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Volume 105, Issue 10
Displaying 1-7 of 7 articles from this issue
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Gentaro Kawakami, Kohki Yoshida, Tadashi Usuki1999 Volume 105 Issue 10 Pages 673-686
Published: October 15, 1999
Released on J-STAGE: April 11, 2008
JOURNAL FREE ACCESSThe N-S trending trough basins developed in the Ishikari-Teshio Belt, central Hokkaido, were infilled by Middle Miocene coarse clastic sediments. According to former studies, the coarse clastics have been estimated to be derived from the northern part of Esashi-Hidaka Belt that was uplifted in relation to the collision events of the Amurian and Okhotsk Plates.In Hobetsu area located at the southern part of the Ishikari-Teshio Belt, the Kawabata Formation consists of turbidites and associated coarse clastics, and overlies the mudstone of the Takinoue Formation. The Kawabata Formation is characterized by monotonous alternating beds of sandstone and mudstone, and intercalated non-channelized, sheet-like coarse clastic deposits. Horizontally, coarsening eastward pattern is observed, but there are few facies changes along the basin axis. The facies and facies distribution pattern suggest that the Kawabata Formation was deposited in basin plain environment and coarse clastics were derived from the eastern hinterland through a slope area which developed at the basin margin.In addition, we recognized metamorphic rock fragments and detrital garnets derived from high grade metamorphic rocks (e.g. granulitic rocks originated from muddy sediments) in some sandstone of the Kawabata Formation. This fact suggests the Kamuikotan "tectonic" and Hidaka Metamorphic Belts, which are situated to the east of the Hobetsu area, are the most probable provenance.Although former studies regarded the northern part of the Esashi-Hidaka Belt as a provenance area of the Kawabata Formation, this study proposes the coexistence of the eastern hinterland located in the southern part of Esashi-Hidaka Belt which had been thought to be sea area during Middle Miocene time. It also suggests the earlier timing of uplifting of the Hidaka metamorphic rocks than the former studies.View full abstractDownload PDF (2339K) -
Kazuo Kamura, Hisashi Nirei1999 Volume 105 Issue 10 Pages 687-698
Published: October 15, 1999
Released on J-STAGE: April 11, 2008
JOURNAL FREE ACCESSWe have attempted to use the properties of resistivity of waste deposits in order to understand the actual conditions of landfills. The electric prospecting by Wenner method was carried out at three landfill sites in which the fill materials and their distribution were generally known. Furthermore the variations of apparent resistivities by electrical log and the conductivities of groundwater and seepage water were measured in the waste deposits. The above investigations were also performed in a site of surplus soil from construction works and a site filled with sand and silt. The general properties of resistivity of waste deposits from their data were extracted and relationships between the property and materials in the fills were examined.The following are the main results in the study.(1) The resistivities are a few ohm-m in waste deposits consisting mainly of ashes and tens ohm-m in reclaimed fills with sand and silt.(2) The conductivities of groundwater and seepage water in waste and surplus soil deposits are tens to hundreds times to those in fills with sand and silt, and reflects the resistivity of deposits.(3) The resistivity of rubber sheet to seal the water under the bottom of waste deposits is higher than that of the surrounding fill materials.(4) The resistivity of waste deposits can be a standard for considering the closure of the landfill site.View full abstractDownload PDF (1495K) -
Motoharu Kawano, Katsutoshi Tomita1999 Volume 105 Issue 10 Pages 699-710
Published: October 15, 1999
Released on J-STAGE: April 11, 2008
JOURNAL FREE ACCESSWeathering reactions of a rhyolitic pyroclastic flow deposit in southern Kyushu, Japan were investigated in order to understand the behavior of elements and the formation and evolution of reaction products. The weathering profile developed in the pyroclastics contains variable amounts of erionite, halloysite and noncrystalline Al-Si-Fe-rich materials with or without noncrystalline Mn-rich material as weathering products. The formation of these products appears to reach depth of more than 10 m below the surface. The mobility of cations in this profile is Na>Ca>K>Si>Fe>Al>Ti>Mn, in which Al, Fe, Mn, and Ti accumulate mostly in the surface horizon during the weathering. The accumulation of these elements is caused by dissolution of volcanic glass, feldspar, and pyroxene, and precipitation of noncrystalline clays enriched in Al, Fe, Mn, and Ti. Aluminum and Si released into solutions from volcanic glass and feldspar tend to combine with each other to produce Al-Si complexes with high reactivity with other metal cations at the initial weathering stages. Fe2+ and Mn2+ derived mainly from pyroxene are incorporated with the Al-Si complexes and precipitate as Al-Si materials containing Fe and Mn exhibiting irregular aggregates of randomly elongated very fine