The Journal of the Geological Society of Japan

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In the present article, the writer has attempted to give an account of a preliminary survey of the Pliocene Foraminifera from Japan., The materials examined are derived from many geographically isolated localities, and are classified into the following 18 faunal associations., (A) Foraminifera-Province of the Japan sea (Ura-Nippon) type., Of many different species of Foraminifera distinguished up to the present time from the Japanese Pliocene, some species are found to be short-lived and distributed only in the northern Japan (Ura-Nippon), and are not known from the Pacific side of Japan., These characteristic species are listed in Table 3., In the present province, 9 faunal associations are included., 1., Anden association., A study of Foraminifera collected from the Pliocene of the Oga Peninsula has led the writer to the recognition of three foraminiferal associations., Anden association comprises the fauna of the "Sibikawa" beds as defined by OHASI and TOYAMA., 2., Wakimoto association is for the Foraminifera fauna of the "Wakimoto" sandy shale defined by OHASI and TOYAMA., 3., Taya association comprises the fauna from the "Kitaura" beds as defined by OHASI and TOYAMA in Oga Peninsula and "Taya" beds of K., HATAI in Iwami-Sannai-mura, Kawabe-gun, Akita prefecture., 4., Setana association is divided into three subassociations-Kuromatunai, Hanaisi and Setana ; the faunule from the districts of Hanaisi and Setana, composed of several characteristic forms of the Cassidulinidae and Polymorphinidae, should be considered to mark the northern limits of the "Cassidulina province of the Japan Sea type", and may be correlated to the Wakimoto and Daisyaka associations, while that from Kuromatunai is related to both the Japan Sea and Pacific types, and may be comparable with the Anden association in Oga Peninsula or Naganuma association in the Miura Peninsura., 5., Daisyaka association is from a comparatively coarse grained sandstone exposed in the region of Utimanbegawa, Higasi-Turuga-gun, Aomori prefecture; the fauna seems to be closely related to that of Wakimoto association on one hand and that of the Onma or Natukawa on the other., 6., The materials of the Natukawa association are derived from Natukawadani and Simotaka-mati, Kitadyo-mura, Kariha-gun, Niigata prefecture, both belonging to the "Natukawa" beds as defined by OMURA and CHITANI., 7., Sawane association from the Pliocene of Sawane, Sado Island, may be correlated to the Natukawa association., 8., Tagawa association comprises the fauna of the "Tagawa" beds as defined by T., ONOYAMA., It may be slightly younger than the Natukawa or Onma which are widely distributed in the Provinces of Kaga, Noto, Etizen and Etigo, and should be correlated to that of Anden in Oga Peninsula., 9., Onma association is for the Foraminifera fauna of the "Onma" beds defined by T., ONOYAMA., It is closely related to that of Natukawa and also to those of Kakegawa in Sizuoka prefecture., (B) Foraminifera-Province of the Pacific (Omote-Nippon) type., The fossils of the Nodosariidae found in the Neogene of Japan mostly belong to recent species, but there are many forms not hitherto recorded from the surrounding seas., Of them, 18 species ; namely Robulus costatus (F., & M., ), R., costatus subdecoratus (CUSHMAN), R., costatus multicostus (CUSHMAN), R., abensis ASANO, R., papillosus (CUSHMAN), R., tumidus ASANO, R., surugaensis ASANO, R., calcarioides ASANO, R., bicostatus ASANO, Pianularia japonica (ASANO), P., kakegawaensis (ASANO), P., boso ASANO, P., yabei ASANO, Lenticulina kamakuraensis ASANO, Vaginulina boso ASANO, V., miuraensis ASANO, V., awaensis ASANO, V., tibaensis striata ASANO are distributed only in the Pliocene of the Pacific side and not known from the Japan Sea side. [the rest omitted]

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A peculiar formation was recently reported from Kamimasuki-gun, Kumamoto-ken, central Kyusyu by certain geologists working on Southwest Japan., And the present paper is a report of our preliminary study on it., The complex is here called provisionally the Mizukosi formation., It is a thick series of slaty shale with intercalating members of conglomerate and sandstone and containing lenses of limestone., It is noteworthy that the conglomerate contains iu abundance rounded pebbles, cobbles, and boulders of granite and altered green andesites or porphyrites ; and the material of sandstone is also grains derived mainly from similar igneous rocks., Through the study of fossils (see list in the Japanese text) found in the limestone, we have ascertained that the formation belongs to the upper Titibu system, i., e., the Permian., In conclusion, we have pointed out several geological problems related to the Mizukosi formation., Among them the question of Palaeozoic igneous aetivity in the Japanese Islands may be the most interesting.,

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