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Volume 54, Issue 1
Displaying 1-10 of 10 articles from this issue
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Akihiko SuzukiArticle type: Article
2000 Volume 54 Issue 1 Pages 1-2
Published: January 25, 2000
Released on J-STAGE: July 14, 2017
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Nobuo Masai, Yoshiaki Ishida, Kazuyoshi Sase, Kiichi ObataArticle type: Article
2000 Volume 54 Issue 1 Pages 3-12
Published: January 25, 2000
Released on J-STAGE: July 14, 2017
JOURNAL OPEN ACCESSMany molluscan fossils were obtained from the Middle Miocene Yokozemachi Group, uppermost Neogene strata in the Chichibu Basin. The species found in these strata are mainly Ostrea gravitesta, Macoma optiva, M. izurensis, M. arctata, Cultellus izumoensis, etc. Based on these fossils, the paleoenvironment of the Yokozemachi Group varied from the lower sublittoral to intertidal zones, and the sea regressed gradually. The paleo-latitude of this area is infered to have been 34-35°N on the basis of the HDM-diagram made from molluscan data. The change of the paleogeography and the paleo-depth are constracted from the present data and the geological data of the Neogene Tertiary of the Chichibu Basin Research Group (1991, 1994). The sea might have opened to the southeast side during the stage of the Yokozemachi Group.View full abstractDownload PDF (1777K) -
Kaori SatoArticle type: Article
2000 Volume 54 Issue 1 Pages 13-22
Published: January 25, 2000
Released on J-STAGE: July 14, 2017
JOURNAL OPEN ACCESSLithostratigraphical and tephrostratigraphical study was carried out on the Kazusa and Shimosa Groups, which are the Middle to Upper Pleistocene around Kongochi, middle part of the Boso peninsula Japan. This paper presents the detailed geological map and cross sections. The Kazusa and Shimosa Groups in this study area have a northeast-southwest strike and a gentle dip to northwest. The dip has the ranges of 0.3°from 4°which is lightly continuously towards the upper formation. In addition, the formation around Osawa, located at the east part of the study area has slight dip, and swollen up structure as well. Basically, every formation stacks conformably in the study area, except that only the Kioroshi Formation unconformably overlies the underlying formations.View full abstractDownload PDF (1354K) -
Yasuhiro Takashimizu, Fujio Masuda, Masaaki TateishiArticle type: Article
2000 Volume 54 Issue 1 Pages 23-32
Published: January 25, 2000
Released on J-STAGE: July 14, 2017
JOURNAL OPEN ACCESSThe Makinohara Upland, central west Shizuoka Prefecture, central Japan, faces the Suruga Trough, which is formed by the subduction of the Philippine Sea Plate beneath the Eurasia Plate. The Upper Pleistocene of the Makinohara Upland consists of incised valley fills, which comprises a depositional sequence. Compositional trends of the sands from the Makinohara Upland area (Makinohara sands) are plotted in the Lt-rich field, within the lithic recycled-transitional field of Dickinson and Seely (1979) and Dickinson et al. (1983). The sands of the Makinohara Upland area and Kanto area show mineralogically immature trend than those of the U.S.A. (continental area). The Makinohara sands are deposited in fluvial environments during lowstand and highstand periods, and respectively have different plots on Qm-Fl-Lt and Ma (grain-size) versus Qm/(Qm+Lt) diagrams. The sands of the LST mostly have high Qm/(Qm+Lt) ratios (well matured), and those of the HST have low Qm/(Qm+Lt) ratio (poorly matured). The sands of tsunami deposits, which were deposited in a barrier sand body and a drowned valley environment of Makinohara Upper Pleistocene, are plotted in different fields on the diagrams of Ma versus Qm/(Qm+Lt). Those deposited in the drowned valley contain more monocrystalline quartz; those deposited in the barrier sand body contain more lithic fragments. The drowned-valley tsunamiite is plotted in a similar field to the drowned valley deposits. The tsunamiite in the barrier sand body is plotted in a similar field to the barrier sands and beach-shoreface sands. Relationships of grain-size characteristics and Qm/(Qm+Lt) plot do not show any clear correlation.View full abstractDownload PDF (1951K) -
Seiki Yamauchi, Hajime Sakanoue, Takeo Yoshioka, Hisashi Murakami, Hir ...Article type: Article
2000 Volume 54 Issue 1 Pages 33-42
Published: January 25, 2000
Released on J-STAGE: July 14, 2017
JOURNAL OPEN ACCESSThe Oki Islands, southern Japan Sea, is a key area for the study of tectonics and middle to late Miocene molluscan fossils. The Ichibu Formation in Nishi Island has been correlated with various Miocene stages in different papers. The upper part of the Ichibu Formation which was previously exposed in only a limited area. New outcrop arising from construction of the Setoyama Tunnel yielded many molluscan fossils. The assemblages of these fossils consist predominantly of Anadara tazawensis, with Kaneharaia kaneharai and Laevicardium shiobarense, and are thus correlated with the Shiobara Fauna. Consequently, the Ichibu Formation can be correlated with the Fujina and Zinzai Formations in eastern Shimane Prefecture. These formations also contain the Shiobara Fauna are estimated to be later Middle Miocene in age. The molluscan assemblages in the Ichibu Formation indicate an upper neritic zone strongly influenced by a cold current. The Ichibu Formation contains a bivalve which we tentatively identify as Mizohopecten cf. nakatombet-suensis. Based on the results of this study and drillcore of a deep well on Naka Island, the Miocene series of the Oki Dozen is divided into the Mita, Otsu, Ichibu and Ama Formations, and succeeding alkaline volcanic rocks, in ascending order.View full abstractDownload PDF (2202K) -
Masayuki Shimizu, Shoji Fujii, Toshikazu HamuroArticle type: Article
2000 Volume 54 Issue 1 Pages 43-48
Published: January 25, 2000
Released on J-STAGE: July 14, 2017
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Kanto Ash Layers Research Group, Volcanic Ash Research Subgroup of Sub ...Article type: Article
2000 Volume 54 Issue 1 Pages 49-54
Published: January 25, 2000
Released on J-STAGE: July 14, 2017
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Tsuneo Nakajima, Yoshitaka MatsuhashiArticle type: Article
2000 Volume 54 Issue 1 Pages 55-57
Published: January 25, 2000
Released on J-STAGE: July 14, 2017
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Akihiko SuzukiArticle type: Article
2000 Volume 54 Issue 1 Pages 58-59
Published: January 25, 2000
Released on J-STAGE: July 14, 2017
JOURNAL OPEN ACCESSDownload PDF (295K) -
Yuji SekiArticle type: Article
2000 Volume 54 Issue 1 Pages 60-61
Published: January 25, 2000
Released on J-STAGE: July 14, 2017
JOURNAL OPEN ACCESSDownload PDF (366K)
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