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Volume 121, Issue 4
Displaying 1-5 of 5 articles from this issue
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Articles
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Yasufumi Satoguchi2015 Volume 121 Issue 4 Pages 125-139
Published: April 15, 2015
Released on J-STAGE: July 29, 2015
JOURNAL FREE ACCESSThe Plio-Pleistocene Kobiwako Group is a typical fluvio-lacustrine formation located at Lake Biwa, Japan. However, the stratigraphy of the lowermost part of this group contained inaccuracies. In this study, 33 tephra beds were examined to correct the stratigraphy and to investigate possible correlations among these beds and with other widespread tephras. As a result, six correlated tephra beds corrected the lowermost part of the group. A subsequent reassessment of the stratigraphy indicates that this group was formed at ca. 4.4 Ma in the eastern part of the area, and slightly later in the western part, due to constraints imposed by the terrain during this period.View full abstractDownload PDF (4803K)
Report
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Hiromi Nagahata, Teruaki Ishii, Soichi Omori2015 Volume 121 Issue 4 Pages 141-146
Published: April 15, 2015
Released on J-STAGE: July 29, 2015
JOURNAL FREE ACCESSWe describe the areal distributions and petrological characteristics of garnet-bearing acidic volcanic rocks at Mt. Kenashiyama, Fujikawaguchiko-machi, central Japan. The volcanic rocks are divided into three groups on the basis of lithology. Chemical analyses show that the rocks are mainly rhyolite. Their occurrences suggest that two of the groups are dikes or sills that are 50-100 m thick, with exposures 2-3 km wide.View full abstractDownload PDF (2939K) -
Katsuhito Soda, Tetsuji Onoue, Masayuki Ikeda2015 Volume 121 Issue 4 Pages 147-152
Published: April 15, 2015
Released on J-STAGE: July 29, 2015
JOURNAL FREE ACCESSTriassic bedded chert sequences in Jurassic accretionary complexes in Japan consist of centimeterscale rhythmic alternations of chert and shale beds that have been interpreted as recording astronomical cycles. Although the cyclostratigraphy was established in the Inuyama area of the Mino Belt, central Japan, the validity requires detailed cyclostratigraphic correlations to other Triassic bedded chert sequences in Japan. In this study, cyclostratigraphic analyses were performed on the Middle Triassic (Anisian) bedded chert sequence in the Tsukumi area of the Chichibu Belt, southwest Japan. The average duration of each chert-shale couplet is ca. 10 kyr, which differs to the ca. 20 kyr duration for the precession cycle during the Triassic, which was obtained by estimating the average duration of chert-shale couplets in the Triassic bedded chert sequence of the Inuyama area. The dominant cycles in a bed number series of thickness variations in the Middle Triassic chert beds are approximately 2-5, 10, 40, 200, 300, and 400 beds cycles, which partly differ from those of the Inuyama area.View full abstractDownload PDF (1941K) -
Takehisa Tsubamoto, Kunimatsu Yutaka, Hideo Nakaya, Tetsuya Sakai, Mot ...2015 Volume 121 Issue 4 Pages 153-159
Published: April 15, 2015
Released on J-STAGE: July 29, 2015
JOURNAL FREE ACCESSNew dental and astragalar specimens of a primitive hippopotamus, Kenyapotamus coryndonae (Mammalia, Cetartiodactyla, Hippopotamidae, Kenyapotaminae) from the lower Upper Miocene Nakali Formation at the Nakali locality, central Kenya, are described and illustrated. The new specimens increase the known morphological and size variations of the dentition and astragalus in this primitive hippopotamid species, which is important to understand the origin and early evolution of the Hippopotamidae.View full abstractDownload PDF (3655K)
Pictorial
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Asuka Yamaguchi, Manami Kitamura, Yohei Hamada, Yu Saitoh, Hideki Muko ...2015 Volume 121 Issue 4 Pages III-IV
Published: April 15, 2015
Released on J-STAGE: July 29, 2015
JOURNAL FREE ACCESSDownload PDF (6037K)
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