八溝山地の中生界とユニット区分(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] Mesozoic strata in the Yamizo Mountains and their unit division(Regional geology and correlation)(Origin and evolution of Jurassic accretionary complexes in Japan)  [in Japanese]

西南日本内帯の丹波-美濃帯の北東延長部にある八溝山地には中生代堆積岩類が広く分布する.筆者等が先に行なった鶏足山塊のユニット区分を修正し, 新たに, 笠間・高取の2つのユニットを提唱した.両ユニットとも基本的にチャート-砕屑岩シーケンスからなるが, 高取ユニットではそのシーケンスが数回繰り返すことにより特徴づけられる.鶏足山塊における笠間・高取両ユニットの区分は岩相・構造的特徴から北方にある八溝・鷲子山塊にも適用できる.八溝山地の西方に位置する足尾山地も主に中生代付加堆積岩類からなるが, 岩相・年代的特徴から, 両山地は本来一連の中生代付加コンプレックスから構成されているものと考えられる.

The Yamizo Mountains at the northeastern corner of the Kanto Plain consists of four mountain blocks : the Yamizo, Torinoko, Keisoku, and Tsukuba Mountain Blocks from north to south. The northern three mountain blocks are made up mainly of Mesozoic sedimentary rocks which are regarded as the northeastern extension of those in the Tamba-Mino Terrane of Southwest Japan. We revised the tectono-stratigraphic units in the Keisoku Mountain Block, which were previously set up by us, and newly proposed the Kasama and Takatori Units, in structurally ascending order, herein.The Kasama Unit is composed of a chert-clastic sequence comprising bedded chert, shale, and coarse-grained clastic rocks in ascending order. The clastic rocks in this unit contain allochthonous blocks of limestone, chert and basaltic rocks. Middle to Late Triassic radiolarians and Late Jurassic radiolarians were recovered from cherts and clastic rocks in this unit, respectively. The Takatori Unit also consists of a chert-clastic sequence comprising "Toishi-type" siliceous shale, bedded chert, siliceous shale, and coarse-grained clastic rocks in ascending order, and is characterized by their repetitions. The "Toishi-type" siliceous shale contains late Early Triassic conodont fauna. Bedded chert of this unit yields Middle Triassic to Early Jurassic radiolarians. Furthermore, Middle to Late Jurassic radiolarian faunas were discriminated in the clastic rocks in this unit. The Kasama and Takatori Units are in fault contact with each other. The subdivision into two units in the Keisoku Mountain Block is further applicable in the Torinoko and Yamizo Mountain Blocks based on the lithological characteristics.