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タイトル: 27. 足柄層に就いて
その他のタイトル: 27. Notes on the Asigara Beds
著者: 津屋, 弘逵
著者(別言語): Tsuya, Hiromichi
発行日: 1942年11月15日
出版者: 東京帝国大学地震研究所
掲載誌情報: 東京帝国大学地震研究所彙報. 第20冊第3号, 1942.11.15, pp.316-321
抄録: The lower-Pliocene Asigara beds, which are distributed in the area immediately northeast of the Hakone volcano, being overthrusted from the north by the Miocene Misaka series of the Tanzawa mountainland, may be divided accordiug to their lithic characters into upper and lower horizons, so far as their exposures along the Sakawa-gawa valley between Yamakita-mati and Koyama-mati are concerned. The upper horizon of the beds consists of an alternation of sandstone and conglomerate, carrying a large amount of both quartz-dioritic rocks and greenish metamorphic rocks, which have been derived probably from the Tanzawa quartz-diorite masses and the Misaka metamorphics respectively. The lower horizon of the beds consists of an alternation of conglomerate, almost entirely devoid of quartz dioritic pebbles, and sandstone rich in fragments of altered andesites. The interstices of the sandy particles in the conglomerate and the sandstone of the lower horizon are sometimes filled with patches and veins of secondary calcite. Although no distinct plane of disconformity between the upper and lower horizons of the Asigara beds has been ascertained, the boundary of the two horizons in the Sakawa-gawa valley may be placed provisionally about 100m east of Simizu-basi, midway between Yamakita and Koyama, where the upper falsebedded, more steeply dipped (50°~70°) sandstone and conglomerate, rich in the quartz-dioritic pebbles, rest on the lower, less steeply dipped (35°) sandstone and conglomerate, almost entirely devoid of the quartz-dioritic pebbles. Even if the Asigara beds represent a single formation in the lower Pliocene age, the above-mentioned differences between the upper and lower horizons of the beds seem to indicate some discontinuous changes, possibly due to crustal disturbances, in the conditions of sedimentation at some time during the deposition of the beds.
URI: http://hdl.handle.net/2261/10574
ISSN: 00408972


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