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Journal Articles

Fluvial sediments and porcelain clay of the Miocene to Pleistocene Seto Group, central Japan

Hatano, Nozomi*; Yoshida, Koki*; Sasao, Eiji

Chishitsugaku Zasshi, 127(6), p.345 - 362, 2021/06

This paper is guidebook of field excursion at the 127th annual meeting of the Geological Society of Japan, originally planned to be held on September, 2020 (postponed for one year). Miocene to Pleistocene Seto Group yields porcelain clay and are studied in the point of view of clay mineralogy and geology. In this field excursion, genesis of porcelain clay will be discussed through the observation of paleosols, paleoweathering profiles of the Seto Group and the basement strongly weathered granite.

Journal Articles

Dating of a fault zone distributed in the South Kyushu shear zone based on fission-track thermochronology and U-Pb dating

Sueoka, Shigeru; Shimada, Koji; Terusawa, Shuji*; Iwano, Hideki*; Danhara, Toru*; Ogita, Yasuhiro; Hirata, Takafumi*

Chishitsugaku Zasshi, 127(1), p.25 - 39, 2021/01

no abstracts in English

Journal Articles

K-Ar ages of an andesitic parallel dike swarm in the Takane area, Takayama City, Gifu Prefecture, Central Japan

Niwa, Masakazu; Ueki, Tadamasa*; Hoshi, Hiroyuki*; Sugisaki, Yuichi*; Yagi, Koshi*; Tozawa, Terumasa

Chishitsugaku Zasshi, 126(9), p.543 - 548, 2020/09

A large number of paleomagnetic and chronological studies have contributed to the elucidation of the early Miocene clockwise rotation of Southwest Japan associated with the major opening of back-arc basins of the Japan Sea. Paleomagnetic data from an andesitic parallel dike swarm in the Takane area, Takayama City, Gifu Prefecture, Central Japan, were previously reported, showing the easterly deflection of the observed magnetization direction compared to an early Miocene expected paleomagnetic direction. This must represent the clockwise rotation during the opening of the Japan Sea, if the dike swarm was intruded before the opening event. Here, we report new K-Ar hornblende ages from an andesite dike of the dike swarm. These ages are statistically indistinguishable, indicating emplacement of the dike swarm before the clockwise rotation.

Journal Articles

Zircon U-Pb and fission-track ages for tephra interbedded in Neogene and Quaternary in Horonobe area, northern Hokkaido

Niwa, Masakazu; Amamiya, Hiroki*; Yonaga, Yusuke; Ogita, Yasuhiro; Yasue, Kenichi*; Iwano, Hideki*; Danhara, Toru*; Hirata, Takafumi*

Chishitsugaku Zasshi, 126(5), p.267 - 283, 2020/05

U-Pb and fission-track (FT) ages from single zircon grain were measured for three tephra samples (TKB3, TKB6, and TKB7) intercalated in Neogene to Quaternary in Horonobe area, Hokkaido, to understand their depositional ages. In TKB3 and TKB6, weighed average U-Pb and FT ages for zircon grains within the youngest age range are coincident within a range of error 2 $$sigma$$ each other, which suggest that their ages correspond to the eruption ages. In TKB7, FT ages for most zircons are reset to their U-Pb ages or younger. The weighed average FT age for all analyzed zircons and weighed average U-Pb age for zircon grains within the youngest age range are coincident within a range of error 2 $$sigma$$ each other. Thus, their ages could also show the eruption age.

