All issues
Volume 105, Issue 2
Displaying 1-8 of 8 articles from this issue
- |<
- <
- 1
- >
- >|
-
Yoshihisa Hiroki, Ryo Matsumoto1999 Volume 105 Issue 2 Pages 87-107
Published: February 15, 1999
Released on J-STAGE: April 11, 2008
JOURNAL FREE ACCESSRegression-and-transgression boundaries (RTBs) were defined in Miocene strata of the Yatsuo area (RTBs Y1, Y2, and Y3) in a backarc basin, the Mizunami area (RTBs M1, M2, and M3) in an intra-arc basin, and the Kakegawa area (RTBs K1 and K2) in a forearc basin, across central Honshu, Japan. The sedimentary successions of the Yatsuo and Mizunami areas consist of coastal-shelf deposits, and the RTBs are recorded as unconformities or ravinement surfaces. In the Kakegawa area, the middle of a turbidite section (RTB K1) and an erosional surface (RTB K2) in thick mudstone might represent maximum regressions.The recognized RTBs were formed in Miocene time, except for RTB M3 in Pliocene time. The Miocene RTBs can be correlated within four time zones by means of magnetostratigraphy ; Zone Jmi1 (RTB K1) in Chron C5Dn (17.62-17.28 Ma), Zone Jmi2 (RTBs Y1, M1, and K2) in Chron C5Br (16.01-15.16 Ma), Zone Jmi3 (RTBs Y2 and M2) in Subchron C5Bn1r (15.03-14.89 Ma), and Zone Jmi4 (RTB Y3) between 14.89 and 12.3±1.9 Ma. The synchronicities of the RTBs in Zones Jmi2 and Jmi3 in the different tectonic settings suggest that the RTBs were formed by regional sea-level changes.View full abstractDownload PDF (2911K) -
Hisatada Akahane, Takeshi Furuno, Hiroshi Miyajima, Michiharu Goto, To ...1999 Volume 105 Issue 2 Pages 108-115
Published: February 15, 1999
Released on J-STAGE: April 11, 2008
JOURNAL FREE ACCESSThe writer have soaked several wood pieces in the hot spring water stream (Tateyama Hot Spring Shin-yu) for 7 years where they had found the naturally silicified fallen wood. Weight percentages of silica in the experimented wood pieces increased from zero to ∼0.72%, ∼2.90%, 10.65%, 26.78% and 38.11%, after time intervals of 1, 2, 4, 5 and 7 years, respectively.Wood pieces were silicified by the precipitation of silica spheres in cell lumina of the wood tissue. Hot spring water and silica spheres passed through vessels and vessel pits, and reached individual cells. These facts may explain the origin and the formation mechanism of some silicified wood pieces in the strata of geological age. The silicified wood might be formed through the same mechanism with that recognized in this study within fairly short period of tens or hundreds of years.View full abstractDownload PDF (2000K) -
Mahito Watanabe, Makoto Miyake, Seiji Nozaki, Yasuo Yamamoto, Atsushi ...1999 Volume 105 Issue 2 Pages 116-121
Published: February 15, 1999
Released on J-STAGE: April 11, 2008
JOURNAL FREE ACCESSEarly to middle Miocene diatom fossils were found from the Bihoku Group in Koyamaichi area and the Katsuta Group in Tsuyama Area, Okayama Prefecture, southwest Japan. Ages of these two groups were determined based on the diatom assemblage of the groups. The upper part of the Bihoku Group in Koyamaichi area is assigned to the upper Crucidenticula kanayae Zone (NPD 3A, 16.9-16.3 Ma) and the lower Denticulopsis praelauta Zone (NPD 3B, 16.3-15.9 Ma). Diatom assemblage from one sample from the middle part of the Takakura Formation of the Katsuta Group in Tsuyama area is correlated to the upper C. kanayae Zone (NPD 3A, 16.9-16.3 Ma) or the lower D. praelauta Zone (NPD 3B, 16.3-15.9 Ma). These ages are older than the ages previously estimated based on foraminiferal biostratigraphy.View full abstractDownload PDF (1309K) -
Takashi Fujishiro, Tomoyoshi Kosaka1999 Volume 105 Issue 2 Pages 122-139
Published: February 15, 1999
Released on J-STAGE: April 11, 2008
