Secular Variations in Provenance of Sedimentary Components in the Western North Pacific Ocean Constrained by Sr Isotopic Features of Deep‐Sea Sediments
Secular Variations in Provenance of Sedimentary Components in the Western North Pacific Ocean Constrained by Sr Isotopic Features of Deep‐Sea Sediments
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DOI：
10.1029/2021gc009729
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发表时间：
2022-01
期刊：
影响因子：
3.7
通讯作者：
E. Tanaka;K. Yasukawa;K. Nakamura;J. Ohta;T. Miyazaki;B. Vaglarov;S. Machida;K. Fujinaga;H. Iwamori;Y. Kato
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作者：
E. Tanaka;K. Yasukawa;K. Nakamura;J. Ohta;T. Miyazaki;B. Vaglarov;S. Machida;K. Fujinaga;H. Iwamori;Y. Kato
北太平洋西部南岛周围的深海沉积物记录了晚白垩世以来北太平洋中西部的沉积环境。前人对本区深海沉积物整体化学成分的研究表明，该沉积物柱可划分为5个化学地层单元，至少有3个夹层富含稀土元素。然而，端元成分及其丰度的变化表明组成的变化，以及影响它们的环境因素仍然不清楚。在这里，我们报道了从南岛周围的深海盆地采集的沉积物、海底锰结核和鱼牙的主体化学，包括最新分析的87Sr/86Sr比值，以确定沉积物的端员组分。结果表明，研究区远洋沉积物主要由陆源成分、含氢锰氧化物、生物钙磷酸盐和火山岩物质组成。锶同位素模拟和整体化学相结合显示，火山物质的输入增加了两次，可能是始新世末期至渐新世爆发火山活动的Izu-Bonin-Mariana热液，但在较早的事件中尚不清楚。陆源物质的来源已从北美转向东亚。南岛周围的块状沉积物化学地层学不仅可能是远洋领域局部环境变化的结果，也可能是太平洋周围的火山活动和太平洋板块运动导致的该地区向西北移动的结果。
Deep‐sea sediments around Minamitorishima Island in the western North Pacific Ocean record the depositional environment in the central to western North Pacific since the late Cretaceous. Previous studies on the bulk chemical composition of deep‐sea sediments in this area have revealed that the sediment column can be divided into five chemostratigraphic units with at least three intercalated layers enriched in rare‐earth elements. However, the end‐member components and their changes in abundance, which indicate compositional variation, as well as the environmental factors affecting them, remain unclear. Here, we report the bulk chemistry, including newly analyzed 87Sr/86Sr ratios of the sediments, seafloor Mn nodules, and fish teeth collected from the deep‐sea basin around Minamitorishima Island, to identify the end‐member components of the sediments. Our results suggest that the pelagic sediments in the study area are mainly composed of terrigenous components, hydrogenous Mn oxides, biogenic calcium phosphate, and volcanic materials. The combination of Sr isotope modeling and bulk chemistry revealed that the input of volcanic materials has increased twice, which might be Izu‐Bonin‐Mariana tephras of the latest Eocene to Oligocene explosive volcanism at the later event but is unclear at the earlier event. The provenance of terrigenous materials has changed from North America to East Asia. The bulk sediment chemostratigraphy around Minamitorishima Island could have resulted not only from the local environmental changes in the pelagic realm, but also from volcanism around the Pacific Ocean and the northwestward movement of the area due to the Pacific plate motion.