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Featured researches published by Tetsuya Tokiwa.


Archive | 2017

Effectiveness for Determination of Depositional Age by Detrital Zircon U–Pb Age in the Cretaceous Shimanto Accretionary Complex of Japan

Tetsuya Tokiwa; Makoto Takeuchi; Yusuke Shimura; Akari Ota Kazuho Shobu; Koshi Yamamoto; Hiroshi Mori

Detrital zircon U–Pb ages indicate the crystallization age. Therefore, it is necessary to evaluate the effectiveness of determining the age of deposition using zircon age data. We carried out U–Pb dating of detrital zircons from sandstone at eight sites in the Cretaceous Shimanto accretionary complex on Kii Peninsula, Japan, with the aim of evaluating the accuracy of U–Pb zircon ages as indicators of the depositional age of sedimentary rocks by comparing zircon ages with radiolarian ages. Our results reveal zircons of late Cretaceous age, and the youngest peak ages are in good agreement with depositional ages inferred from radiolarian fossils. In addition, the youngest peak ages become younger as tectono-structurally downwards, and this tendency is clearer for the zircon ages than for the radiolarian ages. These results indicate that newly crystalized zircons were continuously supplied to the sediment by constant igneous activity during the late Cretaceous and that zircon ages provide remarkably useful information for determining the age of deposition in the Cretaceous Shimanto accretionary complex.


ASME 2010 13th International Conference on Environmental Remediation and Radioactive Waste Management, Volume 2 | 2010

An Attempt to Evaluate Horizontal Crustal Movement by Geodetic and Geological Approach in the Horonobe Area, Northern Hokkaido, Japan

Tetsuya Tokiwa; Koichi Asamori; Tadafumi Niizato; Tsuyoshi Nohara; Yuki Matsuura; Hideki Kosaka

In this study, we present the preliminary results for the estimation of a horizontal crustal movement by using geodetic and geological approach in the Horonobe area, northern Hokkaido, Japan. The estimations have been carried out by using a GPS data and a geological cross section obtained by applying balanced-section method. As results of this study, both of the shortening rates estimated by GPS data and balanced-section method indicate several millimeters per year. Namely, there is no contradiction between geodetic and geological data, and it is considered that Horonobe area is still situated similar tendency and magnitude of a crustal movement. It is seemingly considered that geodetic data is unhelpful for estimating the long-term crustal movement, because period of geodetic observations is a very short. However, the result of this study indicates that geodetic data provide valuable information for estimating the long-term crustal movement in the area, and it is considered that geodetic approach play an important role in improvement of the credibility of evaluation for prediction of long-term stability.Copyright


ASME 2010 13th International Conference on Environmental Remediation and Radioactive Waste Management, Volume 2 | 2010

Relationship Between Hypocentral Distribution and Geological Structure in the Horonobe Area, Northern Hokkaido, Japan

Tetsuya Tokiwa; Koichi Asamori; Naoto Hiraga; Osamu Yamada; Hirokazu Moriya; Hikaru Hotta; Itaru Kitamura; Hideharu Yokota

In this paper, we discuss the relationship between the accurate hypocentral distribution and three-dimensional (3-D) geological structure in and around the Horonobe area in northern Hokkaido, Japan. The multiplet-clustering analysis was applied to the 421 micro-earthquakes which occurred from 1 September, 2003 to 30 September, 2007. The 3-D geological structure model was mainly constructed from previous seismic reflection profiles and borehole data. As a result of this analysis, although with slight differences in depth between them, the hypocenters were found to be distributed in the NNW-SSE direction and become deeper from the west toward the east. The distributed pattern of the hypocenters is similar to that of the geological structure. These results indicate that the hypocentral distribution may represent existence of active zone related to the geological structure, and provide effective information which can contribute to establishing methods for estimating the future evolution of the geological environment.


Journal of Asian Earth Sciences | 2009

Upper Silurian and Devonian pelagic deep-water radiolarian chert from the Khangai–Khentei belt of Central Mongolia: Evidence for Middle Paleozoic subduction–accretion activity in the Central Asian Orogenic Belt

Toshiyuki Kurihara; Kazuhiro Tsukada; Shigeru Otoh; Kenji Kashiwagi; Minjin Chuluun; Dorjsuren Byambadash; Bujinlkham Boijir; Sersmaa Gonchigdorj; Manchuk Nuramkhan; Masakazu Niwa; Tetsuya Tokiwa; Gen’ya Hikichi; Takafumi Kozuka


Journal of Structural Geology | 2010

Relationship between fault growth mechanism and permeability variations with depth of siliceous mudstones in northern Hokkaido, Japan

Eiichi Ishii; Hironori Funaki; Tetsuya Tokiwa; Kunio Ota


Island Arc | 2009

Timing of dextral oblique subduction along the eastern margin of the Asian continent in the Late Cretaceous: Evidence from the accretionary complex of the Shimanto Belt in the Kii Peninsula, Southwest Japan

Tetsuya Tokiwa


Sedimentary Geology | 2007

Changes in detrital garnet assemblages related to transpressive uplifting associated with strike–slip faulting: An example from the Cretaceous System in Kii Peninsula, Southwest Japan

Kyaw Soe Win; Makoto Takeuchi; Tetsuya Tokiwa


International Journal of Rock Mechanics and Mining Sciences | 2011

Influence of a fault system on rock mass response to shaft excavation in soft sedimentary rock, Horonobe area, northern Japan

Tetsuya Tokiwa; Kimikazu Tsusaka; Eiichi Ishii; Hiroyuki Sanada; Eiji Tominaga; Yoshihiro Hatsuyama; Hironori Funaki


Island Arc | 2013

Geological setting of basaltic rocks in an accretionary complex, Khangai–Khentei Belt, Mongolia

Kazuhiro Tsukada; Yuki Nakane; Koshi Yamamoto; Toshiyuki Kurihara; Shigeru Otoh; Kenji Kashiwagi; Minjin Chuluun; Sersmaa Gonchigdorj; Manchuk Nuramkhaan; Masakazu Niwa; Tetsuya Tokiwa


Journal of the Geological Society of Japan | 2015

Redefinition of the Cretaceous terrigenous strata in the northeastern Toyama Prefecture based on U-Pb ages of zircon

Makoto Takeuchi; Masahiro Ohkawa; Kentaro Kawahara; Satoru Tomita; Hideharu Yokota; Tetsuya Tokiwa; Ryuta Furukawa

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Kimikazu Tsusaka

Japan Atomic Energy Agency

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Kazuhei Aoyagi

Japan Atomic Energy Agency

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Hideharu Yokota

Japan Atomic Energy Agency

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Daisuke Inagaki

Japan Atomic Energy Agency

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