抄録
飛騨外縁帯・南部北上帯・黒瀬川帯の古生界は, 層相と化石相が互いに類似する.3帯の基盤は前〜中期オルドビス紀のオフィオライトからなる.中部オルドビス系〜デボン系は頁岩と酸性凝灰岩を主体とするメランジュまたはタービダイトからなり, それらの一部は高圧型変成岩類になっている.石炭・ペルム系は頁岩, 砂岩, 礫岩, 石灰岩などで構成される陸棚相浅海成層からなり, 特に石炭系は大量の火山砕屑岩類を伴う.これらの古生界は前期オルドビス紀に中朝地塊縁辺の沈み込み帯で形成されはじめ, ペルム紀には北半球中緯度に位置した中朝地塊の東縁大陸棚に堆積盆が存在したと推定される.3帯の構造の大枠は, 前期白亜紀(Valanginian)に複数のナップやクリッペを形成した東または南フェルゲンツの衝上運動, および前期白亜紀(Aptian-Albian)の棚倉-中央構造線沿いの約1,500kmの左横ずれ運動によって形成した.
The Palaeozoic of the Hida Gaien, South Kitakami and Kurosegawa Belts resembles well each other in litho- and biofacies. The basement of the three belts comprises early to middle Ordovician ophiolite. The overlying middle Ordovician to Devonian formations comprise melange and turbidite, consisting mainly of shale and acidic tuff; and they have partly been subjected to high P/T type metamorphism. The Carboniferous and Permian formations comprise shallow marine continental shelf deposits, consisting of shale, sandstone, conglomerate and limestone, with a large amount of pyroclastic rocks in the Carboniferous. These Palaeozoic rocks were formed above a subduction zone along the Sino-Korean continental margin since early Ordovician. In Permian time, the sedimentary basin was probably placed on the continental shelf along the eastern margin of the Sino-Korean block, which was located at a middle northern palaeolatitude. The geotectonic framework of these belts was formed through early Cretaceous (Valanginian) east- or southward thrust movement which caused several nappes and klippes, and early Cretaceous (Aptian-Albian) left-lateral strike-slip faulting along the Tanakura-Median Tectonic Line. The left-lateral displacement along the Tanakura-Median Tectonic Line is estimated to be about 1,500km.
