姫島の地質構造と火山活動期

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Himesima, small island situated near the western border of the Inland Sea., B., KOTO'S paper "On the Volcano of Japan" (1916) has attracted the attention of many petrologists concerning the volcanic rocks in this island., Since the publications, though a few works on the petrology of the volcanic rocks has been reported by the other authers, but no study has been published from the stratigraphic point of view., The present paper is chiefly devoted to the description of the late Cenozoic sediments of this island, with special reference to the geologic structure and the age of the volcanic activity The stratigraphic sequence is summarized as follow: Himesima volcanics and tuff breccia unconformity Himesima formation Karato member (70m+) Maruisihana member (60+) Basement rock unexposed The Maruisihana member contains conspicuous amounts of pyroclastic materials and the uppermost part consist of a thick volcanic conglomerate, by which the Himesima formation is divided in to two members., These materials contain bear hornblend-andesite which is characteristic in the "Sanin Volcanic Zone"., On the contrary, the Karato member consists of an alternation of sand and mud containing little pyroclastic materials., The Himesima formation may be correlated with the neighbouring Turusaki formation which is considered to be early Pleistocene (I_2) in age., The geologic structure of the Himesima formation is characterized by the marked folding with axes running nearly N-S direction., Some parts are remarkably modified by the volcanic bodeis intruding anlong the anticlinal axes as shown in Fig., 3., The Himesima volcanics and tuff breccia rest on the Himesima formation unconformably and build up five cones., The age of this activity may be assigned to late Pleistocene (J_2〜J_3).,
日本地質学会の論文
1955-06-25

姫島の地質構造と火山活動期

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