Updated on 2022/05/25

写真a

 
OHTA, Tohru
 
Affiliation
Faculty of Education and Integrated Arts and Sciences, School of Education
Job title
Professor

Concurrent Post

  • Faculty of Science and Engineering   Graduate School of Creative Science and Engineering

Research Institute

  • 2020
    -
    2022

    理工学術院総合研究所   兼任研究員

Education

  •  
    -
    2004

    Waseda University   Graduate school of Science and Engineering   Environment, Resources and Materials Science Engineering  

  •  
    -
    2004

    Waseda University   Graduate school of Science and Engineering   Environment, Resources and Materials Science Engineering  

  •  
    -
    2000

    Kyushu University   Faculty of Science   Earth and Planetary Sciences  

Degree

  • Waseda University   Doctor (Science)

Research Experience

  • 2013
     
     

    : Part-time lecturer of Graduate School of Chiba university

  • 2012
    -
     

    : Associate Professor of Waseda University

  • 2008
    -
    2011

    : Assistant professor at School of Education, Waseda University

  • 2005
    -
    2007

    : Research associate at School of Education, Waseda University

  • 2004
    -
    2005

    :Visiting researcher at Advanced Research Institute for Science and Engineering, Waseda University

Professional Memberships

  •  
     
     

    Geological Society of Japan

  •  
     
     

    Sedimenlotogical Society of Japan

  •  
     
     

    Japan Society of Geoinformatics

  •  
     
     

    Geochemical Society of Japan

  •  
     
     

    Japan Association of Mineralogical Sciences

  •  
     
     

    International Association of Sedimentologists

  •  
     
     

    Japan Geoscience Union

  •  
     
     

    American Geophysical Union

▼display all

 

Research Areas

  • Solid earth sciences

Research Interests

  • Basin analysis, Sedimentary gravity flow, Sandstone composition, Logratio analysis

Papers

  • Depositional ages and characteristics of Middle–Upper Jurassic and Lower Cretaceous lacustrine deposits in southeastern Mongolia

    Hitoshi Hasegawa, Hisao Ando, Noriko Hasebe, Niiden Ichinnorov, Tohru Ohta, Takashi Hasegawa, Masanobu Yamamoto, Gang Li, Bat-Orshikh Erdenetsogt, Ulrich Heimhofer, Takayuki Murata, Hironori Shinya, G. Enerel, G. Oyunjargal, O. Munkhtsetseg, Noriyuki Suzuki, Tomohisa Irino, Koshi Yamamoto

    Island Arc   27 ( 3 )  2018.05

     View Summary

    Lower Cretaceous lacustrine oil shales are widely distributed in southeastern Mongolia. Due to the high organic carbon content of oil shale, many geochemical studies and petroleum exploration have been conducted. Although most of the oil shales are considered to be Early Cretaceous in age, a recent study reveals that some were deposited in the Middle Jurassic. The present study aims at establishing depositional ages and characteristics of the Jurassic and Cretaceous lacustrine deposits in Mongolia. The Lower Cretaceous Shinekhudag Formation is about 250 m thick and composed of alternating beds of shale and dolomite. The Middle Jurassic Eedemt Formation is about 150 m thick and composed of alternating beds of shale, dolomitic marl, and siltstone. The alternations of shale and dolomite in both formations were formed by lake level changes, reflecting precipitation changes. Shales were deposited in the center of a deep lake during highstand, while dolomites were formed by primary precipitation during lowstand. Based on the radiometric age dating, the Shinekhudag Formation was deposited between 123.8 ±2.0 Ma and 118.5 ±0.9 Ma of the early Aptian. The Eedemt Formation was deposited at around 165–158 Ma of Callovian–Oxfordian. The calculated sedimentation rate of the Shinekhudag Formation is between 4.7 ±2.6 cm/ky and 10.0 ±7.6 cm/ky. Shales in the Shinekhudag Formation show micrometer-scale lamination, consisting of algal organic matter and detrital clay mineral couplets. Given the average thickness of micro-laminae and calculated sedimentation rate, the micro-lamination is most likely of varve origin. Both Middle–Upper Jurassic and Lower Cretaceous lacustrine oil shales were deposited in intracontinental basins in the paleo-Asian continent. Tectonic processes and basin evolution basically controlled the deposition of these oil shales. In addition, enhanced precipitation under humid climate during the early Aptian and the Callovian–Oxfordian was another key factor inducing the widespread oil shale deposition in Mongolia.

    DOI

  • Sedimentation history of the Paleoproterozoic Singhbhum Group of rocks, eastern India and its implications

    Shuvabrata De, Leena Mallik, Rajat Mazumder, Priyanka Chatterjee, Tohru Ohta, Satoshi Saito, Jeff Chiarenzelli

    EARTH-SCIENCE REVIEWS   163   141 - 161  2016.12  [Refereed]

     View Summary

    This paper reviews the sedimentological, geochemical and stratigraphic characteristics of the Paleoproterozoic Chaibasa and Dhalbhum Formations (the Singhbhum Group) of eastern India and presents a comparative study with other Paleoproterozoic lithostratigraphic units of India. Both the formations are entirely siliciclastic and deformed and metamorphosed, generally at greenschist to upper amphibolite facies. The older Chaibasa Formation consists of sandstone, shale and sandstone-shale interbanded (heterolithic) facies. It conformably over-lies the Late Archean-Paleoproterozoic Dhanjori Formation of terrestrial (alluvial fan-fluvial) origin. The Lower Chaibasa Member formed in a marine setting; the shale and heterolithic facies formed in a continental shelf setting below and above the storm wave base, respectively. The sandstone fades formed in a subtidal setting during sea level fall. In contrast, the Upper Chaibasa Member formed in a shallow-marine setting; both the shale and heterolithic facies formed above the storm wave base.
    In significant contrast, the overlying Dhalbhum Formation is dominated by finer clastics with much lower proportion of sandstones. The base of the terrestrial Dhalbhum Formation is a sequence boundary (unconformity). Sedimentary facies analysis clearly shows two broad facies association of terrestrial origin (fluvial and aeolian). The aeolian facies association overlies the fluvial facies association. The Dhalbhum sandstones show typical REE pattern of quartz dilution with lower concentrations compared to the mudstones. The Dhalbhum finer clastics mimic typical REE patterns resembling abundances in the continental crust. Rare earth element plots display a good match with Post-Archean Australian Shales (PAAS) including similar concentrations, steep negative slope for LREEs, negative Eu anomaly, and nearly flat HREES. The Singhbhum Paleoproterozoic succession is devoid of both chemical sediments and Paleoproterozoic glacial deposits in contrast to neighboring cratons. (C) 2016 Elsevier B.V. All rights reserved.

    DOI

  • Morphology and phylogenetic origin of the spinicaudatan Neodiestheria from the Lower Cretaceous Dalazi Formation, Yanji Basin, north-eastern China

    Gang Li, Tohru Ohta, David J. Batten, Takashi Sakai, Takeshi Kozai

    CRETACEOUS RESEARCH   62   183 - 193  2016.07  [Refereed]

     View Summary

    The spinicaudatan Neodiestheria Chen is an important component of the diverse Early Cretaceous Yanjiestheria fauna in eastern Asia. Examination under a scanning electron microscope of newly collected and well-preserved specimens of Neodiestheria dalaziensis Chen from the Albian Dalazi Formation of Zhixin, Jilin Province, north-eastern China, has revealed morphological features of the carapace not recognized previously, namely that puncta are not only evenly distributed on growth bands near the umbo and gradually merge into a punctate fine reticulation and dense radial lirae on each growth band in the upper-middle part of the carapace, but also occur on growth lines and within the lumina of a fine reticulum, and between radial lirae on growth bands in the middle and lower parts of the carapace. Growth bands in anteroventral, ventral and posteroventral parts of the carapace are also ornamented with transversely elongate large pits (depressions) surrounded by swellings, appearing as a large reticulum superimposed over fine reticulation and radial lirae. These ontogenetically developing morphological patterns on the growth bands of the juvenile stage of the carapace indicate that Neodiestheria is closely related phylogenetically to Triglypta Wang. (C) 2015 Elsevier Ltd. All rights reserved.

