Permian and Triassic submarine landslide deposits in a Jurassic accretionary complex in central Japan
Permian and Triassic submarine landslide deposits in a Jurassic accretionary complex in central Japan
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日本中部侏罗纪增生杂岩中的二叠纪和三叠纪海底滑坡沉积物
DOI：
10.1007/978-94-007-2162-3_57
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
H
中科院分区：
文献类型：
--
作者：
Kojima;S. and Sano;H
日本中部米诺地体的岩石主要由二叠纪玄武岩、下二叠世至早侏罗世深海放射虫硅质岩和后侏罗世陆源岩组成。混杂岩将这些二叠纪到侏罗纪的岩块合并到中到上侏罗世页岩基质中，也是地体的主要成分。根据岩性、时代和构造，米诺地体岩石被解释为侏罗纪增生杂岩。硅质岩单元包含两条证据，表明海底滑坡事件在二叠纪和三叠纪期间断断续续地发生在大洋中部地区。首先，上中下二叠统硅质岩单元包括重新沉积的碳酸盐，这些碳酸盐以海底碎屑和浊流的形式从海山顶部的浅海堆积物向下输送到硅质岩聚集的下侧。其次，尽管大多数米诺地体远洋硅质岩相缺乏粗大的陆源碎屑颗粒，但中上三叠统的硅质岩中含有薄层和碎屑纹层。这些颗粒为砂粒到颗粒大小的多晶颗粒，由硅质岩、硅质页岩、基性或中基性火山岩、蚀变火山玻璃、多晶石英和类海绿石矿物组成。这些碎屑沉积被解释为代表海底滑坡沉积的远端相，最有可能来自附近的海洋岛屿。在俄罗斯远东侏罗纪增生杂岩中的中三叠世深海硅质岩中也发现了类似的碎屑沉积层。
Rocks of the Mino terrane, central Japan, are composed mainly of Permian basalts capped by shallow-marine limestone, Lower Permian to Early Jurassic deep-sea radiolarian chert, and post-Early Jurassic terrigenous rocks. Mélanges incorporating blocks of these Permian to Jurassic rocks within a Middle to Upper Jurassic shale matrix are also major components of the terrane. The Mino terrane rocks are interpreted as Jurassic accretionary complexes on the basis of their lithology, age, and structure. The chert units contain two lines of evidence for submarine landslide episodes that occurred intermittently in mid-ocean regions during the Permian and Triassic. First, the upper Lower to middle Middle Permian chert unit incorporates resedimented carbonates, which were transported in submarine debris and turbidity flows from a shallow-marine buildup on the top of a seamount, down onto its lower flank, where the cherts were accumulating. Second, although most of the Mino terrane pelagic chert facies lack coarse land-derived clastic grains, the Middle to Upper Triassic chert contains thin beds and laminae of clastic debris. These grains are sand- to granule-sized and polymictic, consisting of chert, siliceous shale, basic or intermediate volcanic rocks, altered volcanic glass, polycrystalline quartz, and a glauconite-like mineral. These clastic sediments are interpreted as representing the distal facies of submarine landslide deposits, most likely derived from nearby oceanic islands. Comparable clastic sediment layers are also found in Middle Triassic deep-sea chert in a Jurassic accretionary complex in Far East Russia.