Spatial Distribution of Mass‐Transport Deposits Deduced From High‐Resolution Stratigraphy
Spatial Distribution of Mass‐Transport Deposits Deduced From High‐Resolution Stratigraphy
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从高分辨率地层学推论的物质输送沉积物的空间分布
DOI：
10.1002/9781119500513.ch4
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Yamamoto Yuzuru
中科院分区：
文献类型：
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作者：
Utsunomiya Masayuki;Yamamoto Yuzuru
基于丰富的火山灰标志层的成熟地层学揭示了日本中部暴露的更新世弧前盆地填充物内盆地范围（>10 km）的质量输送沉积物（MTD）的空间分布和起源（即，Kazusa集团）。Kazusa群中的10个地图比例的MTD根据其岩相和内部结构被分类为I型或III型。I型MTDs夹有砂岩和粉砂岩，通常为5-20 m厚的碎屑层，由泥砂基质中的块体和圆形砾石组成。II型MTDs夹有以粉砂岩为主的地层，厚度达100 m，由大型（>10 m）砂岩和粉砂岩交替块体组成。指标化石与标志层相结合，表明II型MTDs中的这些区块起源于更深的地层（海底以下60米以上）。第三类的特征是斜坡-平坦结构和重复的叠瓦状逆冲断层，在地图比例尺上可以识别。MTDs的形成显然与快速沉积和随后产生的超流体压力有关。这些发现是基于高分辨率地层学，这证实了从地层学的角度可以更全面地了解水下物质传输过程。
A well‐established stratigraphy, based on abundant tephra marker beds, has revealed the spatial distributions and origins of basin‐wide (>10 km) mass‐transport deposits (MTDs) within the Pleistocene forearc basin fill that is exposed in central Japan (i.e., the Kazusa Group). Ten map‐scale MTDs in the Kazusa Group were classified as either type I or III based on their lithofacies and internal structures. The type I MTDs were intercalated with alternating sandstone and siltstone and typically occur as 5–20 m thick layers of debrites consisting of blocks and rounded gravels within a muddy sand matrix. The type II MTDs were intercalated with siltstone‐dominated strata and reach 100 m in thickness and consist of large (>10 m) blocks of alternating sandstone and siltstone. Index fossils, combined with the marker beds, reveal that these blocks in the type II MTDs originated from deeper strata (>60 m below the seafloor). Type III is characterized by a ramp‐flat structure and repeated imbricate thrusts, identified at the map scale. The formation of the MTDs was apparently associated with rapid sedimentation and consequent generation of excess fluid pressure. These findings were based on high‐resolution stratigraphy, which confirms that taking a stratigraphic perspective can contribute to a more comprehensive understanding of subaqueous mass‐transport processes.