    DOI

  • Provenance analysis of clastic sediments of the Shimanto Belts in Mie Prefecture using sandstone modal and whole-rock chemical compositions

    Kuzuhara Kouki, Ohta Tohru

    Annual Meeting of the Geological Society of Japan   2016 ( 0 )  2016

    CiNii

  • Paleoenvironmental analysis of the Mesozoic sections in Xinjiang-Uighur region, NW China : Paleoclimatic changes triggered by continental collision

    Uchikado Ryo, Ohta Tohru, Li Gang

    Annual Meeting of the Geological Society of Japan   2016 ( 0 )  2016

    CiNii

  • Characterization of submarine canyon bathymetries in northern Ionian Sea, Italy, using sediment geochemical variation induced by transportation distance and basin depth (vol 104, pg 1353, 2015)

    Francesco Perri, Tohru Ohta, Salvatore Critelli

    INTERNATIONAL JOURNAL OF EARTH SCIENCES   104 ( 7 ) 1907 - 1907  2015.10  [Refereed]

    DOI

  • Characterization of submarine canyon bathymetries in northern Ionian Sea, Italy, using sediment geochemical variation induced by transportation distance and basin depth

    Perri Francesco, Ohta Tohru, Critelli Salvatore

    INTERNATIONAL JOURNAL OF EARTH SCIENCES   104 ( 5 ) 1353 - 1364  2015.07  [Refereed]

     View Summary

    Geochemical data of marine mud sediments collected from the Esaro, Neto and Corigliano canyons in the northern Ionian Sea (southern Italy) were investigated in order to characterize canyon bathymetry types. Mud sample compositions analyzed by the principal component analysis (PCA) provided useful information for the morphology of the depositional area of the northern Ionian Sea. The use of sediment geochemical data as well as transportation distance and depth as input variables for PCA enabled the extraction of following latent variables: basin depth (PC1), sedimentation rate (PC2) and transportation distance (PC3). Based on these results, we further developed geochemical indices that can estimate basin depth (F1), sedimentation rate (F2) and transportation distance (F3); these functions can be solely calculated from the elemental concentration data of the mud samples. Since these F1, F2 and F3 functions are mathematically independent variables, they facilitate more precise characterization of individual canyon types. That is, the Esaro Canyon is regarded as a sediment-starved deep canyon characterized by a single source area; the Neto Canyon can be seen as a deeply sloped submarine apron system and sediments are mainly supplied by the sediment gravity flows; the Corigliano Canyon is characterized by multiple sources and moderately sloped system, whose sediments disperse mainly by traction currents. These interpretations are concordant with the basin bathymetry of the studied area. Therefore, F1, F2 and F3 functions might be applicable to any oceanic basins.

    DOI

  • Future lunar mission Active X-ray Spectrometer development: Surface roughness and geometry studies

    M. Naito, N. Hasebe, H. Kusano, H. Nagaoka, M. Kuwako, Y. Oyama, E. Shibamura, Y. Amano, T. Ohta, K. J. Kim, J. A. M. Lopes

    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT   788   182 - 187  2015.07  [Refereed]

     View Summary

    The Active X-ray Spectrometer (AXS) is considered as one of the scientific payload candidates for a future Japanese mission, SELENE-2. The AXS consists of pyroelectric X-ray generators and a Silicon Drift Detector to conduct X-Ray Fluorescence spectroscopy (XRF) on the Moon to measure major elements: Mg, Al, Si, Ca, Ti, and Fe; minor elements: Na, K, F, S, Cr and Mn; and the trace element Ni depending on their concentration. Some factors such as roughness, grain size and porosity of sample, and the geometry of X-ray incidence, emission and energy will affect the XRF measurements precision. Basic studies on the XRF are required to develop the AXS. In this study, fused samples were used to make homogeneous samples free from the effect of grain size and porosity. Experimental and numerical studies on the XRF were conducted to evaluate the effects from incidence and emission angles and surface roughness. Angle geometry and surface roughness will be optimized for the design of the AXS on future missions from the results of the experiment and the numerical simulation. (C) 2015 Elsevier B.V. All rights reserved.

    DOI

  • Future lunar mission Active X-ray Spectrometer development: Surface roughness and geometry studies

    M. Naito, N. Hasebe, H. Kusano, H. Nagaoka, M. Kuwako, Y. Oyama, E. Shibamura, Y. Amano, T. Ohta, K. J. Kim, J. A. M. Lopes

    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT   788   182 - 187  2015.07  [Refereed]

     View Summary

    The Active X-ray Spectrometer (AXS) is considered as one of the scientific payload candidates for a future Japanese mission, SELENE-2. The AXS consists of pyroelectric X-ray generators and a Silicon Drift Detector to conduct X-Ray Fluorescence spectroscopy (XRF) on the Moon to measure major elements: Mg, Al, Si, Ca, Ti, and Fe; minor elements: Na, K, F, S, Cr and Mn; and the trace element Ni depending on their concentration. Some factors such as roughness, grain size and porosity of sample, and the geometry of X-ray incidence, emission and energy will affect the XRF measurements precision. Basic studies on the XRF are required to develop the AXS. In this study, fused samples were used to make homogeneous samples free from the effect of grain size and porosity. Experimental and numerical studies on the XRF were conducted to evaluate the effects from incidence and emission angles and surface roughness. Angle geometry and surface roughness will be optimized for the design of the AXS on future missions from the results of the experiment and the numerical simulation. (C) 2015 Elsevier B.V. All rights reserved.

    DOI

  • Geochemical and Sm-Nd isotopic characteristics of the Late Archaean-Palaeoproterozoic Dhanjori and Chaibasa metasedimentary rocks, Singhbhum craton, E. India: Implications for provenance, and contemporary basin tectonics (vol 256, pg 62, 2015)

    S. De, R. Mazumder, T. Ohta, E. Hegner, K. Yamada, T. Bhattacharyya, J. Chiarenzelli, W. Altermann, M. Arima

    PRECAMBRIAN RESEARCH   262   121 - 122  2015.06  [Refereed]

    DOI

  • The evaluation of macroscopic and microscopic textures of sand grains using elliptic Fourier and principal component analysis: Implications for the discrimination of sedimentary environments

    Keita Suzuki, Hajime Fujiwara, Tohru Ohta

    SEDIMENTOLOGY   62 ( 4 ) 1184 - 1197  2015.06  [Refereed]

     View Summary

    A method that integrates elliptic Fourier and principal component analysis is a new development in the analysis of the shapes of sand grains. However, conventional elliptic Fourier and principal component analysis based on the variance-covariance matrix of the elliptic Fourier results can determine only the form of sand grains, and fails to quantify fine-scale boundary smoothness of grains. In this study, sand grains from glacial, fluvial, foreshore and aeolian environments were analysed using both elliptic Fourier and principal component analysis and an extension of elliptic Fourier and principal component analysis based on the correlation matrix to extract information on grain form (macroscopic) and grain boundary smoothness (microscopic) separately. Conventional elliptic Fourier and principal component analysis based on the variance-covariance matrix produces macroscopic particle shape descriptors, such as the elongation index and bump indices. These indices indicate that sand grains exposed to subaqueous transportation (fluvial and foreshore) have forms that are more elongated than those exposed to subaerial transportation (aeolian dunes). However, elliptic Fourier and principal component analysis based on the correlation matrix is, in addition, able to extract microscopic particle features, which can be interpreted in terms of a boundary smoothness index. The boundary smoothness index indicates that the surfaces of glacial grains are the most rugged, whereas the surfaces of aeolian grains are the smoothest. On bivariate plots of the boundary smoothness and elongation indices, samples from fluvial, foreshore, aeolian and glacial environments cluster in discrete regions. In addition, the analysis reveals that glacial grains are exposed to different morphological maturation pathways than those from fluvial, foreshore and aeolian environments.

