日本産中新生 Cyclammina について

概要

論文の詳細を見る
The presence of living Cyclammina from the seas bordering Japan was recorded as early as 1884 by BRADY and later again by CUSHMAN in 1910., More recently, the Soyo-maru of the Imperial Fisheries Experimental Station in Tokyo, during oceanographical observations and dredge operations on the continental shelf sea of Japan, made a large collection of Cyclammina cancellata BRADY by which our knowledge has increased., In regard to the fossils of the genus, Y., OTUKA (1932) recorded Cyclammina trullisata (BRADY) from a Pliocene formation in the South of Sanuki-machi (Chiba-ken); this may be the only record from the Pliocene., According to N., IKEBE (1940), Cyclammina is very abundant in the Niigata oil-fields, especially in the Shiiya formation (sandstone, and an alternation of sandstone and shale, and underlying Kubiki formation (predominated by black shale), for which reason the name of Cyclammina-Zone was applied by him., Research on Cyclammina in the Institute of Geology add Palaeontology, Tohoku University, has resulted in the identification of six forms as shown in Table 1., These materials, except for one from the Miocene of the Joban coal-field, are all from the Niigata oil-fields and are believed to belong to the Cyclammina zone of N., IKEBE., Most of these six forms which represent new species are here treated as A, B, C, D, E, and forms., Their localities and distribution wuthin the formations are given in Table 2, and their characters are briefly mentioned below., Cyclammina A (C., cf., orbicularis BRADY) Test subglobosa, umbilicate, composed of 6-8 chambers surfaces mooth; sutures distinct, somewhat depressed, nearly straight; periphery broadly rounded, aperture a long slit at base of apertural face., Diamater 0.,5-1mm., This form is distinguishable from the typical orbicularis by the smaller size and fewer number of chambers., Cyclammina B (C., cf., compressa CUSHMAN) Test nautiloid, compressed, umbilicate, composed of 16-19 chambers 10 last coil, surface smooth; sutures sometimes indistinct, not depressed, peripheral margin subacute; aperture an elongated curved sliy at base of chambers which have supplementary pores in apertural face., Diameter 5-3mm., Distinguishable from compressa by its larger form., Cyclammina C (C., cf., pusilla BRADY) Test planospiral, compressed, peripheral margin acute, slightly lobulated; chambers about 12 inlast coil; sutures distinct, nearly straight not depressed, aperture a curved slit base of apertural face., Dmameter 1-2mm., Distinguishable from pusilla by its fewer number of chambers., Cyclammina D (C., cf., complanata YABE & HANZAWA) Its related species, complanata, was originally described from the Karisan shale in Taiwan (Formosa)., The present form differs from that species by the smaller size and sinuous sutures., Cyclammina E (C., cf., bradyi CUSHMAN) This from resembles bradyi, a species widely distributed in the North Pacific, but is distinguishable by its more compressed and nearly flat chambers., Cyclammina F., (C., cf., pauciloculata CUSHMAN) This from may be identical with pauciloculata, a species which is widely distributed both in the Pacific and Oceans., Stratigraphical significance., The six forms which can be distinguished from the living species, range from the Kubiki up to the Shiiya but have not been discovered in the still younger Ushigakubi and Shiraiwa formations., Elsewhere, none of these forms have been discovered in the Pliocene age., Cyclammina C was discovered in the Miocene Mizunoya sandstone and Misawa sandstone in the Joban coal-fields., This discovery shows that the age of the Kubiki and Shiiya is Miocene, in good accordance with the age indicated by fossil mollusks., A study of the stratigraphical range of the six forms in a limited area of the oil-fields, shows that certain forms are more adundant in the Kubiki than in the Shiiya, while others are more abundant in the latter than in the former., Accordingly, subdivision of the Cyclammina-zone of N
日本地質学会の論文
1949-02-20

著者

淺野清
東北大學理學部地質學古生物學教室

日本産中新生 Cyclammina について

スポンサーリンク

概要

著者

関連論文

スポンサーリンク