JOURNAL FREE ACCESSThe stratigraphy and tectonics of the Neogene formations in the Shimonita Tectonic Zone extending along the northern margin of the Kanto Mountains are studied. The Lower Miocene formations distributed in the Shimonita Tectonic Zone are divided into the Kanohara Conglomerate, Iwayama Conglomerate and Kawai Sandstone and Mudstone Members in ascending order. The Kanohara Member is mostly composed of poorly-sorted boulder conglomerate consisting of reddish igneous rocks with Cretaceous age. The Iwayama Member is characterized by matrix-supported conglomerates having more compositional varieties of gravel than the underlying Kanohara Conglomerate Member. The Kawai Member conformably overlies the Iwayama Member and consists of sandy mudstone and sandstone. The Nukabe Formation which unconformably overlies the Shimonita Formation consists mainly of sandstone, mudstone and alternating beds of sandstone and mudstone. The Cenozoic formations in the Shimonita Tectonic Zone are separated into western and eastern area tectonically by the Sendaira-Maita Line. The formation of the western area is folded into the Shimonita Syncline, while the Nukabe Formation in the eastern area arched into open folds. On the basis of the geological, sedimentological and paleontological analysis, the lower two Members(the Kanohara and Iwayama Members) of the Shimonita Formation may have deposited in an alluvial fan environment. The Iwayama Member may have deposited in a shallow marine environment. The early Miocene shallow sea expanding in this area is designated the Paleo-Shimonita Bay.View full abstractDownload PDF (2050K) -
Takami Nobuhara, Ryoichi Takatori1999 Volume 105 Issue 2 Pages 140-150_1
Published: February 15, 1999
Released on J-STAGE: April 11, 2008
JOURNAL FREE ACCESSFossils of the seep-related bivalve Calyptogena sp. occur in alternating beds of turbiditic sandstone and siltstone in the Pliocene Horinouchi Formation of the Sagara-Kakegawa area, central Japan. The Horinouchi Formation consists of submarine fan deposits which filled the Plio-Pleistocene fore-arc basin formed by oblique subduction of the Philippine Sea Plate beneath the southwestern Honshu Arc. The Horinouchi Formation near the fossil locality interfingers with the Abina Formation, which consists of disorganized, angular pebble- to boulder-conglomerate distributed along the landward marginal fault of the basin.Calyptogena shells representing various growth stages occur at many horizons in a Horinouchi Formation sequence about 20 m thick consisting of alternating sandstone and siltstone. Most of the Calyptogena shells are disarticulated and buried in a convex-up position in the basal part of the sandstone beds, but some are articulated and present in the siltstone beds. These occurrences suggest that the Calyptogena habitat was continuously present on the landward slope during deposition of the 20-m-thick turbidite. This habitat may be related to the tectono-sedimentary settings characteristic of the landward margin of a fore-arc basin, such as marginal fault activity associated with basin subsidence, or related to high input of nutrient-rich organic matter by turbidity currents.On the basis of hinge characters, Calyptogena sp. from the Horinouchi Formation is distinct from the Calyptogena (s.l.) species reported from the Tamari and the Hijikata Formations, both of which consist of massive Pliocene siltstone present in the center of the same basin. The occurrences of different Calyptogena (s.l.) species reflect variations in habitat conditions for chemoautotrophic bivalves in a fore-arc basin.View full abstractDownload PDF (2414K) -
Chika Ito, Toshiaki Irizuki, Masao Iwai1999 Volume 105 Issue 2 Pages 152-155
Published: February 15, 1999
Released on J-STAGE: April 11, 2008
JOURNAL FREE ACCESSDiatom zonal key species are identified in the samples from the Morozaki (the Toyohama, Yamami and Utsumi Formations), Iwamura (the Toyama Formation) and Tomikusa (the Awano and Yonekawa Formations) Groups. These assemblages are characterized by the abundant occurrences of Kisseleviella carina and Stephanopyxis spp. The presence of Crucidenticula sawamurae, C. ikebei, Delphineis kamenooensis and D. miocenica, and the absence of Crucidenticula kanayae suggest that all of those samples from above groups are placed within the middle to upper part of C. sawamurae Zone (late Early Miocene).View full abstractDownload PDF (855K) -
Akira Ishiwatari1999 Volume 105 Issue 2 Pages 156-158
Published: February 15, 1999
Released on J-STAGE: April 11, 2008
JOURNAL FREE ACCESSDownload PDF (609K) -
Akira Ishiwatari, Tatsuki Tsujimori, Yasutaka Hayasaka, Takashi Sugimo ...1999 Volume 105 Issue 2 Pages III-IV
Published: 1999
Released on J-STAGE: November 26, 2010
JOURNAL FREE ACCESS
- |<
- <
- 1
- >
- >|