The Journal of the Geological Society of Japan
Online ISSN : 1349-9963
Print ISSN : 0016-7630
ISSN-L : 0016-7630
Volume 60, Issue 703
Displaying 1-6 of 6 articles from this issue
  • Tateo UEDA, Shin'ichi NISHIMURA
    1954 Volume 60 Issue 703 Pages 131-137
    Published: April 25, 1954
    Released on J-STAGE: April 11, 2008
    JOURNAL FREE ACCESS
  • Yu HIGUCHI
    1954 Volume 60 Issue 703 Pages 138-144
    Published: April 25, 1954
    Released on J-STAGE: April 11, 2008
    JOURNAL FREE ACCESS
    The Miyata formation occurs in the southern part of the Miura peninsula, Kanagawa prefecture, Japan., Since previous publications on this formation have described chiefly its Foraminifera and Mollusca, the principal purpose of this paper is to describe the environmental conditions under which the formation was deposited as determined from a study of foraminiferal assemblages., The Miyata formation consists of conglomerate and cross-bedded sandstone containing shells, which are overlain in succession by sandstone, an alternation of sandstone, and siltstone, and fossiliferous sandstone., The Miyata formation overlies the Hayama and Hayashi formations unconformably and the Kwanto volcanic ash overlies the Miyata formation unconformably., The Miyata formation is about 20 meters thick at the cliff at Okine (locs., 1, 2)., It is bounded on the north and south by vertical faults., Forminifera were collected from 19 different localities in the Miyata formation, but in all cases from the same stratigraphic horizon., These collections were compared with Recent Foraminifera from the tidal zone and inter-tidal region in the vicinity of the Miura peninsula to aid in the determination of the paleo-environment of the Miyata foraminiferal assemblages., The following conclusions were reached : 1) The foraminiferal assemblages of the Miyata formation comprise species flourishing in shallow water., The east and central parts of the Miyata formation are deeper than the western part in depositional facies, as inferred from the bathymetrical distribution of the Foraminifera., 2) The distribution of the Foraminifera within the Miyata formation shows an intimate relationship with the litho-facies, particularly with the grain size distribution of the rocks., 3) The temperature of the sea water at the time of deposition of the formation, as inferred from the Foraminifera, was somewhat lower than or nearly the same as the present sea water adjacent to the peninsula., 4) The fossil Foraminifera comprise an assemblage which lived near the shore of the open-sea.,
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  • Koichiro MASUDA
    1954 Volume 60 Issue 703 Pages 145-152
    Published: April 25, 1954
    Released on J-STAGE: April 11, 2008
    JOURNAL FREE ACCESS
    The Cenozoic strata in the areas of Machino-machi, Najimi-mura and Yanaida-mura, in Fugeshi-gun, Ishikawa Prefecture, are classified, on the basis of field observations, into the following formations, from lower to upper : Konosuyama volcanics : Comprised of andesite, basalt, dacite, agglomerates of andesite, basalt and dacite, and diorite., Part of the diorite is younger than the volcanics., Although the distribution of the various rock types has been mapped their stratigraphic sequence is not known., ., ., ., (stratigraphic relation unceertain) ., ., ., Toktunari formation : Comprised of pumiceous tuff and brecciated tuff with lenticular layers of tuffaceous sandstone, tuffaceous mudstone and conglomerate., Lignite seams and fossil shells are found in a few places., These rocks are intercalated between flows of andesite, basalt and dacite., ., ., ., unconformity ., ., ., Higashi-Innai formation : Comprised of mudstone, siltstone, sandstone and conglomerate in which lignite is intercalated., Fossils of Mollusca and Foraminifera are abundant., ., ., ., Awagura formation and Iwakurayama rhyolite : The Awagura formation is comprised of finely stratified white or light green colored pumiceous tuff, brecciated tuff and sandy tuff., The Iwakurayama rhyolite eruption is responsible for the large quantities of tuff in the Awagura formation, and consequently, the eruption took place during deposition of the Awagura., ., ., ., Najimi formation : Comprised of tuffaceous mudstone and tuffaceous siltstone, and locally contains pumice layers and laminated tuffaceous sandstone layers., Molluscan shells and sponge spicules occur throughout the formation., In the northern part of the areas, Radiolaria and Globigerina, are common and Conchocele is the outstanding megafossil., In the southern part of the areas, Foraminifera are abundant and Globigerina is also found., The occurrence of Globigerina suggests a free connection with the open sea., ., ., ., unconformity ., ., ., Okawa terrace deposits : Comprised of sand, gravel and clay in which fossils are absent., From fossil evidence, the Higashi-Innai formation, which has yielded Operculina, Miogypsina, Vicarya and others, is considered to be early Miocene in age., The Higashi-Innai formation contains rocks of marine and brackish-water facies as evidenced by fossils and lignite which contains sulphur., Among the geological structures of the district are several faults, and folding has occurred., Faults and fold axes trend east-west., The geological age of the folding and faults is considered post-Miocene and pre-Okawa time.,
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  • Takao YAMAGUCHI
    1954 Volume 60 Issue 703 Pages 153-159
    Published: April 25, 1954
    Released on J-STAGE: April 11, 2008
    JOURNAL FREE ACCESS
  • Shiro ISHIDA, Junji ITOIGAWA, Masao MORISHIMA, Akira MORISHITA, Keiji ...
    1954 Volume 60 Issue 703 Pages 160-166
    Published: April 25, 1954
    Released on J-STAGE: April 11, 2008
    JOURNAL FREE ACCESS
    The stratigraphy of the Cenozoic formations in Okuyamada, near Kyoto, Japan, has not been previously studied in detail, even though the locality has long been known to amateur fossil collectors as a unique source of marine molluscan fossils., The stratigraphy of the Tsuzuki group is as follows : Ofuku gravel (Pleistocene ?) ., ., ., unconformity ., ., ., Tsuzuki group Yuantani formation Tawara arkose sandstone and conglomerate Shiodani sandstone Okuyamada formation Kaya tuffaceous mudstone Miyamura sandstone bed Kawakami conglomerate ., ., ., unconformity and fault ., ., ., Chichibu Paleozoic formations The Yuantani and Okuyamada formations each represent a cycle of sedimentation., The geologic age of the Tsuzuki group is probably middle Miocene (F2-F3) because of the occurrence of Katelysia nakamurai, Protorotella yuantaniensis and Comptoniphyllum Naumanni, and also of species common to the Ayugawa and Mizunami groups.,
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  • Keiji NAKAZAWA
    1954 Volume 60 Issue 703 Pages 167-168
    Published: April 25, 1954
    Released on J-STAGE: April 11, 2008
    JOURNAL FREE ACCESS
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