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Tectonics of eastern margin of the Asian continent

亚洲大陆东缘构造

基本信息

批准号：
09440175
负责人：
OTOFUJI Yo-ichiro
金额：
$ 6.21万
依托单位：
Kobe University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

项目摘要

We carried out our paleomagnetic study in Kitakami massif in Northeast Japan, Nohi area in easternpart of Southwest Japan, and Sikhote Alin mountain in Russia.Paleogene and early Cretaceous welded tuffs have been sampled from eleven sites at the Omoe Peninsula(39.6°N,142.0°E) in the Kitakami massif of northeast Japan for paleomagnetic study. Westerly declinations with shallow inclination are identified after tilt correction in the 62〜71 Ma Heizaki volcanics(D=283.5°,I=9.4°, αィイD295ィエD2=8.0°) and in the 114〜119 Ma Harachiyama Formation(D=274.2°, I=-20.4°). The shallow inclination indicates that the Kitakami massif was located in low latitude(5°±4°N) at 62〜71 Ma. Taking into account a reference paleomagnetic pole of the Paleocene expected from Sikhote Alin, the Kitakami massif was translated northward over 25° in latitude since 65 Ma. We conclude that the Kitakami massif was incorporated into Asian continent at some time between 30 Ma and 22 Ma before opening of the Japan Sea.We investig … More ate formation of the curvature of the Median Tectonic Line (MTL) in Southwest Japan. we carried out a paleomagnetic study in the Nohi area, north of the curved part of the MTL in the eastern part of Southwest Japan. Paleomagnetic data indicate that the Nohi area are experienced a clockwise rotation through more than 45° with respect to the Asian continent as a part of Southwest Japan but that the amount of rotation of the Nohi area is 23°smaller than that of the central part of Southwest Japan. A new model is developed to explain the tectonic rotation. At about 15 Ma during the latest stage of the clockwise rotation of Southwest Japan associated with opening of the Japan Sea, the eastern end moved southward by more than 60 km along a lest-lateral strike-slip fault which comprised the present north-south segment of the MTL and the Akaishi Tectonic Line. We conclude that the curvature of the MTL is a composite of the 15 Ma strike-slip fault system and a small bend of the MTL associated with the small differential rotation of the Nohi area with respect to the central part of Southwest Japan. Less

在日本东北部的北上海、东北部的能比地区和俄罗斯的SikhoteAlin山进行了古地磁研究，在日本东北部的北上海海的大生半岛（39.6° N，142.0 °E）的11个地点采集了古近纪和早白垩世熔结凝灰岩样品，进行了古地磁研究。倾斜校正后，在62 ~ 71 Ma的平崎火山岩（D=283.5°，I=9.4°，α_（12））D295 ~ D2=8.0°）和114 ~ 119 Ma的原山组（D=274.2°，I=-20.4°）中识别出了具有浅倾角的西风倾斜。浅倾角表明北上火山岩在62 ~ 71 Ma时位于低纬（5°±4°N）。考虑到Sikhote Alin古新世的参考古地磁极，自65 Ma以来，北上地磁极向北平移了25°。我们认为，北上裂谷是在日本海开放前30 ~ 22 Ma的某个时期并入亚洲大陆的，并对这一时期的构造活动进行了探讨 ...更多信息日本西南部中央构造线（MTL）弯曲的晚期形成。我们在日本西南部东部MTL弯曲部分以北的Nohi地区进行了古地磁研究。古地磁资料表明，能飞地区作为日本西南部的一部分，相对于亚洲大陆经历了超过45°的顺时针旋转，但能飞地区的旋转量比日本西南部中部的旋转量小23°。提出了一个新的构造旋转模型。在15 Ma左右，日本西南部顺时针旋转的最后阶段与日本海的开放，东端向南移动了超过60公里沿着一个横向走滑断层，其中包括现在的南北部分的MTL和赤石构造线。我们的结论是，MTL的曲率是一个复合物的15马走滑断层系统和一个小弯曲的MTL与小的差异旋转的能生地区相对于日本西南部的中部。少