Journal Articles

Zircon U-Pb and Fission-track ages for the Ohta Tephra in the Pliocene Tokai Group, Central Japan

Ueki, Tadamasa; Niwa, Masakazu; Iwano, Hideki*; Danhara, Toru*; Hirata, Takafumi*

Chishitsugaku Zasshi, 125(3), p.227 - 236, 2019/03

no abstracts in English

Journal Articles

Zircon U-Pb and reassessed zircon fission track ages of Miocene Mizunami and Iwamura Groups in the southeastern part of Gifu Prefecture, central Japan

Sasao, Eiji; Danhara, Toru*; Iwano, Hideki*; Hirata, Takafumi*

Chishitsugaku Zasshi, 124(2), p.141 - 150, 2018/02

Here U-Pb and reassessed fission track (FT) ages are presented for samples from the Miocene Mizunami and Iwamura groups in the southeastern Gifu Prefecture, central Japan. The U-Pb ages of three tuff samples coincide with the reassessed FT ages within the error range. These new U-Pb and reassessed FT ages are consistent with those reported in previous microfossil and paleomagnetic studies, which indicate the following depositional history: The Hongo and Akeyo formations of the Mizunami Group were deposited at ~19-18 Ma and ca. 18 Ma, respectively, and the lower part of the Toyama Formation of the Iwamura Group was deposited ca. 18 Ma.

Journal Articles

Modal analysis using scanning X-ray analytical microscope and image processing and analyzing softwares

Ueki, Tadamasa; Niwa, Masakazu

Chishitsugaku Zasshi, 123(12), p.1061 - 1066, 2017/12

Conventional point counting method for modal analysis is time-consuming, and often affected by measurer's skill and subjective view on the determination of minerals. We introduce the alternate method using scanning X-ray analytical microscope and image processing and analyzing softwares. This method is simple and not affected by measurer's skill and subjective view. By using this method for thin sections or polished slabs of granitic rocks, we provided clear images showing mineral distributions and obtained objective data of modal compositions efficiently and quickly.

Journal Articles

Identification of pumice derived from historic eruption in the same volcano; Case study for the Sakurajima-Bunmei tephra in the Miyazaki Plain

Ikuta, Masafumi*; Niwa, Masakazu; Danhara, Toru*; Yamashita, Toru*; Maruyama, Seiji*; Kamataki, Takanobu*; Kobayashi, Tetsuo*; Kurosawa, Hideki*; Kokubu, Yoko; Hirata, Takafumi*

Chishitsugaku Zasshi, 122(3), p.89 - 107, 2016/03

We carried out mineral composition analysis, morphological classification of volcanic glass shards and refractive index measurements of the glass shards and orthopyroxene from the eruption products from Sakurajima volcano. In this study, refractive indexes of hydrated and non-hydrated parts within each individual glass shard were measured separately. This measurements in consideration of hydration in glass shards made possible distinct discrimination of the pumice samples from the three eruption events of Bunmei, An-ei, and Taisho. Pumice layers in the core samples obtained from the southern part of the Miyazaki Plain were also identified as the Sakurajima-Bunmei tephra by the above mentioned analyses, and also by the data of radiocarbon dating for coaly materials included in the pumice layers. Occurrences of the pumice layers suggest that the Sakurajima-Bunmei tephra could have reached the southern part of Miyazaki Plain as pumice falls.

Journal Articles

Study on index of erosion rate in inland mountains; Case study using old river valley around detached meander core

Yasue, Kenichi; Takatori, Ryoichi*; Tanikawa, Shinichi*; Ninomiya, Atsushi*; Tanase, Atsushi*; Furusawa, Akira*; Tajikara, Masayoshi*

Chishitsugaku Zasshi, 120(12), p.435 - 445, 2014/12

Estimating the rate of change in landforms and geological environments due to erosion is important when assessing the safety of the geological disposal of high-level radioactive waste in Japan. The aim of this study is to develop an index of erosion rates in inland mountains. We focused on circular abandoned channels, which are old river valleys around detached meander cores formed by the cut-off of incised meandering rivers. The channels can be useful for estimating incision rates because they occur at a range of elevations throughout the Japanese Islands. We undertook a case study to determine the incision rate using a circular abandoned channel in the middle reaches of the Kumanogawa River in the Kii Peninsula, where many circular abandoned channels have been identified. We obtained undisturbed core samples of old river channel deposits and angular gravel deposits that overlie the circular abandoned channel. The old river channel deposits have been emergent since at least MIS5, based on an analysis of the soil color in angular gravel deposits. The incision rate, as calculated from this age and the difference in elevation between the abandoned and present channels, is less than about 0.9 m/ky. This study shows that analyses of circular abandoned channels can yield estimates of incision rates and potentially also uplift rates. More accurate estimates of incision rates require further studies of the dating and evolution of sediments that overlie circular abandoned channels.