    DOI

  • Geochemical and Sm-Nd isotopic characteristics of the Late Archaean-Palaeoproterozoic Dhanjori and Chaibasa metasedimentary rocks, Singhbhum craton, E. India: Implications for provenance, and contemporary basin tectonics

    S. De, R. Mazumder, T. Ohta, E. Hegner, K. Yamada, T. Bhattacharyya, J. Chiarenzelli, W. Altermann, M. Arima

    PRECAMBRIAN RESEARCH   256   62 - 78  2015.01  [Refereed]

     View Summary

    In significant contrast to other cratonic blocks of India, the Singhbhum cratonic successions record continuous depositional record from the Palaeoarchaean to Mesoproterozoic. Although the sedimentary facies characteristics and mode of stratigraphic sequence building of the Dhanjori and Chaibasa Formations are well known, sedimentary geochemistry, provenance and tectonic milieu of deposition of these two formations are hitherto unknown. The current manuscript presents geochemical and Sm-Nd isotopic data from the Dhanjori and Chaibasa Formations for the first time and combine previous sedimentological data with the goal to expand the framework for understanding the depositional and tectonic setting of these two formations. The Sm-Nd isotopic data for the Chaibasa clastics is unambiguous with respect to provenance. Average epsilon(Nd) (t = 2.2 Ga) = -0.8 +/- 1.0 and average Nd model age (TDM) = 2.51 +/- 0.08 Ga with average Sm-147/Nd-144 ratios = 0.1114 +/- 0.0041 for phyllites and quartzites indicate an extremely homogeneous source signature consistent with a late Archaean "juvenile" crustal provenance, possibly a dominantly upper crustal provenance. The Sm-Nd isotopic data from the older Dhanjori Formation also indicate broadly similar provenance as comparable lithologies in the younger Chaibasa Formation. Our Sm-Nd isotopic data is entirely consistent with the previous sedimentological data and confirms a terrestrial, riftdominated tectonic setting for the Dhanjori Formation (proximal sources, poorly mixed provenance) and a marginal marine to offshore setting for the more homogeneous Nd isotopic signature of the Chaibasa Formation (distal sources, well mixed provenance). (C) 2014 Elsevier B.V. All rights reserved.

    DOI

  • Palaeo-Mesoproterozoic sedimentation and tectonics of the Singhbhum Craton, eastern India, and implications for global and craton-specific geological events

    Rajat Mazumder, Shuvabrata De, Tohru Ohta, David Flannery, Leena Mallik, Trisrota Chaudhury, Priyanka Chatterjee, Marinah A. Ranaivoson, Makoto Arima

    Geological Society Memoir   43   139 - 149  2015

     View Summary

    The Singhbhum Craton in eastern India preserves a depositional record from the Palaeo-Mesoarchaean to the Mesoproterozoic. Herein, we have summarized the Palaeo-Mesoproterozoic supracrustal record of the Singhbhum Craton, discussed tectonosedimentary processes and discriminated Palaeo-Mesoproterozoic global and craton-specific events. The late Palaeo-Mesoproterozoic supracrustal record of the Singhbhum Craton is limited. It includes evidence for high continental freeboard conditions during 2.6- 2.1 Ga in the form of terrestrial deposits (alluvial fan-fluvial) of the Dhanjori Formation. This was followed by a major transgression and a transition to the relatively deeper-water shelf to shallow intertidal environments recorded by the Chaibasa Formation. A long hiatus ensued before deposition of the Dhalbhum Formation and conformably overlying Dalma and Chandil formations, suggesting continued high continental freeboard during 2.2-1.6 Ga. In significant contrast to the craton-specific Dhanjori Formation volcanism, the 1.7- 1.6 Ga plume-related Dalma volcanism was probably part of a global tectonothermal event.

    DOI

  • An active X-ray spectrometer for the SELENE-2 rover

    Kim K.J, Amano Y, Boyton W.V, Klingelhofer G, Brukner J, Hasebe N, Hamara D, Star R.D, Lim L.F, Ju G, Fagan T.J, Ohta T, Shibamura E

    Transactions of the Japan Society for Aeronautical and Space Sciences   12 ( 29 ) Pk35 - Pk42  2014.11

     View Summary

    The Active X-ray Spectrometer (AXS) for the Japanese SELENE-2 rover has been proposed for elemental analysis on the lunar surface to measure the major elements: Mg, Al, Si, Ca, Ti, and Fe; the minor elements, Na, K, P, S, Cl, Cr, and Mn and the trace element Ni, all depending on their concentrations at a landing site. The elemental data of the AXS allow us to not only classification but also quantification of surface rocks on the Moon. The AXS is a compact low-weight instrument for elemental analysis based on the principle of X-ray fluorescence spectrometry using an X-ray spectrometer and two (four) pyroelectric crystals as X-Ray Generators (XRG). This paper introduces the current status of the pre-project to develop an AXS for the SELENE-2 Rover including the investigations on the generation of X-ray flux of the XRG, required surface roughness for the XRS measurement, and a thermal design of the AXS.

  • P2-32 将来の惑星探査に向けた小型放射線分光装置の提案(ポスターセッション2,ポスター発表)

    長岡 央, 長谷部 信行, 草野 広樹, 内藤 雅之, 柴村 英道, 天野 嘉春, 太田 亨, フェイガン ティモシー, Waseda AXS team

    日本惑星科学会秋期講演会予稿集   2014   "P2 - 32"  2014.09

    CiNii

  • 低希釈ガラスビードによる岩石試料の蛍光X線分析:主成分元素と微量成分元素の同時測定法とその精度

    太田 亨

    学術研究(自然科学編)   62   1 - 9  2014.03

  • Paleoclimatic conditions and paleoweathering processes on Mesozoic continental redbeds from Western-Central Mediterranean Alpine Chains

    Francesco Perri, Tohru Ohta

    PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY   395   144 - 157  2014.02  [Refereed]

     View Summary

    Chemical and mineralogical analyses of the Triassic to lowermost Jurassic mudstones from continental redbeds outcropping in the Internal Domains of the Betic-Rifian and Calabria-Peloritani chains have been used to infer the relationships between paleoclimatic conditions and paleoweathering processes during rifting of a continental crust block that finally detached from adjoining western Tethyan realms to form an independent microplate (Mesomediterranean Microplate) from Jurassic to lower Miocene time. The studied mudstone samples come from Middle Triassic and Upper Triassic beds of the Saladilla Formation (both in the Betic Cordillera and in the Rif), whereas the Calabria-Peloritani Arc studied mudstones come from Upper Triassic to lowermost Jurassic beds (both in the Sila and Longi Taormina Units). Major and trace element concentrations, based on the massbalance calculation relative to the upper continental crust, show negative values both in Gibraltar and Calabria-Peloritani Arcs, implying that mudstone formation in the Early Mesozoic involved moderate to intense continental paleoweathering of the crust. In particular, CaO, Na2O, MgO, Sr, Ba, Fe2O3, MnO and transition metal elements (V, Cr, Co and Ni) are more depleted in the Triassic to Upper Jurassic samples of the Calabria-Peloritani samples than in the Middle to Upper Triassic Betic-Rifian samples, and suggest an increase of continental paleoweathering in the Mediterranean region from the Triassic to the Jurassic. In addition enrichment in SiO2, TiO2, Al2O3, 1(20 and incompatible elements in the Calabria-Peloritani Arc mudstones indicates sediment recycling effects that gradually increase from the Triassic to Jurassic time. The hinterland paleoweathering and sediment recycling effects have been mathematically distinguished using principal component analysis (PC1 is a measure of paleoweathering rate mainly due to humidity (positive values) against aridity (negative values), whereas PC2 corresponds to the extent of sediment recycling). The results strongly indicate that humidity had increased from the Triassic to the Jurassic and that the depositional environments in Calabria-Peloritani Arc were probably more suitable for sediment recycling. These seasonal climate alternations corresponding to an increase in paleoclimatic humidity that favored paleoweathering conditions and recycling processes. These results are also confirmed by the mineralogical data, which show a higher abundance of kaolinite, typical of warm-humid conditions, in the Calabria-Peloritani mudstones than in those of the Betic Cordillera and the Rif. Furthermore, the comparison among geochemical weathering index values of the studied samples and of recent soils from different climatic zones likely suggests a tropical rainforest climate in the studied area during the Triassic to the lowermost Jurassic. (c) 2013 Elsevier B.V. All rights reserved.

    DOI

  • An Active X-Ray Spectrometer for the SELENE-2 Rover

    Ja KIM Kyeong, AMANO Yoshiharu, V. BOYNTON William, KLINGELHÖFER Gostar, BRÜCKNER Johannes, HASEBE Nobuyuki, HAMARA Dave, D. STARR Richard, F. LIM Lucy, JU Gwanghyeok, J. FAGAN Timothy, OHTA Tohru, SHIBAMURA Eido

    TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, SPACE TECHNOLOGY JAPAN   12 ( 29 ) Pk_35 - Pk_42  2014

     View Summary

    The Active X-ray Spectrometer (AXS) for the Japanese SELENE-2 rover has been proposed for elemental analysis on the lunar surface to measure the major elements: Mg, Al, Si, Ca, Ti, and Fe; the minor elements, Na, K, P, S, Cl, Cr, and Mn and the trace element Ni, all depending on their concentrations at a landing site. The elemental data of the AXS allow us to not only classification but also quantification of surface rocks on the Moon. The AXS is a compact low-weight instrument for elemental analysis based on the principle of X-ray fluorescence spectrometry using an X-ray spectrometer and two (four) pyroelectric crystals as X-Ray Generators (XRG). This paper introduces the current status of the pre-project to develop an AXS for the SELENE-2 Rover including the investigations on the generation of X-ray flux of the XRG, required surface roughness for the XRS measurement, and a thermal design of the AXS.

