Tectonic Development of the Tokachi Plain-Differentiation of the Obihiro Basin and the Makubetsu Plateau
Tectonic Development of the Tokachi Plain-Differentiation of the Obihiro Basin and the Makubetsu Plateau
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十胜平原的构造发育——带广盆地与幕别高原的分异
DOI：
10.4116/jaqua.23.233
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发表时间：
1985
期刊：
影响因子：
--
通讯作者：
Itsumi Matsuzawa
中科院分区：
文献类型：
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作者：
Masaru Matsui;Itsumi Matsuzawa
本文根据十胜平原中部牧别高原上上新世-晚更新世沉积的地质关系，以及沉积物中8个层位的火山碎屑物和黑曜岩卵石的K-Ar年龄资料，报道了这些沉积的地层、时代和构造运动。上新世-早更新世十胜群分布于该高原，自下而上划分为池田组和小泽内组。根据软体动物和有孔虫动物群、古地磁地层学和K-Ar年龄资料，池田组的时代与上新世晚期相对应，而小乘内组的时代与早更新世相对应。小泽内组是由碎屑岩和火山碎屑岩组成的，是在池田沉积盆地中心西移后形成的浅海和陆盆中堆积而成.大鹿内组沉积后，牧别高原变为隆起区，而带广盆地仍为相对沉降区。牧别高原西缘沿着有一条活动构造线，称为奥里部断层。值得注意的是，厚的fanglomeratic沉积物，Kochien砾石层，遍布整个高原。该砾石层的岩相特征表明，西部腹地日高带在中更新世曾遭受过强烈的剥蚀。一些较年轻的砾石和火山碎屑沉积物覆盖在被切割的科钦砾石层上。较年轻的砾石层是由较老的厚砾石层经侵蚀和再沉积而形成的扇面沉积。对该地区及其周围的Kochien砾石层的上表面和基底高度的区域变化进行了严格的分析，以检测上新世晚期至全新世的构造运动，这些构造运动使砾石层发生位移和变形。研究结果表明，奥里贝断层的活动具有右旋走滑分量，自早更新世以来垂直分量逐渐减少。此外，值得注意的是，织部活动断层似乎起源于沿着之间的边界，日高和Tokoro带。
The purpose of this paper is to report the stratigraphy, age and tectonic movement of the Pliocene-Late Pleistocene deposits on the Makubetsu Plateau in the central region of the Tokachi plain on the basis of the geological relations of these deposits and K-Ar age data of the pyroclastic materials and obsidian pebbles collected from 8 horizons in these deposits.1. The Tokachi Super Group, Pliocene-Early Pleistocene, distributed in this Plateau, is divided into the Ikeda and the Osarushinai Formations in ascending order. According to the molluscan and foraminiferal fauna, paleomagnetic stratigraphy and K-Ar age data, the age of the Ikeda Formation is correlative to the latest Pliocene, and the Osarushinai Formation to Early Pleistocene. The Osarushinai Formation, composed of clastic and pyroclastic materials, was accumulated in shallow sea and terrestrial basin formed subsequently by the westerly shifting of the center of the Ikeda depositional basin.2. The Makubetsu Plateau was transformed into an upheaving area after the deposition of Osarushinai Formation, while the Obihiro Basin remained as a relatively subsiding area. Along the western margin of the Makubetsu Plateau runs an active tectonic line called Oribe Fault.3. It is noticeable that the thick fanglomeratic deposits, the Kochien Gravel Bed, prevail throughout this Plateau. The lithofacies of this Gravel Bed suggest that the western hinterland, Hidaka Belt, was eroded away vigorousely in Middle Pleistocene. Some younger gravels and pyroclastic deposits cover the dissected Kochien Gravel Bed. Those younger gravel deposits are fan-surface deposits formed by erosion and resedimentation of the older thick gravel bed.4. The areal changes in the altitudes of both the upper surface and the basal level of the Kochien Gravel Bed in and around this area have been critically analyzed to detect the Late Pliocene to Holocene tectonic movements which displaced and deformed this gravel bed. It has been disclosed as a result of this study that the activity of the Oribe Fault has a right-lateral strike-slip component and shows a vertical component decreasing gradually since Early Pleistocene. Moreover, it is worth notice that the Oribe active fault appears to have originated along the boundary between the Hidaka and Tokoro belts.