Study on Pull-Apart Basin along Median Tectonic Line

中构造线（MTL）沿线的伊泉沉积盆地（ISB）是一个典型的走滑盆地，近年来备受关注。本研究的目的是明确ISB的形成机制和ISB的变形风格，达到约300公里的长度。所得结果摘要如下1。ISB分区：编制了MTL断裂系统和上白垩统Izumi群分布的构造图。根据这张地图，ISB至少可以分成5段（A-E）。尽管Izumi Group的分布从a段（西四国）到D段（Izumi Mountains）是连续的，但预计每个段（次盆地）都有一个盆地的可能性。因此，本研究试图确定一些片段的年龄：到目前为止，从D段西部获得了77-72 Ma的裂变径迹年龄，从E段（Gojo以东）获得了Radioralia （Archeodictyomitra Sp等）。更多的（将被提交）ISB的形成机制：编制了MTL断层弯曲（Gojo弯曲）以西的D段构造图。在这个MTL的释放弯曲处，由左滑运动产生的复式构造已经变得清晰（《地质学》，第18卷，第392-394页，1990年；《构造地质学》，第392-394页）。35，第65-70页，1990年)。ISB可以看作是由MTL弯曲处的双工作用形成的拉分盆地。进一步探讨了拉分盆地的形成机制（构造地质，第2期）。（1991年第36期，印中）。ISB变形类型：d段泉群浊积岩相发育由重力引起的层理面滑动所产生的不谐褶皱和小尺度梯级断裂等变形构造。通过对它们的测量，得到了沿层理面剪切应变（gamma= 0.3—1.4）。利用扫描电子显微镜确定了滑块表面的滑移方向。从它们的证据和沉积中心的迁移来看，盆地内充填泉群的倾斜被认为是由沿MTL的走滑双重作用引起的（日本地质学会，关西分会论文集，第2卷）。109，第7页，1990；日本地质学会年会，第97届，摘要，p. 346, 1990；将提交)。少

The Izumi Sedimenatry Basin (ISB) along the Median Tectonic Line (MTL) has become of major interest lately as a typical strike-slip basin. The purpose of this study is to become clear formative mechanism for the ISB and deformational style in the ISB, attaining to about 300 km in length. A summary of the results obtained is shown below.1. Division of ISB : A tectonic map showing the MTL fault system and the distribution of the Izumi Group (Upper Cretaceous) was compiled. According to this map, the ISB is divisible into at least 5 segments (A-E). The possibility of a basin having liked with each segment (subbasin) is envisioned, though the distribution of the Izumi Group is continuous from segment A (west Shikoku) to segment D (Izumi Mountains). This study has hence tried to determine ages of some segments : Until now, the fission track age of 77-72 Ma from the western part of the segment D, and Radioralia (Archeodictyomitra Sp, etc.) from the segment E (far east of Gojo) were obtained. … More (will be submitted)2. Formative mechanism for ISB : A tectonic map in the segment D, west of a fault bend (Gojo bend) of the MTL, was also compiled. At this releasing bend of the MTL, duplex structures produced by left-slip movement have become clear (Geology, v. 18, p. 392-394, 1990 ; Structural Geology, no. 35, p. 65-70, 1990). The ISB can be regarded as a pull-apart basin formed by the duplexing at the MTL bend. The mechanism of pull-apart basin was further discussed (Structural Geology, no. 36, 1991, in press).3. Deformational style in ISB : Deformation structures, such as disharmonic folds and small-scale echelon faults, produced by gravity-induced bedding-plane slippages, are well developed in the turbidite facies of the Izumi Group in the segment D. By measuring for them, the shear stranin (gamma= 0.3--1.4) along the bedding plane was obtained. Using a scanning electron microscope, the slip direction on slickensides was determined. Judging from their evidence and the migration of depocenter, the tilting of the filling Izumi Group in the basin is thought to have been caused by strike-slip duplexing along the MTL (Geological Society of Japan, Kansai Branch Proceedings, no. 109, p. 7, 1990 ; Geological Society of Japan, Annual Meeting, 97th, Abstracts, p. 346, 1990 ; will be submitted). Less