Structural characteristics of shallowly buried accretionary prism: Rapidly uplifted Neogene accreted sediments on the Miura‐Boso Peninsula, central Japan
Structural characteristics of shallowly buried accretionary prism: Rapidly uplifted Neogene accreted sediments on the Miura‐Boso Peninsula, central Japan
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DOI：
10.1029/2005tc001823
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发表时间：
2005-10
期刊：
影响因子：
4.2
通讯作者：
Y. Yamamoto;H. Mukoyoshi;Y. Ogawa
中科院分区：
文献类型：
--
作者：
Y. Yamamoto;H. Mukoyoshi;Y. Ogawa
日本中部三浦半岛和房总半岛上的上中新统Misaki和Nishizaki组保存了一个刮下的增生棱柱的变形特征。在这项研究中阐明了与古温度和埋藏深度估计有关的空间分布，几何形状和与加积有关的变形风格。变形结构和纹理与现代增生棱柱体相似。最高古温度低（<50°C），保存的孔隙度高（30-50%），表明最大埋深小于1000 m。根据变形方式，将该断屑体自下而上划分为叠瓦状逆冲断层、逆冲单元和上相干单元。叠瓦状逆冲断层对应于基底滑脱带的分支，并被细分为角砾带、主断层泥带和剪切带。逆冲单元集中了形成各种级别的双重结构的逆冲系统，而上相干单元的特征是重力不稳定和地震引起的变形，而没有逆冲断层。与刮离过程相关的双重分布、剪切应变和流体迁移清楚地定位在叠瓦状逆冲断层和逆冲单元内。这种与加积有关的变形发生在沉积物石化之前，并在剪切变形、沉积序列增厚和地震引起的液化引起的高流体压力下发生。这些过程控制了增生棱柱体早期变形的方式和逆冲推覆位置。
The upper Miocene Misaki and Nishizaki formations on the Miura and Boso peninsulas in central Japan preserve the deformation features of an off‐scraped accretionary prism. The spatial distribution, geometry, and style of accretion‐related deformation with paleotemperature and burial depth estimation are elucidated in this study. The deformation structures and textures are similar to those of modern accretionary prisms. The low maximum paleotemperature (<50°C) and high preserved porosity of the sediments (30–50%) imply a maximum burial depth of less than 1000 m. On the basis of the mode of deformation, this off‐scraped body is divided into an imbricate thrust, a thrust unit, and an upper coherent unit in ascending order. The imbricate thrust corresponds to a branch from the basal décollement zone and is subdivided into a brecciated zone, a main gouge zone, and a shear band zone. The thrust unit hosts a concentration of thrust systems that form various orders of duplex structures, while the upper coherent unit is characterized by gravitational instability‐ and earthquake‐induced deformation without thrust faulting. The duplex distribution, shear strain, and fluid migration associated with the off‐scraping processes are clearly localized within the imbricate thrust and thrust unit. This accretion‐related deformation occurred before lithification of the sediment and under high fluid pressure induced by shear deformation, thickening of the sedimentary sequence, and earthquake‐induced liquefaction. These processes are inferred to control the effect on the mode of deformation and the location of thrusting during early deformation of the accretionary prism.