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转换，研究了南北上古生代早-中古生代大地构造史和古生代生物地理。北上南带是南北上古陆的一部分，具有前志留(加里东纪)基底岩石：500 Ma左右变质的高P/T型松原-墨台变质岩、奥陶纪Hayachine杂岩、晚奥陶世(440 Ma)Hikami花岗岩和Shoboji闪长岩。基底被志留系至下白垩统未变质的浅海相沉积岩覆盖。根据古生代大地构造史和古生物地理资料，认为这些基底形成于寒武纪至奥陶纪，形成于冈瓦大陆北缘的增生棱柱中。它可能是南中国增生褶皱带或澳大利亚东部阿德莱德褶皱带的延伸。南北上古奥兰德与南中国在石炭纪与向南迁徙的澳大利亚(冈瓦瓦兰)分离。二叠纪和三叠纪菊石古生物地理资料表明，南北上丘陵地块位于赤道特提斯山脉，与南中国和南山前两叠纪中、晚二叠世密切相关。北中国与南中国和南北上的不同之处在于，北中国北缘的下二叠统产北坡菊石，未见中二叠世副角石的报道。中国南部、滨海南部和北上南部之间的密切地理关系，特别是后两者之间的密切地理关系，至少持续到中三叠世。

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.