東シナ海堆積盆地と中部九州地溝  [in Japanese] Relationship between sedimentary basins on the shelf area in the East China Sea and the Central Kyushu Rift Valley  [in Japanese]

松本(1979)によって提唱された別府島原地溝をここでは中部九州地溝と呼ぶ。本構造は沖縄トラフと密接な成因的並びに構造発達上の関係があるが, 東シナ海陸棚上の堆積盆地とは一見何の関係も無いように見える。しかし, 中部九州地溝の基盤地質の構造上の特徴を見ると, 多くの点で東シナ海や朝鮮半島と共通性が認められる。中部九州の基盤地質の最も重要な特徴は, (1)先中新世堆積盆地が平行配列を示す主断層と密接な関係を以て発達すること, (2)これらの堆積盆地は断層側に堆積心を持ち, 南東へ傾斜する基盤上のhalf-graben 構造を示すこと, である。これらの特徴は, 東シナ海や朝鮮半島の後期中生代〜漸新世堆積盆地の構造とも共通しており, それらも一般に横ずれ断層を伴っている。従って, このような基本構造が中新世初期に中部九州地溝のgraven状構造を発達させた遠因になっていると思われる。

The Central Kyushu Rift Valley originally proposed by Matsumoto (1979) as the Beppu-Shimabara Graben, is closely related to the Okinawa Trough in origin and development, but apparently bears no relation to any sedimentary basins on the East China Sea shelf area. However, geologic and tectonic features of the basement or the Central Rift Valley show many common characters with those of the East China Sea as well as of the Korean Peninsula. The most characteristic features or the basement geology are that, (1) pre-Miocene sedimentary basins are developed in close relation to major faults which are arranged in parallel to each other, and (2) these basins show a half-graben structure with southeastward-tilted basement and a depocenter along the fault. These features also characterize most of Late Mesozoic to Oligocene basins in the East China Sea and the southern Korean Peninsula. They are almost always closely associated with strike-slip faults. Therefore, these structures played a major role as a precursor for initiating the graben structure of the Central Kyushu Rift Valley, which started in the early Miocene time.