    CiNii

  • Confirmation of a Middle Jurassic age for the Eedemt Formation in Dundgobi Province, southeast Mongolia: constraints from the discovery of new spinicaudatans (clam shrimps)

    Gang Li, Hisao Ando, Hitoshi Hasegawa, Masanobu Yamamoto, Takashi Hasegawa, Tohru Ohta, Noriko Hasebe, Niiden Ichinnorov

    ALCHERINGA   38 ( 3 ) 305 - 316  2014  [Refereed]

     View Summary

    Two spinicaudatan species, Triglypta eedemtensis Li sp. nov. and Dundgobiestheria mandalgobiensis Li gen. et sp. nov., are described on the basis of scanning electron microscopy (SEM) imaging of newly collected specimens from paper-thin laminated black shale of the Eedemt Formation exposed at the Eedemt locality in the Khootiin Khotgor coal mine region of Dundgobi Province in southeast Mongolia. Triglypta eedemtensis is ornamented mainly with puncta and a punctate fine reticulum; radial lirae occur only on two or three growth bands near the venter. The small spinicaudatan Triglypta is a common component of the Middle Jurassic Euestheria ziliujingensis fauna and Sinokontikia fauna, and is a typical taxon in the Middle Jurassic lacustrine sequences of northern Hebei and the Junggar and Turpan basins of the Xinjiang Autonomous District of China; however, it does not occur in stratigraphically higher units elsewhere. Therefore, the age of the Eedemt Formation should be considered Middle Jurassic rather than Early Cretaceous. The Eedemt Formation is much older than the Early Cretaceous Shinekhudag Formation in the Shine Khudag area of southeast Mongolia.

    DOI

  • フーリエ解析とフラクタル次元による砕屑物粒子の定量方法と堆積場判別方法の提示

    鈴木慶太, 酒井邦彦, 太田 亨

    地質学雑誌   119 ( 3 ) 205 - 216  2013.03

    DOI

  • 紀伊半島東部四万十帯北帯的矢コンプレックスの放散虫化石層序

    太田 亨, 大竹奈保, 森田信幸, 上村哲哉, 高橋奈美, 香味早央理, 坂 幸恭

    学術研究 自然科学編   61   9 - 29  2013.02

  • Quantitative evaluation of grain shapes by utilizing Fourier and fractal analysis and implications for discriminating sedimentary environments

    Suzuki Keita, Sakai Kunihiro, Ohta Tohru

    Jour. Geol. Soc. Japan   119 ( 3 ) 205 - 216  2013

     View Summary

    Fourier and fractal analysis methods have allowed new advancements in determining the shape of sand grains. However, the full quantification of grain shapes has not as yet been accomplished, partly due to the difficulties in interpreting the results of Fourier analysis, and partly because fractal dimension changes are somewhat dependent on the measuring techniques used. This study focuses on the application of a method that integrates elliptic Fourier and principal component analysis methods (elliptic Fourier-PCA). This method reduces the number of extracted variables and enables a visual inspection of the results of Fourier analysis, an approach that facilitates the understanding of the sedimentological significances of the results obtained using this technique. The application of this Elliptic Fourier-PCA technique to sand grains collected from fluvial, beach, and glacial environments produced particle descriptors such as elongation index (EF1) and multiple bump indices (EF2, EF3, and EF2 + EF3). These descriptors indicate that glacial, beach, and fluvial sediments contain particles with shapes similar to circles, ellipses, and cylinders, respectively. A modified pixel dilation (mPD) method was used for fractal dimension analysis, primarily as a simple model experiment proved that the mPD method enabled better detection of the degree of surface smoothness than traditional boxcounting methods. Mean (FD) and coefficient of variation of fractal dimension (FDCv) values decrease from glacial to fluvial and beach particles, indicating that glacial particles retain rugged surfaces, whereas beach particles have smoother and more even surfaces due to increased abrasion. Of the grain shape indices used during this study, the FD and EF1 variables are key shape proxies that enable differentiation between sedimentary environments, with an FD-EF1 plot allowing the effective discrimination of particles derived from fluvial, beach, and glacial environments.

    CiNii

  • 三重県志摩半島東部の黒瀬川帯中生界から見出されたジュラ紀・白亜紀放散虫化石

    太田 亨, 今井智文, 石田直人, 坂 幸恭

    地質学雑誌   118   588 - 593  2012.12

  • Jurassic-Cretaceous lacustrine deposits in the East Gobi Basin, southeast Mongolia

    Hisao Ando, Hitoshi Hasegawa, Takashi Hasegawa, Toru Ohta, Masanobu Yamamoto, Noriko Hasebe, Gang Li, Niiden Ichinnorov

    Journal of Geological Society of Japan   117 ( 11 ) XI - XII  2011.11

  • Identification of the Unchanging Reference Component of Compositional Data from the Properties of the Coefficient of Variation

    Tohru Ohta, Hiroyoshi Arai, Atsushi Noda

    MATHEMATICAL GEOSCIENCES   43 ( 4 ) 421 - 434  2011.05  [Refereed]

     View Summary

    In analyses of compositional data, it is important to select a suitable unchanging component as a reference to detect the behavior of a single variable in isolation. This paper introduces two tests for detecting the unchanging component, based on a new approach that utilizes the coefficient of variation of component ratios. That is, the coefficient of variation of a compositional ratio is subject to change when the unchanging component is switched between the denominator and numerator, and the coefficient of variation tends to be small when the unchanging component occurs as the denominator against any arbitrary components (Test 1). In addition, the ratio of the component pair that gives the lowest coefficient of variation is most likely to represent the two unchanging components (Test 2). However, Tests 1 and 2 are not necessary and sufficient conditions for uniquely finding the unchanging component. To verify the effectiveness of the tests, 500 artificial datasets were analyzed and the results suggest that the tests are able to identify the unchanging component, although Test 1 underperforms when the dataset includes a component with skewness greater than 0.5, and Test 2 fails when the dataset includes components with a correlation coefficient greater than 0.75. These defects can be overcome by interpreting the two test results in a complementary manner. The proposed tests provide powerful yet simple criteria for identifying the unchanging component in compositional data; however, the reliability of this approach needs to be assessed in further studies.

    DOI

  • Origin of rhythmical bedding in mid-Cretaceous lacustrine deposits, southeast Mongolia: Implication for terrestrial environmental changes during the OAE interval

    Hasegawa Hitoshi, Ando Hisao, Hasegawa Takashi, Ohta Toru, Yamamoto Masanobu, Hasebe Noriko, Li Gang, Ichinnorov Niiden

    Abstracts of Annual Meeting of the Geochemical Society of Japan   58 ( 0 ) 22 - 22  2011

    CiNii

  • Paleontological study on the Jurassic-lower Cretaceous Conchostracans from lacustrine deposits in the eastern Gobi basin, SW Mongolia

    Murata Takayuki, Li Gang, Ando Hisao, Hasegawa Hitoshi, Hasegawa Takashi, Ohta Toru, Yamamoto Masanobu, Hasebe Noriko, Ichinnorov Niiden

    Annual Meeting of the Geological Society of Japan   2011 ( 0 ) 504 - 504  2011

    CiNii

  • Clastic compositional variability induced by transport and sorting processes in bed load sediments of The Takase-River

    sakai kunihiro, ohta tohru

    Annual Meeting of the Geological Society of Japan   2011 ( 0 ) 465 - 465  2011

    CiNii

  • Testing the "weathering hypothese" for the Cretaceous OAEs in the Yezo Group, Teshionakagawa area, Hokkaido, Japan

    Kamigata Yuko, Ohta Tohru

    Annual Meeting of the Geological Society of Japan   2011 ( 0 ) 462 - 462  2011

    CiNii

  • Origin of immature sandstone in the Cretaceouse Yezo Group, Teshionakagawa area, Hokkaido

    Asano Sho, Ohta Tohru

    Annual Meeting of the Geological Society of Japan   2011 ( 0 ) 461 - 461  2011

    CiNii

  • Sedimentary facies and depositional environment of trench-fill deposits of the Shimanto Belt in the eastern Kii Peninsula