Journal Articles

Subsurface geological mapping of the Japanese islands

Yasue, Kenichi; Ishimaru, Tsuneari; Kobori, Kazuo; Umeda, Koji; Nakatsuka, Noboru

Chishitsugaku Zasshi, 120(12), p.XIII - XIV, 2014/12

From the viewpoint of present and future use of underground space such as the geological disposal of radioactive waste and carbon dioxide, this is a need to understand subsurface geological structures in the Japanese islands. In general, conventional methods of subsurface mapping are widely used to convert subsurface geological information into two-dimensional space. We present subsurface geological structures on horizontal-section maps at depths of 0, 500, and 1,000 meters below sea level. We also map surface geological units consisting of pre-Neogene basement rocks. Data from existing geological maps, geological cross sections and boreholes were used as input to the maps. The data has been gathered from publications prior to 2001.

Journal Articles

Long-term stability and function as a natural barrier of various geological environments in Japan from the perspective of uranium deposits

Sasao, Eiji

Chishitsugaku Zasshi, 120(10), p.345 - 359, 2014/10

This study utilizes information on the uranium deposit as an analogue of the long-term stability and function as the natural barrier system of the geological environments in Japanese island. Information on distribution and mode of occurrence of uranium deposit was compiled from the published data. Distribution of uranium deposit suggests that geological environments suitable for geological isolation are widely distributed in the Japanese Islands, despite their location in a geologically active area. The mode of occurrence of the uranium deposits indicates that formation of uranium-bearing mineral as well as sorption is expected in both sedimentary and crystalline rocks. The functioning of the natural barrier would be expected in various geological environments in the Japanese Islands, because mineralization and sorption are regarded as a barrier function to retard the migration of radionuclides in HLW, and because of the uranium deposits in the various rock types.

Journal Articles

A Sampling method of oriented small sample from fault cores for SEM observation

Shimada, Koji; Kametaka, Masao*; Nakayama, Kazuhiko; Seshimo, Kazuyoshi; Tanaka, Yoshihiro; Hayashi, Toshio*; Tanaka, Yukumo; Shimogama, Kota*; Okazaki, Kazuhiko*

Chishitsugaku Zasshi, 119(11), p.727 - 731, 2013/11

Staples for a stapler can be used as a frame of a small oriented sample taken from fragile and scarce fault gouge. The fault gouge was slotted for staples of an insert. Staples are a group of about ten or less ones holding right-angled three small surfaces. Pre-oriented staples set the slot would remove then presented for the SEM observation. Only a knife, some glues and simple equipment are needed for the method in the field or laboratories.

Journal Articles

Geological investigations for geological model of deep underground geoenvironment at the Mizunami Underground Research Laboratory (MIU)

Tsuruta, Tadahiko; Tagami, Masahiko; Amano, Kenji; Matsuoka, Toshiyuki; Kurihara, Arata; Yamada, Yasuhiro*; Koike, Katsuaki*

Chishitsugaku Zasshi, 119(2), p.59 - 74, 2013/02

Japan Atomic Energy Agency (JAEA) is developing a geoscientific research project, Mizunami Underground Research Laboratory (MIU) project, in order to establish scientific and technological basis for geological disposal of HLW. A series of geological mapping, reflection seismic survey, borehole investigation and geological investigations around research galleries are carried out to identify the distribution and the heterogeneity of fractures and faults that are potential major flow-pass of groundwater as field investigations. This paper describes geological investigations in the MIU project, focused on the evaluation of their effectiveness in order to understand the deep underground geological environment.

