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

为了阐明南北上古陆的成因和古地理变迁，研究了南北上带早-中古生代大地构造史和古生代地理，南北上带是大陆的一部分，南北上古陆具有前志留纪（加里东期）基底岩石：高P/T型松岛平-莫泰变质岩，变质时间约为500 Ma，奥陶纪早钦杂岩，晚奥陶世（440 Ma）的彦上花岗岩和庄保寺闪长岩。基底上覆盖着志留纪至下白垩统未变质的浅海沉积岩。根据古生代大地构造史和古生物地理学资料，认为这些基底形成于寒武纪-奥陶纪，形成于冈瓦纳大陆北方边缘的增生棱柱体中。南北上古陆与南中国在石炭纪从南迁的澳大利亚（冈瓦纳大陆）中分离出来。二叠纪和三叠纪菊石古生物地理资料表明，南北上普莱奥兰在中晚二叠世位于赤道特提斯，与华南和滨海边疆区紧密相连。华北与华南、北上南部的不同之处在于华北北方边缘下二叠统产北方菊石，而没有中二叠统副菊石的报道。华南、滨海边疆区南部和北上南部之间，尤其是后两者之间的密切地理关系至少一直持续到中三叠世。

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.