的暗层的两种可能的设置。一种是分层海洋（如黑海），有限的垂直平流导致盆地深处处于常生条件。另一个是上升流区域（如阿拉伯海），其中氧气最低区通过营养物上升流和表面生产力的增强而加强。在这项研究中，通过从不同纬度和水深收集的三个岩心研究了过去 160ka 期间沉积在日本海的半远洋沉积物的结构。根据相应的底层水氧合水平，织物分为 4 类。根据每个暗层内沉积物结构类别的分布模式定义了五种暗层类型。在年代框架中比较浅层和深层暗层类型为五种不同的深水循环模式提供了证据。这些环流模式反映了上升流和密度分层的相对强度，似乎与全球海平面变化以及气候对通过对马海峡的水流入性质的影响有关。
The Quaternary hemipelagic sediments of the Japan Sea are characterized by centimeter-to decimeter-scale alternations of heavily bioturbated, organic-poor light layers and finely laminated, organic-rich dark layers. These dark and light layers, which can be correlated throughout the deeper part of the basin, are considered to reflect changes in bottom-water oxygenation. However, depositional mechanisms responsible for individual dark layers and causes of oxygen depletion are not fully understood. Two possible settings for deposition of organic-rich dark layers are recognized. One is a stratified ocean (like the Black Sea) where limited vertical advection results in euxinic conditions in the deeper parts of the basin. The other is an upwelling region (like the Arabian Sea) where the oxygen minimum zone is intensified by enhanced nutrient upwelling and surface productivity. In this study, fabrics of hemipelagic sediments deposited in the Japan Sea during the last 160 ka were studied in three cores collected from different latitudes and water depths. Fabrics were classified into 4 classes based on corresponding bottom-water oxygenation level. Five dark layer types were defined based on the distribution patterns of sediment fabric classes within each dark layer. Comparison of dark layer types at shallower and deeper sites in a chronologic framework provided evidence for five different modes of deep-water circulation. These circulation modes, which reflect relative intensities of upwelling and density stratification, appear to be related to global sea-level changes as well as climate impact on the nature of water influx through the Tsushima Strait.