noncrystalline fibers less than 0.1μm in length. These noncrystalline fibers tend to crystallize to halloysite by partial development of a domain structure and elimination of Fe and Mn during crystallization processes. This weathering profile characteristically contains erionite crystals exhibiting hexagonal rods and thin needles normally less than 5μm in length as a major weathering product of the rhyolitic pyroclastic flow deposit. The chemical compositions of erionite crystals show a wide range with negative correlation between numbers of Si and those of Al+Fe3++Ti in which Si content increases continuously with depth. These erionite crystals may have been formed in a micro-environment where high pH and high cation activity conditions have been achieved by heterogeneous dissolution of volcanic glass and feldspar.View full abstractDownload PDF (2247K) -
Reishi Takashima, Hiroshi Nishi1999 Volume 105 Issue 10 Pages 711-728
Published: October 15, 1999
Released on J-STAGE: April 11, 2008
JOURNAL FREE ACCESSMany previous works on the Central Hokkaido support a tectonic model that exposure of Kamuikotan metamorphic belt occurred in the middle Cretaceous, and that the Yezo sedimentary basin was divided into the western and eastern terranes by the movement. The recognition of this event named as "the intra-Yezo disturbance" is based mainly on the exsitence of unconformity where basal conglomerates of "the Middle Yezo Group" (the middle part of Yezo Group) overlie alternating beds and limestones of "the Lower Yezo Group" (the lower part of Yezo Group).On the basis of lithology, sedimentary facies and microfossil biostratigraphy in both basal conglo-merate beds and the underlying strata, conglomerates and breccias distributed in the Soeushinai and Oyubari-Ashibetsu areas of the western terrane of the Yezo Group are recognized as debris flow deposits associated with felsic tuff beds which are correlated with the late Albian Maruyama Formation, the middle part of the Yezo Group. In the western Kanayama, southern Kanayama, Soshubetsu, Hidaka and Idonnappu areas of the eastern terrane, basal conglomerates reported by the previous workers are olistostromes or redeposited conglo-merates which belong to the lower part of the Yezo Group and are assigned to the late Aptian. Hence, coglomerate beds in previous works can be classified into the Aptian olistostromes and the late Albian debris flow deposits associated with tuff beds. These two deposits are distributed widely in both eastern and western terranes of the Yezo Group. These observations suggest that conglomerates assignable to "the intra-Yezo disturbance" are not typical basal conglomerates, and the uplifted model of Kamikotan ridge needs to be reviced. Instead, the extensive distributions of olistostromes and tuff beds in the Central Hokkaido indicate two mid-Cretaceous tectonic events which are huge submarine sliding in the late Aptian, and the following large-scale felsic volcanism in the late Albian.View full abstractDownload PDF (3276K) -
Jun-ichi Tazawa, Susumu Ando, Shinya Furuhashi, Kozue Furuta, Toshie O ...1999 Volume 105 Issue 10 Pages 729-732
Published: October 15, 1999
Released on J-STAGE: April 11, 2008
JOURNAL FREE ACCESSThe following four brachiopod species are newly recognized from the Okutadami area, central Japan : Anemonaria sp., Yokovlevia sp., Spiriferella sp. and Attenuatella sp. These brachiopods indicate a late Middle Permian (Midian) in age. The Okutadami fauna, consisting of both the Boreal- and Bipolar-type genera, is the first documented Permian Boreal brachiopod fauna in Japan. The occurrence of the Boreal brachiopod fauna from the Okutadami area suggests that the fossil-bearing rocks were formed at the northernmost part of Japan in the Permian time.View full abstractDownload PDF (920K) -
Fumio Akiba1999 Volume 105 Issue 10 Pages 733-736
Published: October 15, 1999
Released on J-STAGE: April 11, 2008
JOURNAL FREE ACCESSA diatom assemblage containing Neodenticula seminae and Proboscia curvirostris as well as numerous reworked specimens, is reported from a sample from the Yuchi Formation distributed in the Tenpoku area, northwestern Hokkaido. The formation has been generally regarded to be Pliocene in age on the basis of the occurrence of the molluscan Takikawa - Honbetsu Fauna and the recognition of the diatom "Denticulopsis seminae var. fossilis - D. kamtschatica" Zone. The occurrence of N. seminae suggests that the reported "D. seminae var. fossilis" in the formation may include both N. koizumii and N. seminae, and the finding of the Pleistocene species P. curvirostris implies that the formation is Pleistocene in age at least partially. The present result further indicates that other strata correlated to the Yuchi Formation in various areas of Hokkaido also need re-examination of their geologic ages in order to evaluate the timing of the youngest Cenozoic marine sedimentation in Hokkaido more precisely.View full abstractDownload PDF (773K) -
Kenta Kobayashi, Tatsuro Fukuchi, Noriko Hasebe, Aiming Lin, Tadashi M ...1999 Volume 105 Issue 10 Pages XIX-XX
Published: 1999
Released on J-STAGE: November 26, 2010
JOURNAL FREE ACCESS
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