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ORIGIN AND PALEOGEOGRAPHIC TRANSITION OF THE SOUTH KITAKAMI BELT,NORTHEAST JAPAN

日本东北部南北上带的起源与古地理变迁

基本信息

批准号：
07640593
负责人：
EHIRO Masayuki
金额：
$ 1.41万
依托单位：
TOHOKU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

To clarify the origin and paleogeographic transition of the South Kitakami Paleoland, the Early-Middle Paleozoic geotectonic history and Paleozoic biogeography of the South Kitakami Belt were studied.The South Kitakami Belt is a part of the continent, South Kitakami Paleoland, having pre-Silurian (Caledonian) basement rocks : the high P/T type Matsugadaira-Motai Metamorphic Rocks, which were metamorphosed at about 500 Ma, Ordovician Hayachine Complex, late Ordovician (440 Ma) Hikami Granites and Shoboji Diorites. The basements are covered by the unmetamorphosed shallow marine sedimentary rocks ranging fron Silurian to Lower Cretaceous. Based on the Paleozoic geotectonic histort and paleobiogeography, the basements are considered to had been formed, during Cambrian to Ordovician time, in an accretionary prism situated at the northern margin of the Gondwanaland. It might be an extension of the South China Accretionary Fold Belt or Adelaide Fold Belt of eastern Australia.The South Kitakami Paleoland, together with the South China, was separated from the southward migrating Australia (Gondwanaland) during the Carboniferous. Permian and Triassic ammonoid paleobiogeographic data implies that the South Kitakami Pleoland was located in the equatorial Tethys and closely situated with South China and Southern Primorye during Middle to Late Permian time. North China differs from South China and South Kitakami in that the Lower Permian strata of the northern margin of the North China yield Boreal ammonoids and no Middle Permian paraceltitid have been reported from there. The close geographic relationships among South China, Southern Primorye and South Kitakami, especially between the latter two had persisted at least until Middle Triassic.

为明确南北上古陆的起源和古地理过渡，对南北上带早-中古生代大地构造史和古生代生物地理学进行了研究。南北上古陆是南北上古陆的一部分，具有前志留纪（加里东期）基底岩：500 Ma左右变质的高P/T型松田-摩台变质岩、奥陶系哈亚契纳杂岩、晚奥陶世（440 Ma） Hikami花岗岩和Shoboji闪长岩。基底被志留纪至下白垩世未变质的浅海沉积岩覆盖。根据古生代大地构造史和古生物地理学，认为该基底形成于寒武纪至奥陶纪，位于冈瓦纳大陆北缘的一个增生棱镜中。它可能是华南增生褶皱带或澳大利亚东部阿德莱德褶皱带的延伸。南北上古陆与华南在石炭纪与向南迁移的澳大利亚（冈瓦纳陆）分离。二叠纪和三叠纪氨气古地理资料表明，在中晚二叠纪时期，南北上洼洼位于赤道的特提斯，与华南和南滨海紧密相连。华北与华南和南北上的不同之处在于，华北北缘下二叠统地层产北方菊石，未见中二叠统副菊石的报道。华南与南滨海和南北上的密切地理关系，特别是后两者之间的密切地理关系，至少持续到中三叠世。