    Matsuda Yuto, Ohta Tohru

    Annual Meeting of the Geological Society of Japan   2011 ( 0 ) 442 - 442  2011

    CiNii

  • Early Cretaceous Terrestrial Weathering in Northern China: Relationship between Paleoclimate Change and the Phased Evolution of the Jehol Biota

    Tohru Ohta, Gang Li, Hiromichi Hirano, Takashi Sakai, Takeshi Kozai, Takenori Yoshikawa, Ai Kaneko

    JOURNAL OF GEOLOGY   119 ( 1 ) 81 - 96  2011.01  [Refereed]

     View Summary

    The Jehol Biota from lower Cretaceous deposits in northern China provides an important record of terrestrial fauna and flora, including feathered dinosaurs and one of the earliest angiosperms. This biota underwent three development phases, with a relatively limited biodiversity in the early phase that rapidly diversified in the middle phase. This study analyzes the conditions of terrestrial paleoweathering during the lower Cretaceous as inferred from the geochemistry of mudstones, with the aim of assessing the role of paleoclimate change as a background factor that led to the phased evolution of the Jehol Biota. The analysis focuses on the Dabeigou and Dadianzi formations of Hebei Province, northern China, which record the early and middle phases of the Jehol Biota, respectively. These fluviolacustrine sequences can be lithologically divided into lower and upper units. Geochemical weathering indices (e.g., W, Sigma REE [total amount of rare earth elements], and Delta W) show a significant increase from the lower to the upper unit, indicating enhanced weathering of the hinterland. Based on a comparison with the W values of recent soils that developed under various climates, the obtained increase in W can be interpreted as indicating temporal increases in temperature and humidity. Therefore, the increase in hinterland weathering from the lower to the upper unit was possibly induced by a shift in the paleoclimate to a more temperate and humid state. The timing of this change in paleoclimate closely coincides with a shift in the Jehol Biota to an evolved phase. Consequently, this preliminary result indicates that paleoclimate change in terrestrial regions of northern China might have contributed to the development of the Jehol Biota.

    DOI

  • The facies analysis and unconsolidated sediment deformation of the Cretaceous Matoya Complex in the Minamiise area, Mie Prefecture

    Matsuda Yuto, Nishiguchi Tatsuya, Ohta Tohru

    Annual Meeting of the Geological Society of Japan   2010 ( 0 ) 381 - 381  2010

    CiNii

  • Reconstruction of terrestrial paleoenvironmental changes during the intervals of Oceanic Anoxic Events (OAEs) from the Jurassic–Cretaceous lacustrine deposits in SE Mongolia

    Ando Hisao, Hasegawa Hitoshi, Hasegawa Takashi, Ohta Toru, Yamamoto Masanobu, Hasebe Noriko, Li Gang, Ichinnorov Niiden

    Annual Meeting of the Geological Society of Japan   2010 ( 0 ) 123 - 123  2010

    CiNii

  • Anew geochemical weathering index for evaluating crustal weathering and paleoclimate

    Ohta T, Kaneko A, Arai H

    Geochimica et Cosmochimica Acta   73 ( 13 ) A966 - A966  2009.05

  • 北海道北部天塩中川地域における空知層群ー蝦夷累層群境界の泥岩化学組成変動

    小林誠之, 太田 亨, 平野弘道

    三笠市立博物館紀要   13   21 - 34  2009.03

  • Measuring and adjusting the weathering and hydraulic sorting effects for rigorous provenance analysis of sedimentary rocks: a case study from the Jurassic Ashikita Group, SW Japan

    Ohta T

    Sedimentology   55   1687 - 1701  2008.11

    DOI

  • Statistical empirical index of chemical weathering in igneous rocks: A new tool for evaluating the degree of weathering

    Tohru Ohta, Hiroyoshi Arai

    CHEMICAL GEOLOGY   240 ( 3-4 ) 280 - 297  2007.06  [Refereed]

     View Summary

    Chemical weathering indices are useful tools in characterizing weathering profiles and determining the extent of weathering. However, the predictive performance of the conventional indices is critically dependent on the composition of the unweathered parent rock. To overcome this limitation, the present paper introduces an alternative statistical empirical index of chemical weathering that is extracted by the principal component analysis (PCA) of a large dataset derived from unweathered igneous rocks and their weathering profiles. The PCA analysis yields two principal components (PC1 and PC2), which capture 39.23% and 35.17% of total variability, respectively. The extent of weathering is reflected by variation along PC1, primarily due to the loss of Na2O and CaO during weathering. In contrast, PC2 is the direction along which the projections of unweathered felsic, intermediate and mafic igneous rocks appear to be best discriminated; therefore, PC1 and PC2 represent independent latent variables that correspond to the extent of weathering and the chemistry of the unweathered parent rock. Subsequently, PC1 and PC2 were then mapped onto a ternary diagram (MFW diagram). The M and F vertices characterize mafic and felsic rock source, respectively, while the W vertex identifies the degree of weathering of these sources, independent of the chemistry of the unweathered parent rock.
    The W index has a number of significant properties that are not found in conventional weathering indices. First, the W index is sensitive to chemical changes that occur during weathering because it is based on eight major oxides, whereas most conventional indices are defined by between two and four oxides. Second, the W index provides robust results even for highly weathered sesquioxide-rich samples. Third, the W index is applicable to a wide range of felsic, intermediate and mafic igneous rock types. Finally, the MFW diagram is expected to facilitate provenance analysis of sedimentary rocks by identifying their weathering trends and thereby enabling a backward estimate of the composition of the unweathered source rock. (C) 2007 Elsevier B.V. All rights reserved.

    DOI

  • 組成データ解析における0値および欠損値の扱いについて

    新井宏嘉, 太田 亨

    地質学雑誌   112 ( 7 ) 439 - 451  2006.07

  • 対数比法における規格化成分選定プログラム—Woronow-Love-Schedl法の自動化—

    新井宏嘉, 太田 亨

    地質学雑誌   112 ( 6 ) 430 - 435  2006.06

  • 組成データ解析の問題点とその解決方法

    太田 亨, 新井宏嘉

    地質学雑誌   112 ( 3 ) 173 - 187  2006.03

  • 西九州黒瀬川帯における中生代堆積盆の埋積作用と堆積環境変遷史

    太田 亨

    平成16年度深田研究助成研究報告     17 - 30  2005.12

  • Geochemistry of Jurassic to earliest Cretaceous deposits in the Nagato Basin, SW Japan: implication of factor analysis to sorting effects and provenance signatures

    T Ohta

    SEDIMENTARY GEOLOGY   171 ( 1-4 ) 159 - 180  2004.10  [Refereed]

     View Summary

    One of the intractable problems in provenance analysis is the hydraulic sorting effect and resultant mineralogical heterogeneity in coarse- and fine-grained sediments which conceals provenance characteristics. The present study uses factor analysis to address geochemical responses to the sorting effect and provenance of Late Mesozoic sediments in the Nagato Basin, SW Japan. Factor analysis has proven useful for comprehending geochemical gradients between coarse- and fine-grained sediments. In the present example, compositional differences are based on varying proportions of quartz, plagioclase, chrome spinel, authigenic minerals and phyllosilicates. The contrasting behaviors of these minerals during the depositional stage resulted in the systematic fractionation Of SiO2/Al2O3, Na2O/K2O and Cr/Ba. Sandstones and mudstones exhibit an array of compositions in SiO2/Al2O3-Na2O/K2O and SiO2/Al2O3--Cr/Ba diagrams, the ranges of which reflect compositional variations due to the sorting effect. Sediments of different provenance exhibit distinctive mineral arrays and can be discriminated simply by reading the gradients of the continua. Therefore, this kind of data management concurrently quantifies the sorting effect and allows an estimation of the original source material. The SiO2/Al2O3-Na2O/ K2O diagram is particularly useful for scrutinizing igneous and mature continental provenances, while the SiO2/Al2O3-Cr/ Ba diagram ascertains contributions from mafic sources. This investigative approach delineates a systematic provenance transition within the Nagato Basin: a serpentinite melange provenance in the early Early Jurassic, a magmatic arc in the late Early to middle Middle Jurassic and a continental interior in the latest Jurassic to earliest Cretaceous. The provenance changed by the direct input of mature continental material into the Nagato Basin, which resulted from dissection of the volcanic arc. (C) 2004 Elsevier B.V All rights reserved.

