西南日本内帯ジュラ紀付加複合体の広域対比(ジュラ紀付加体の地域地質と広域対比)(ジュラ紀付加体の起源と形成過程)  [in Japanese] Regional correlation of the Jurassic accretionary complex in the Inner Zone of Southwest Japan(Regional geology and correlation)(Origin and evolution of Jurassic accretionary complexes in Japan)  [in Japanese]

西南日本内帯のジュラ紀付加複合体(丹波-美濃-足尾テレーン)は, 東西延長1,000km以上, 南北幅約150kmに及ぶ広い範囲に露出している.最近の約20年間に公表された文献を編集・総括することで, 以下の特徴を明らかにした.(i)各地域でのジュラ紀付加複合体は, 岩相組合せ・堆積年代・地質構造の特徴に基づいて, 複数の構造層序単元(コンプレックス)に区分される.(ii)これらのコンプレックスは上述した記載的特徴の類似性から, α型〜ζ型に分類できる.(iii)それぞれの型のコンプレックスは, その固有の海洋プレート層序を持っている.(iv)それぞれのコンプレックスの分布には, 規則性がある.(v)ジュラ紀付加複合体はさらに, 整然相・破断相・混在相に分類できる.(vi)α1型・β1型・β2型のコンプレックスは整然相を主体とし, その他の型のコンプレックスでは混在相が卓越している.これらの特徴から, 付加作用が起こる位置と, 整然相/混在相の割合や付加された粗粒砕屑物の量が, 時代の経過とともに変化したことが読み取れる.

The Jurassic accretionary complex, called the Tamba-Mino-Ashio Terrane, in the Inner Zone of Southwest Japan is widely exposed over a length of more than 1,000 km with a width of about 150 km. A compilation of the exhaustive literature spanning the last two decades, reveals the following aspects : (i) the Jurassic accretionary complex in eight surveyed areas is divided into several tectonostratigraphic units, on the basis of lithologic association, depositional age and structural features; (ii) these units are grouped into type α to ζ complexes on the basis of similarity in their descriptive features, i.e., type α is characterized by Late Jurassic clastic rocks and Triassic to Jurassic cherts, type β is composed of Middle Jurassic clastic rocks and Triassic to Jurassic cherts with basaltic rocks and limestones, types γ and δ consist of Middle Jurassic clastic rocks, Carboniferous and/or Permian to Jurassic cherts, and Carboniferous and/or Permian basaltic rocks and limestones, and types ε and ζ are composed of Early to Middle Jurassic clastic rocks, Carboniferous and/or Permian to Jurassic cherts and Carboniferous and/or Permian basaltic rocks and limestones; (iii) each of the complexes has its own oceanic plate stratigraphy; (iv) each type occurs in a particular manner, e.g., type α and types ε and ζ are exposed respectively in eastern and western areas in the Inner Zone, while type β occupies nearly half of the terrane, cropping out everywhere from eastern to western areas; on the other hand, (v) the Jurassic accretionary complex is also classified into coherent, broken and mixed facies on the basis of fragmentation and mixing of strata; and (vi) types α1,β1 and β2 mainly consist of the coherent facies, whereas the mixed facies predominates over the coherent and broken facies in the other types.Considering the above features, the following accretionary history of the Tamba-Mino-Ashio Terrane is suggested; firstly in Early Jurassic time, the complexes presented by types ε and ζ were accreted in the western area of the Tamba-Mino-Ashio Terrane, in Middle Jurassic time the voluminous accretion of the complexes such as types δ, γ and β subsequently occurred in a wider area, and finally the youngest complexes, type α, accreted to the eastern area in the Late Jurassic time. During these processes, the volume of coherent facies and coarse clastic sediments suddenly increased in Middle Jurassic time, pointing to some kind of a major tectonic change.