Study on the Tectonics and Sedimentation of the Arc-arc Collision Type sedimentary Basins

由于菲律宾海板块向西北方向移动，南大福萨岛被认为是一个由属于古伊祖-博宁弧的岛屿组成的区域，这些岛屿由于菲律宾海板块的西北方向移动而碰撞并吸积到本州弧上。15 Ma以后有4次。这项研究的目的是阐明多重碰撞构造与南大窝区沉积作用的关系。主要研究成果如下：(1)与坦泽地块碰撞有关的海槽充填物主要由浊积岩和碎屑岩组成。它们显示出碎屑类型的变化趋势和向上的粗化序列，反映了根据坦泽地块的碰撞而发生的腹地的隆起运动。(2)对三坂地块(二次碰撞)的地质特征认识不清。沉积学研究表明，三阪地块由一套弧前、火山弧和弧后裂谷带构成。(3)被认为是南大福萨地区第一个碰撞地块的库什加塔雅山地块主要由重沉积的透明碎屑岩和物质流沉积组成。这些事实表明，草山地块一定是一个弧前或弧后地区。(4)根据古地磁研究，分布在Tonoki-Aikawa构造线以北地区的一些2 Ma以上的岩墙顺时针旋转了约34度。这表明，本州弧形的一部分是顺时针旋转的，并伴随着地块。

The south Fossa Magna is well known as a zone consisting of islands which belonged to the paleo-Izu-Bonin arc and collided and accreted to the Honshu arc due to the movement of the Philippine Sea plate in a north-west direction. There were four times after 15Ma. The purpose of this study is to clarify the relationship between multiple collision tectonics and sedimentation in the South Fossa Magna. The results are summarized as follows.(1) The trough-fill sediments related to the collision of the Tanzawa block are mainly composed of turbidite and debrite. They show a trend of change of clast type and upward coarsening sequences reflecting the upheaval movement of the hinterland according to the collision of the Tanzawa block.(2) The geological features of the Misaka block (second collision) was not well understood. Sedimentological studies clarified that the Misaka block constitutes a set of forearc, volcanic arc and backarc rift zone.(3) The Kushigatayama block that was thought to be the first collided massif in the South Fossa Magna is mainly composed of re-sedimented hyaloclastite and mass flow deposits. These facts show that the Kushigatayama block must have been a forearc or backarc region.(4) some of the dykes older than 2Ma, distributed in the area to the north of the Tonoki-Aikawa tectonic line, rotated clockwise about 34 degrees based on paleo-magnetic studies. This indicates that part of the Honshu arc rotated clockwise accompanied by the blocks.