    DOI

  • First occurence of Haugia cf. variabilis (d'Orbigny) (Ammonoidea) from the Lower Jurassic of the Uminoura area, western Kyushu, Japan

    Ryoji Wani, Tohru Ohta, Hiromichi Hirano

    Paleontological Research   8 ( 2 ) 123 - 128  2004.06

     View Summary

    Haugia cf. variabilis (d'Orbigny) has been found in the upper part of the Idenohana Formation in the Uminoura area, Kumamoto Prefecture. This species is originally known from the Upper Toarcian H. variabilis Subzone of the Lytoceras jurense Zone in western Europe. This occurrence combined with our analyses of the lithofacies and sequence stratigraphy suggests that the Idenohana Formation is conformably overlain by the Kyodomari Formation. © by the Palaeontological Society of Japan.

    DOI

  • Deep-marine sedimentation and sequence-evolution of the Toyora Group in the Nagato Basin, Inner Zone of SW Japan

    Tohru Ohta, Takashi Sakai

    Journal of the Geological Society of Thailand, Special Issue   ( 1 ) 45 - 60  2004.05

  • 西九州海浦地域の黒瀬川構造帯中・古生界層序の改訂とジュラ系葦北層群(新称)の層序

    太田 亨, 坂井 卓

    地質学雑誌   109 ( 12 ) 671 - 688  2003.12

  • Upper Jurassic-Cretaceous deposits of East Asian continental margin along the Amur River

    Kirillova, G.L, Natal'in, S.V, Zyabrev, T, Sakai, T, Ishida, K, Ishida, N, Ohta, T, Kozai, T

    Field excursion guidbook, The 4th International Symposium of IGCP434    2002.08

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Books and Other Publications

  • 地球・環境・資源 : 地球と人類の共生をめざして

    高木, 秀雄, 山崎, 淳司, 円城寺, 守, 小笠原, 義秀, 太田, 亨, 守屋, 和佳, 内田, 悦生, 大河内, 博, 香村, 一夫( Part: Joint author)

    共立出版  2019.03 ISBN: 9784320047341

  • 日本の地質構造百選

    日本地質学会構造地質部会編

    朝倉書店  2012.05 ISBN: 9784254162738

Research Projects

  • Verification of abrupt climate change in hothouse climate state from lacustrine varve record

    Project Year :

    2019.04
    -
    2022.03
     

  • 東アジア大陸における白亜紀古気候の時空変化:温暖期の大気循環システムの解明

    Project Year :

    2018.04
    -
    2021.03
     

     View Summary

    2018年度の研究では、北緯25°付近(北ベトナム)において、白亜紀中~後期に熱帯雨林気候から、極度の砂漠気候に移行したことを確かめた。これを受けて、2019年度は調査範囲を広げて、中国浙江省と中南部ベトナムを調査対象に追加した。このことによって、北緯20°~30°における広範囲の古気候を明らかにすることを目指した。浙江省において白亜紀当時の後背地風化度を解析した結果、温室モードの前期白亜紀では温暖湿潤気候(風化指標W値の値=60前後)から、極温室モードの中期白亜紀で乾燥気候(W値=40前後)に古気候が移行したという結果を得た。同様に、中南部ベトナムにおいては、温室モードの前期白亜紀では熱帯雨林気候(W=90前後)、極温室モードの中期白亜紀では温暖湿潤気候(W=60前後)という古気候変遷を示す結果を得た。新規解析した浙江省も中南部ベトナム両地域において、地球温暖化の時期に乾燥化が進行したことを確認したが、乾燥化の規模は北ベトナムにおけるそれより過酷なものではなかった。この事実は、熱帯雨林地域の砂漠化の範囲が、北緯25°(北ベトナム)が中心で、その北限が北緯30°(浙江省)付近、南限が北緯20°(中南部ベトナム)付近であったことを示しており、中期白亜紀に突如として始まった砂漠化の地理的範囲を特定することにつながった。浙江省・北ベトナム・中南部ベトナムにおいて採取した試料については、化学組成の分析は完了している。化学組成から、後背地・続成作用・後背地風化度の解析を進めている。後背地風化度については、前述したように、中期白亜紀にアジア大陸低緯度地域が砂漠化したことを示すことができた。かつ、その砂漠化の範囲の広がりを推定するデータを得ることができた。この結果を追認するために、粘土鉱物組成という別角度からも後背地風化度の定量を現在進行形で実施中である。北ベトナムについてはデータを出しており、砂漠化を検知した中期白亜紀には熱帯雨林気候の土壌にみられるカオリナイトが欠如していることを確認した。このように、マルチプロキシから上記の気候変遷の追認を進めている。上記のように、中期白亜紀の極温暖化によって低緯度地域が砂漠化したことが明らかになった。今後は低緯度砂漠化の影響範囲をより明確にするのと共に、赤道直下では古環境を明らかにしていきたい。そのために、南ベトナムPhu Quoc島の白亜系と、ボルネオ島Sawarakに分布する白亜系の現地調査と機器分析を実施する予定であった。白亜紀当時のPhu Quoc島の古緯度は北緯15°程度であり、Sawarakのそれは0°である。したがって、この調査地域選定によって、極温暖期における熱帯収束帯の気候応答を明らかにできると期待される。しかし、新型コロナウイルスの影響でベトナムとマレーシアへの海外渡航が困難になった問題が発生した。幸いなことに、本年度9月からベトナムから本研究課題によって学位取得を目指している博士課程留学生を迎える予定である。当該学生は現在ベトナムに滞在しており、ベトナム国内であれば新型コロナウイルスによる行動制限が課されていない。そこで、当該学生にPhu Quoc島の現地調査と試料のサンプリングを行ってもらい、秋以降に本研究室において試料の危機分析を実施することを計画している。本年度は同時に、中南部ベトナムと浙江省の試料について、X線回折装置による分析を実施し、粘土鉱物組成から後背地風化度を評価する計画である。解析結果は、北ベトナムのそれと比較しながら、中期白亜紀の極温暖モードにおける砂漠気候帯の広がりを認定する

  • Sand grain shape analysis by Elliptic Fourier-Principal Component Analysis: proposal of an index to determine paleo-wave energy

    Project Year :

    2015.04
    -
    2018.03
     

     View Summary

    This study investigated the relationship of foreshore grain shapes and wave/wind power. Principal component analysis revealed that PC1 represents wave power and it showed a positive correlation with roundness index, and foreshores facing Pacific and Sea of Japan showed contrasting values. Therefore, this latent value indicates that grains tend to be rounded in large oceans that are frequently attacked by swells. PC2 represents wind power and showed positive correlation with smoothness index, and showed high values where aeolian dunes are developed. Therefore, this latent value illustrates the degree of development of strand plain and, that in such environment, grain surfaces tend to be smooth. Application of the present result enables to predict the size of the ocean and presence of aeolian dunes simply from the analysis of grain shapes

  • Core-drilling survey of Cretaceous lacustrine deposits in Mongolia: land-ocean linkage during OAE period on tens of thousands year scale

    Project Year :

    2013.04
    -
    2016.03
     

     View Summary

    Detailed cyclic stratigraphy of the lacustrine Lower Cretaceous Shinekhudag Formation distributed in Gobi desert, southeast Mongolia, is established through outcrop and three drilled core sections. In terms of radiometric age measurements by FT and U/Pb methods for zircon grains from intercalated tuffaceous layers, the depositional age of the Shinekhudag Formation can be estimated to be during 123-119 Ma (early Aptian).Several kinds of analyses for annual varve thickness and chemical proxy in mudstone sequences, show climatic and lake-level changes controlled, respectively by solar forcing (11, 88 and 400 yrs) and orbital cycles (20, 100 and 400 kyrs). Therefore, the Shinekhudag lacustrine deposits are interpreted to record the millennial- to orbital-scale paleoclimatic changes in mid-latitude Asia during the Aptian period

  • Quantatitative evaluation of chemical weathering effect and development of paleoclimate index

    Project Year :

    2010.04
    -
    2013.03
     

     View Summary

    The present study aims to unravel the relationship between geochemical changes during soil formation and relevant climatic conditions that induce geochemical modification. As a result, newly invented geochemical index successfully discriminated soils developed on boreal, boreal humid, steppe, temperate humid, arid, semi-arid and tropical rainforest climates. This eochemical index could be applied to paleosols to evaluate climatic condisions of the past. Applications to the Cretaceous strat in Hokkaido and Northern China revaled that geochemical paleoweathering W index are concordant with paleoclimatic changes, and verified that the W index would serve as a new paleoclimate proxy

  • Evolutionary paleontologic, stratigraphic, and geochemical studies on the Cretaceous environmental changes.