Journal Articles

Thermochronological study of the dip-slip displacement and timing of initiation of the Atera fault

Yamada, Kunimi; Yasue, Kenichi; Iwano, Hideki*; Yamada, Ryuji*; Umeda, Koji; Omura, Kentaro*

Chishitsugaku Zasshi, 118(7), p.437 - 448, 2012/07

Fission-track analyses for samples corrected from around the Atera fault indicated 2 conclusions. The dip-slip displacement of the Atera fault after Cretaceous is about 1 km. It is similar to the displacement of basement rocks or topography across the fault. These are consistent with previous studies that indicated the present Atera fault activity began after late Pliocene. The fracture zone along the fault was widely heated at about 20 Ma. It indicates that the fracture zone existed at the time and perhaps the paleo fault activity has already begun.

Journal Articles

Fission track ages of the Miocene Mizunami and Iwamura Groups in southeastern Gifu Prefecture, central Japan

Sasao, Eiji; Danhara, Toru*; Iwano, Hideki*; Hayashi, Joji*

Chishitsugaku Zasshi, 117(8), p.476 - 481, 2011/08

Fission track age dating was done on 14 tuff samples from the Miocene Mizunami and Iwamura Groups, distributed in the southeastern part of Gifu Prefecture, central Japan. The depositional ages are estimated to be as follows: about 17 Ma (the Hongo Formation) and 17-16 Ma (the Akeyo Formation) for the Mizunami Group, 20-18 Ma (the Agi Formation) and 17-16 Ma (the middle part of the Toyama Formation) for the Iwamura Group. In terms of correlation of the Mizunami and Iwamura Groups and the Kani Group on the west side of the Mizunami Group, the Akeyo and Hongo Formations of the Mizunami Group correlate with the Toyama Formation of the Iwamura Group and the Hiramaki Formation of the Kani Group, respectively.

Journal Articles

Crush zone structure in a compressional step; An Example of the western part of the Atotsugawa Fault, Hida City, Gifu Prefecture of Japan

Niwa, Masakazu; Shimada, Koji; Kurosawa, Hideki; Miwa, Atsushi*

Chishitsugaku Zasshi, 114(10), p.495 - 515, 2008/10

This paper provides a geological description of crush zones in the western part of the active Atotsugawa Fault, Gifu Prefecture of Japan, to understand crush zone structures in steps of strike-slip faults. By means of aerial photograph interpretation, we recognized that the occurrence of a step is suggestive in the Sangawara area, and that a long strand of the Atotsugawa Fault with ENE-WSW trend is traced in the Itani Area. On the Basis of the detailed geological observation, attitude and sense of shear planes, and thickness and clay mineral composition of fault gouge are different between crush zones of the Sangawara and Itani areas. In the Sangawara area, shear planes with NNE-SSW and NW-SE strikes, high-angle oblique to the trend of the Atotsugawa Fault, are characteristically developed. These shear planes can be a part of the composite planar fabric such as R2 surfaces which are dominantly developed within compressional steps.

Journal Articles

Estimation of the paleostress field from the 3-D orientation distribution of microcracks and their geothermal conditions in the Toki Granite, central Japan

Takagi, Hideo*; Miwa, Shigenori*; Yokomizo, Yoshiyuki*; Nishijima, Kei*; Enjoji, Mamoru*; Mizuno, Takashi; Amano, Kenji

