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III.—Geological Age of the Ogasawara Group (Bonin Islands) as indicated by the occurrence of Nummulites

Published online by Cambridge University Press:  01 May 2009

S. Yoshiwara
S. Yoshiwara
Affiliation:
Science College, Imperial University, Tōkyō, Japan.
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Extract

In the geotectonics of the Japanese Islands, neo-volcanic eruptions in chains parallel to the direction of their elongation play an important part. Dr. Harada has counted three of them on the north, and four on the south of Kwantō, where the mountain-systems of northern and southern Japan are confluent. Besides, there are three chains across Japan. They are (1) the Kirishima chain running from N.W. to S.E., in the southern part of Kyushū; (2) the Chishima chain in Hokkaidō running from N.E. to S.W.; and (3) the Fuji chain forming the boundary of northern and southern Japan (Fig. 1). In a part of the Myokō volcanic group forming the northern extremity of the last important chain, there are the volcanoes of Onigajō, Myokō, Kurohime, and Iijuna, all of which have erupted, according to Mr. Yamazaki, through the Neogene Tertiary (probably Miocene). The southern continuation of this group is that of Yatsugatake, consisting of about nine volcanoes. Further on the south stands Mt. Fuji, formed in the Pliocene or Diluvium, like its southern neighbour Ashitaka-yama, which, according to Mr. Hirabayashi, more early reposed. In the Hakone and Atami volcanoes, also in the Fuji chain, eruption took place, according to him, first in the Pliocene epoch, but chiefly in the Diluvial.

Type
Original Articles
Information
Geological Magazine , Volume 9 , Issue 7 , July 1902 , pp. 296 - 303
Copyright
Copyright © Cambridge University Press 1902

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References

page 296 note 1 Harada, : “Die Japanischen Inseln,” 1890.Google Scholar

page 296 note 2 Shima (pronounced Jima in combination) means island or islands.Google Scholar

page 269 note 3 Harada, : “Die Japanischen Inseln,” 1890.Google Scholar Kikuchi, , “On Pyroxenite Compounds in certain Volcanic Rocks from Bonin Island”: Journ. Coll. Sci. Imp. Univ., vol. iii (1890).Google Scholar

page 297 note 1 , Suzuki, “Petrography of the Bonin Islands” (in Japanese): Bull. Geol. Soc. Japan, vol. i, No. 1 (1885).Google Scholar

page 300 note 1 Fennema, Verbeek et: “Description géologique de Java et Madoura,” t. ii (1896).Google Scholar

page 301 note 1 Localities of Orbitoides in Japan had been confined to Nakakosaka in Province Kōtsuke and Kawaguchi in Province Kai, prior to my journey to Formosa and Riukiu (Loochu) Islands in 1899. Specimens found in Nakakosaka have been determined by Jones as O. (Discocyclina) dispansa, Sow., but afterwards as Lepidocyclina by Verbeek. I collected numerous specimens from the limestone in Iriomote-jima in RiukiuGoogle Scholar (Journ. Coll. Sci. Imp. Univ. Tōkyō, vol. xvi, pt. 1, art. 2, 1901). By my latest researches I am convinced that all these Orbitoides of the above three localities belong to Lepidocyclina. Besides, Messrs. R. B. Newton and R. Holland found a species of Lepidocyclina (O. Verbecki, Newt. & Holl.) in a slide of Formosan limestone (Journ. Geol. Soc. Tōkyō, vol. vii, No. 81, 1900).Google Scholar

page 301 note 2 Spelt Tosi-shima on map, Fig. 1, p. 298.Google Scholar