     View Summary

    (1)We studied the stratigraphic transition of major and minor elements in terms of some statistical methods from the Sorachi to the Yezo Group as well as of radiolarian abundance and specific compositions. in Teshionakagawa area, Hokkaido. We clarified that the chemical transition is much different from the clear visual change in the succession between the upper Sorachi and the lower Yezo Groups.(2)We made a joint work on the same sections of the upper Cretaceous in Nakatonbetsu area, Hokkaido from the viewpoints of biostratigraphy by using ammonoids, inoceramids, planktonic foraminifers, sequence stratigraphy, and stable carbon isotope stratigraphy. We detected a significant spike of carbon isotope fluctuation at the same stratigraphic horizon of the extinction of inoceramid bivalves. This result enable us to make a high resolution international correlation.(3)We made a joint research on the Jixi Group in NE China of the provenance of the Yezo forearcc basin from the viewpoints of biostratigraphy of marine bivalves, pollen, stable carbon isotope stratigraphy and sequence stratigraphy. We obtained a high resolution correlation of the group with the Japanese Pacific, and European sections

  • Correlation and paleoenvironmental analyses on the Yezo Group and Jehol Group equivalents by means of bio-, stable carbon isotope-, and sequence-stratigraphy.

     View Summary

    (1) We obtained many additional samples from the Chengzihe Formation of the Jixi Group of Heilongjiang Province, increased many analytical results, and improved stratigraphic resolution for the international correlation. (2) We obtained analytical samples from the drilling core of the Jixi Group in Bolli City and made a stable carbon isotope analysis. The result leads us to correlate the core with the lower Chengzihe Formation of the group. (3) We made stratigraphic research on the Dabeigou, Dadianzi, Siegayan, and Nantian Formations in Hebei Province. (4) We made sedimentological research on the Lower Cretaceous System in Yanji City, Jilin Province. We obtained the atmospheric pCO2 from the calcareous nodules of the lower Cretaceous. (5) We expanded our analytical methods to the Lower Jurassic in Chonqin City

  • Terristrial humidity increase during mid-Cretaceous : Cretaceous research in Mongolia for understanding of greenhouse Earth system

     View Summary

    The lacustrine deposits of the mid-Cretaceous Shinekhudag Formation and middle Jurassic Eedemt Formation in southeast Mongolia are investigated through the following two strategy : (1) Establishment of chronostratigraphy by carbon-isotopic stratigraphy, conchostracans biostratigraphy, and fission-track age dating of intercalated tuffaceous rocks, and (2) Reconstruction of terrestrial paleoclimatic changes by cyclicity of the rhythmically alternating shale-dolomite, paleoweathering changes based on mineral and major elemental ratios, and paleotemperature changes based on organic geochemical proxy (TEX_<86>). The results reveal that these lacustrine strata record orbital-controlled paleoclimatic (precipitation and temperature) changes in inland Asia during the OAE intervals

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Presentations

  • 北海道蝦夷層群における白亜紀海洋無酸素事変の原因としての“風化仮説”の検証

    上形由布子, 高木悠花, 太田亨

    日本地質学会第122年学術大会 

    Presentation date: 2015.09

  • 四万十帯砕屑物組成の時間・空間変化様式:琉球と三重地域の広域比較

    広瀬健, 葛原弘毅, 太田亨

    日本地質学会第122年学術大会 

    Presentation date: 2015.09

  • 楕円フーリエ−主成分分析法を用いた砕屑物粒子形状の定量化および堆積場判別手法の検証

    橋本朋子, 太田亨

    日本地質学会第122年学術大会 

    Presentation date: 2015.09

  • インド東北部スインブーム地塊に分布する前期原生代潮汐堆積物のウェーブレット解析:20億年前の地球自転速度の推定

    宮田浩之, 太田亨

    日本地質学会第122年学術大会 

    Presentation date: 2015.09

  • 月着陸探査に向けた能動型蛍光X線分光計の開発状況

    日本地球惑星科学連合 

    Presentation date: 2015.05

  • 次期月惑星着陸探査計画に向けた蛍光X線分析法の検討 —試料の表面粗さと特性X線強度比の関係—

    日本地球惑星科学連合 

    Presentation date: 2015.05

  • 深海堆積物の地球化学組成による堆積水深・堆積速度・運搬距離の推定方法:イタリア、イオニア海を例として

    日本堆積学会2015年つくば大会 

    Presentation date: 2015.04

  • 石英粒子のカソード・ルミネッセンス特性による 源岩の判別方法の提示

    地質学会第121年学術大会 

    Presentation date: 2014.09

  • 多変量統計学による花崗岩由来の腐食岩・土壌の物性値と化学組成の関係解析

    地質学会第121年学術大会 

    Presentation date: 2014.09

  • 新疆−ウイグル自治区に分布する白亜系湖成層の可視分光・化学分析による古環境解析

    地質学会第121年学術大会 

    Presentation date: 2014.09

  • タイ北東部に分布するコラート層群の全岩化学組成を用いた後背地および古環境解析

    地質学会第121年学術大会 

    Presentation date: 2014.09

  • 沖縄県における秩父帯および四万十帯砕屑物の全岩化学組成と砂岩モード組成を用いた後背地解析

    地質学会第121年学術大会 

    Presentation date: 2014.09

  • 中期白亜紀における海洋無酸素事変の新作業仮説“風化仮説”の室内実験検証

    地質学会第121年学術大会 

    Presentation date: 2014.09

  • Provenance and paleoclimate during Cretaceous in northeastern Thailand: Mineralogy and geochemistry of the Khorat Group

    IGCP608 Second International Conference 

    Presentation date: 2014.09

  • Base level and paleotemperature changes of Cretaceous lacustrine succession in southeast Mongolia

    IGCP608 Second International Conference 

    Presentation date: 2014.09

  • Paleoenviromental of Cretaceous lacustrine succession in Xinjiang-Uygur Autonomous Region: Development of mega-monsoon climate regime as a cause of high-frequent reversals of redox conditions in the lacustrine environment

    IGCP608 Second International Conference 

    Presentation date: 2014.09

  • Laboratory experiments for attesting the “weathering hypothesis” as a possible cause of the mid-Cretaceous Oceanic Anoxic Events

    IGCP608 Second International Conference 

    Presentation date: 2014.09

  • Evidence of enhanced continental weathering during oceanic anoxic event 2 (OAE 2) in eastern continental margin of Asia

    IGCP608 Second International Conference 

    Presentation date: 2014.09

  • Provenance analysis of clastic sediments of the Chichibuand Shimanto Belts in Okinawa Prefecture using modal and whole-rock chemical compositions

    IGCP608 Second International Conference 

    Presentation date: 2014.09

  • Reconstruction of terrestrial paleo-hydrological change during the mid-Cretaceous “Supergreenhouse” period: Insights from the lacustrine records (Shinekhudag Fm.) of southeast Mongolia

    IGCP608 Second International Conference 

    Presentation date: 2014.09

  • Stratigraphic succession of Conchostracan fossils from the lacustrine deposits in the Shinekhudag area (Lower Cretaceous), Eastern Gobi basin, Southeast Mongolia

    IGCP608 Second International Conference 

    Presentation date: 2014.09

  • TEX86-based lake water temperatures in Jurassic and Cretaceous Mongolia

    IGCP608 Second International Conference 

    Presentation date: 2014.09

  • Evidence of enhanced continental weathering during oceanic anoxic event 2 (OAE 2) in the western Panthalassa (proto-Pacific) Ocean

    International Sedimentological Congress 2014 

    Presentation date: 2014.08

  • The evaluation of sand grain shape using elliptic Fourier and principal component analysis: implications for the discrimination of sedimentary environments

    International Sedimentological Congress 2014 

    Presentation date: 2014.08

  • Increased Luminosity of Pyroelectric X-ray Generator for Active X-ray Spectrometer on SELENE-2

    AOGS 11th Annual Meeting 

    Presentation date: 2014.07

  • モンゴルの年縞湖成層のラミナレベル解析: 白亜紀中期“超温室期”の年スケール気候システム変動の解明に向けて

    日本堆積学会 

    Presentation date: 2014.03

  • Taphonomy and paleoecology of the Lower Cretaceous conchostracans from lacustrine deposits in the eastern Gobi Basin, southeast Mongolia

    IGCP608 first international symposium 

    Presentation date: 2013.12

  • Climatic change of the Junggar basin accompanied by the elevation of the Tianshan Mountains during the Early Cretaceous