Chishitsugaku Zasshi, 114(7), p.321 - 335, 2008/07

Based on the 3-D orientations of intracrystalline healed, sealed and open extension microcracks in quartz grains in the Late Cretaceous Toki Granite, we discuss the paleostress field and the history of microcracking combining the microthermometry of fluid inclusions in healed microcracks and sealing material identification in sealed microcracks. Twenty one oriented samples are collected mainly from the DH-15 core (240-1000 mabh) drilled by Japan Atomic Energy Agency (JAEA) and additionally from five outcrops in the Tono region. 3-D orientations of healed microcracks indicate the $$sigma$$$$_{rm Hmax}$$ orientation of N-S to NW-SE in almost all sites, whereas those of sealed and open microcracks indicate the dominant $$sigma$$$$_{rm Hmax}$$ orientation of E-W. Two or three orthogonal sets of microcracks are common in both healed and sealed microcracks. The formation of these sets can be attributed to the switch of principal stress axis due to stress release just after the crack formation. Healed microcracks probably reflect more regional paleostress field because of consistency of the orientations than the case of sealed and open microcracks that show rather scattering orientations. N-S to NW-SE trending healed microcracks are formed around 60 Ma on the basis of K-Ar biotite ages of the Toki Granite and formation temperature (c. 300-400$$^{circ}$$C) of fluid inclusions estimated from microthermometry in the case of intrusion depth (3.5 km=100 MPa) of the Toki Granite. Thus the $$sigma$$$$_{rm Hmax}$$ orientation trended NW-SE after the restoration of clockwise rotation of SW Japan at c. 15 Ma. Following the healed microcrack formation, E-W trending high-angle sealed microcracks filled with carbonate mineral are formed. Open microcracks presumably formed at near-surface at the last stage of sealed microcrack formation after c. 20 Ma before the Mizunami Group deposited unconformably on the granite.

Journal Articles

Inception of anticline growth near the Omagari Fault, northern Hokkaido, Japan

Ishii, Eiichi; Yasue, Kenichi; Ohira, Hiroto*; Furusawa, Akira*; Hasegawa, Takeshi*; Nakagawa, Mitsuhiro*

Chishitsugaku Zasshi, 114(6), p.286 - 299, 2008/06

no abstracts in English

Journal Articles

Paleogeography and geological evolution since the Late Pliocene in and around the Horonobe area, northern Hokkaido

Niizato, Tadafumi; Funaki, Hironori; Yasue, Kenichi

Chishitsugaku Zasshi, 113(Suppl.), p.119 - 135, 2007/09

The tectonic framework in the northern part of Hokkaido has been controlled by interrelationship between the Amurian Plate and Okhotsk Plate since the Late Pliocene. The developments of the geological structure of fold-and-thrust belt with westward vergence and migration of depositional axis from east to west have been progressed in the framework since Late Pliocene. On the basis of distribution of fossil-periglacial phenomena and its origin, northern part of Hokkaido was located in the southern margin of the continuous permafrost zone or the northern margin of the discontinuous zone during the Last Glacial Maximum. This field trip includes the minor deformation structures and sedimentary facies developed in the Tertiary to Quaternary sedimentary formations, aeolian deposits from MIS7 to MIS5e, periglacial deposits in the LGM. It also includes the periglacial landform distributed in the Horonobe area.

Journal Articles

Change in groundwater pH by infiltration of meteoric water into shallow part of marine deposits

Ishii, Eiichi; Hama, Katsuhiro; Kunimaru, Takanori; Sato, Haruo

Chishitsugaku Zasshi, 113(2), p.41 - 52, 2007/02

In order to research water-rock interaction contributing to pH of groundwater in Neogene marine deposits in Horonobe area, northern Hokkaido, Japan, petrological and hydro-geochemical characteristics were investigated. As a result of the investigation, the following were shown. Leaching of Na from rocks occurs at infiltration zone of meteoric water of shallow part of the deposits, and the leaching is caused mainly by cation exchange reaction between Na$$^{+}$$ in smectite and H$$^{+}$$ in groundwater. The pH of groundwater in the shallow part is controlled mainly by the above cation exchange reaction. The pH increases when meteoric water infiltrates into the rocks, and decreases when saline water re-fills the rocks.

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