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Sediments and sedimentary processes

机译：沉积物和沉积过程

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A giant mass-transport complex was recently discovered in the eastern Arabian Sea, exceeding in volume all but one other known complex on passive margins worldwide. The complex, named the Nataraja Slide, was drilled by International Ocean Discovery Program (IODP) Expedition 355 in two locations where it is ～300 m (Site U1456) and ～200 m thick (Site U1457). The top of this mass-transport complex is defined by the presence of both reworked microfossil assemblages and deformation structures, such as folding and faulting. The deposit consists of two main phases of mass wasting, each consisting of smaller pulses, with generally fining-upward cycles, all emplaced just prior to 10.8 Ma based on biostratigraphy. The base of the deposit at each site is composed largely of matrix-supported carbonate breccia that is interpreted as the product of debris-flows. In the first phase, these breccias alternate with wellsorted calcarenites deposited from a high-energy current, coherent limestone blocks that are derived directly from the Indian continental margin, and a few clastic mudstone beds. In the second phase, at the top of the deposit, muddy turbidites dominate and become increasingly more siliciclastic. At Site U1456, where both phases are seen, a 20-m section of hemipelagic mudstone is present, overlain by a ～40-m-thick section of calcarenite and slumped interbedded mud and siltstone. Bulk sediment geochemistry, heavy-mineral analysis, clay mineralogy, isotope geochemistry, and detrital zircon U-Pb ages constrain the provenance of the clastic, muddy material to being reworked, Indus-derived sediment, with input from western Indian rivers (e.g., Narmada and Tapti rivers), and some material from the Deccan Traps. The carbonate blocks found within the breccias are shallow-water limestones from the outer western Indian continental shelf, which was oversteepened from enhanced clastic sediment delivery during the mid-Miocene. The final emplacement of the material was likely related to seismicity as there are modern intraplate earthquakes close to the source of the slide. Although we hypothesize that this area is at low risk for future mass wasting events, it should be noted that other oversteepened continental margins around the world could be at risk for mass failure as large as the Nataraja Slide.
机译：最近在东部阿拉伯海中发现了一个巨大的大规模运输综合体，超过了全球被动边缘的其他已知复杂的储存。该复杂名为Nataraja Slide，由国际海洋发现计划（IODP）探险355在两个地点钻，其中〜300米（网站U1456）和〜200米厚（网站U1457）。该质量传输复合物的顶部由具有可重整的微基团组合和变形结构的存在，例如折叠和断层来定义。沉积物由两种大规模浪费的主要阶段组成，每个主要脉冲由较小的脉冲组成，通常翅片向上循环，均仅在基于生物数据上的10.8 mA之前施加。每个部位的沉积物碱基主要由基质支持的碳酸盐Breccia组成，被解释为碎片流动的产物。在第一阶段，这些Breccias与井下的钙化替补沉积在沉积的高能量电流，连贯的石灰岩块中，这些块块直接从印度大陆边缘和几张碎片泥岩床中源。在第二阶段，在沉积物的顶部，浑浊的浊度占主导地位，变得越来越多的硅质硅。在Site U1456，看到两个阶段都被看来，存在20米的血管泥岩部分，俯瞰〜40米厚的钙化型和坍塌的泥土和硅铁晶。散装沉积物地球化学，重型矿物质分析，粘土矿物学，同位素地球化学和碎屑锆石U-PB年龄限制了碎片，泥质材料的出处，塑造沉积物，西部印度河的投入（例如，Narmada和塔蒂河），以及来自Deccan Trap的一些材料。在Breccias内发现的碳酸盐嵌段是来自外部印度欧式架的浅水石灰岩，其在中间后期的增强碎片沉积物递送中被过度曝光。由于有靠近载玻片来源的现代内部地震，材料的最终施加可能与地震性有关。虽然我们假设未来批量浪费事件的风险低，但应该指出的是，世界各地的其他超透明的大陆边缘可能面临大众失败的风险，就像Nataraja幻灯片一样大。

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    《Oceanographic Literature Review》 |2020年第5期|778-781|共4页
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