関東山地北東縁部の地質構造

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In the northeastern periphery of the Kanto Mountains, several sedimentary formations and various kinds of igneous and metamorphic rocks, ranging from pre-upper-Paleozoic(?) to Neogene, are developed. They are cut by several high-angled faults, among which the Naranashi Tectonic Line (KOKATSU et al., 1970) and the Matsuyama Tectonic Line (defined in this paper) are the significant ones. The Naranashi Tectonic Line, trending NW-SE, may be equivalent to the Median Tectonic Line of Southwest Japan. It divides the region into two districts; the northern one being made up of the Oppata granites (late Cretaceous?) and the southern one of the Sambagawa schists. There are some differences in the structure of the Miocene formations between the two districts. It is related probably to the different movements of the basement complex. In the northern district, that is the Hiki Highlands, the Miocene formations have a parallel folding structure, while they have a basin structure in the southern district. The Naranashi Tectonic Line arose within a period of the Late Cretaceous acidic igneous activities, and its later movement was remarkable in Miocene. The Matsuyama Tectonic Line with NS trend is supposed to run between the Hiki Highlands and the Yoshimi Highlands, the latter of which consists of the Sambagawa schists and such high-grade metamorphic rocks as amphibolite and two-mica gneiss as well as of the Neogene formations. Among them the high-grade metamorphic rocks are supposed to be a constituent of the deeper part of the area. The eastern side of this tectonic line, the refore, has been displaced about 10km northward since Miocene. The Matsuyama Tectonic Line is possibly apart of the Hachioji Tectonic Line which divides the Kanto Mountains and the Kanto Plains.
日本地質学会の論文
1976-12-30

関東山地北東縁部の地質構造

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