    IGCP608 first international symposium 

    Presentation date: 2013.12

  • Terrestrial paleoenvironments during the intervals of Oceanic Anoxic Events reconstructed from the Cretaceous lacustrine deposits in southeast Mongilia

    IGCP608 first international symposium 

    Presentation date: 2013.12

  • First report on Cretaceous paleoweathering rates in western Panthalassa: Evidence of global enhancement of continental weathering during OAE 2

    IGCP608 first international symposium 

    Presentation date: 2013.12

  • Quantitative evaluation of grain shapes by utilizing elliptic Fourier and principal component analyses: Implications for sedimentary environment discrimination

    AGU 

    Presentation date: 2013.12

  • First report on Cretaceous paleoweathering rates in western Panthalassa: Evidence of global enhancement of continental weathering during OAE 2

    AGU 

    Presentation date: 2013.12

  • 楕円フーリエ解析を用いた砕屑物粒形の定量法と堆積場判別方法の提示

    地質学会第120年学術大会 

    Presentation date: 2013.09

  • 東アジア大陸における白亜紀大陸地殻風化度:海洋無酸素事変と風化度増大の関係性

    地質学会第120年学術大会 

    Presentation date: 2013.09

  • モンゴル南東部白亜系湖成層における鉱物・全岩化学組成を用いた湖水面および古気温変動の解読

    地質学会第120年学術大会 

    Presentation date: 2013.09

  • 石英粒子のカソード・ルミネッセンス特性による源岩の判別方法の提示

    地質学会第120年学術大会 

    Presentation date: 2013.09

  • 東アジア大陸における下部白亜系の後背地風化過程と古気候帯の復元

    地質学会第120年学術大会 

    Presentation date: 2013.09

  • 変動係数による組成データ内の不変成分の特定とその検証

    地質学会第120年学術大会 

    Presentation date: 2013.09

  • Lunar Surface Investigation using an Active X-ray Spectrometer for the SELENE-2 Rover

    AOGS 2013 

    Presentation date: 2013.06

  • Lunar Surface Investigation using an Active X-ray Spectrometer for the SELENE-2 Rover

    AOGS2013 

    Presentation date: 2013.06

  • Development of X-ray Generator for Active X-ray Spectrometer on SELENE-2/Rover

    AOGS2013 

    Presentation date: 2013.06

  • SELENE-2用月面探査車搭載に向けた化学分析装置AXSの開発

    宇宙科学シンポジウム 

    Presentation date: 2013.01

  • AN ACTIVE X-RAY SPECTROMETER PROPOSED FOR THE SELENE-2 ROVER

    IPM2012 

    Presentation date: 2012.10

  • Jurassic to Early Cretaceous T-R cycles in East Asian continental margin and tis tectonic implication

    International Association of Sedimentologists 

    Presentation date: 2012.09

  • New rigorous provenance discrimination diagrams restoring original source rock compositions by adjusting the effects of source area weathering and hydraulic sorting processes

    International association of Sedimentologists 

    Presentation date: 2012.09

  • Effects of fluvial and coastal sorting processes to the composition of sediments: Implications for protolith reconstruction and discrimination of depositional environment

    international Association of Sedimentologists 

    Presentation date: 2012.09

  • Examination of weathering hypothesis as a cause of the Cretaceous OAEs: A case study from the Yezo Group, northern Japan

    International Association of Sedimentologists 

    Presentation date: 2012.09

  • セレーネ2搭載用能動型 X 線分光計

    第45回月・惑星シンポジウム 

    Presentation date: 2012.08

  • AN ACTIVE X-RAY SPECTROMETER PROPOSED FOR THE SELENE-2 ROVER

    39th COSPAR Scientific Assembly 

    Presentation date: 2012.07

  • AN ACTIVE X-RAY SPECTROMETER (AXS) FOR THE ROVER OF THE JAPANESE SELENE-2 MISSION FOR CHEMICAL IN-SITU CHARACTERIZATION OF LUNAR MATERIAL

    European Lunar Symposium 

    Presentation date: 2012.07

  • Conchostracan fossils and rhythmic occurrence of the lacustrine deposits in the Shinekhudag area (Lower Cretaceous), Eastern Gobi basin, southeast Mongolia

    Presentation date: 2012.06

  • Compositional variability in fluvial bed load sediments induced by transport and sorting processes: implications for protolith reconstruction

    Presentation date: 2012.06

  • The Evolutional history of the Archean to Paleoproterozic Singhbhum basin in northeast India

    Presentation date: 2012.06

  • Orbital-controlled lake-level and productivity changes in the Aptian lacustrine deposits in SE Mongolia: Implications for paleo-hydrologic changes during the OAE1a&#8211;1b interval

    Presentation date: 2012.06

  • Orbital-controlled lake-level and productivity changes in the Aptian lacustrine deposits in SE Mongolia: Implications for paleo-hydrologic changes during the OAE1a–1b interval

    Presentation date: 2012.06

  • Base level changes of Cretaceous lacustrine succession in southeast Mongolia determined by mineral and chemical compositions of mudstones.

    Presentation date: 2012.06

  • Paleoclimate analysis of the Lower Cretaceous deposits in North China and relationship with evolution of the Jehol Biota

    Presentation date: 2012.06

  • Quantitative evaluation of grain shapes by utilizing Fourier and fractal analyses and implications for discriminating sedimentary environments

    Presentation date: 2012.06

  • Relationship between Early Cretaceous terrestrial weathering process and paleogeography, paleoclimate in northern China, Liaoning and Heilongjiang Provinces

    Presentation date: 2012.06

  • Lithostratigraphy, geochemistry and mineralogy of drilled core in off New Zealand, IODP Expedition 329: Cretaceous to Tertiary paleo-environmental changes in the South Pacific

    Presentation date: 2012.06

  • Orbital-scale lake-level and productivity changes in the mid-Cretaceous lacustrine deposits in southeast Mongolia

    Presentation date: 2012.05

  • AN ACTIVE X-RAY SPECTROMETER (AXS) FOR THE ROVER OF THE JAPANESE SELENE-2 MISSION FOR CHEMICAL IN-SITU CHARACTERIZATION OF LUNAR MATERIAL

    European Lunar Symposium 

    Presentation date: 2012.04

  • INTRODUCTION TO THE SCIENTIFIC INVESTIGATIONS OF AN ACTIVE X-RAY SPECTROMETER FOR THE SELENE-2 ROVER

    43rd Lunar and Planetary Science Conference (2012) 

    Presentation date: 2012.03

  • SELENE-2搭載に向けた能動型蛍光X線分光計AXS

    応用物理学会 

    Presentation date: 2012.03

  • Introduction to the scientific investigations of Active X-ray Spectrometer for the SELENE-2 rover

    The 6th KAGUYA (SELENE) Science Working Team Meeting 

    Presentation date: 2012.01

  • 月面でのその場元素分析のための能動型蛍光X線分光計AXSの開発状況

    第12回宇宙科学シンポジウム 

    Presentation date: 2012.01

  • モンゴルの白亜系湖成層中に見られる堆積リズムの起源:白亜紀海洋無酸素事変期の陸域環境変動解明に向けて

    日本堆積学会 

    Presentation date: 2011.12

  • モンゴル南東部のジュラ系−白亜系湖成頁岩層から復元する海洋無酸素事変期の陸域古環境

    日本堆積学会 

    Presentation date: 2011.12

  • SELENE-2搭載に向けたその場元素分析のための能動型蛍光X線分光計AXSの開発

    太陽系科学シンポジウム 

    Presentation date: 2011.11

  • モンゴル南東部,ゴビ砂漠における湖成堆積物中のジュラ系ー下部白亜系カイエビの古生物学的研究

    日本地質学会第118年学術大会 

    Presentation date: 2011.09

  • アポロ試料の主要元素組成に基づく宇宙風化度の定量

    日本鉱物科学会2011年学術大会 

    Presentation date: 2011.09

  • 九州黒瀬川帯西部日奈久地域の下部白亜系層序と堆積相解析

    日本地質学会第118年学術大会 

    Presentation date: 2011.09

  • 北海道天塩中川地域に分布する白亜系蝦夷層群の未成熟砂岩の起源

    日本地質学会第118年学術大会 

    Presentation date: 2011.09

  • 北海道天塩中川地域の蝦夷層群における白亜紀OAE”風化仮説”の検証

    日本地質学会第118年学術大会 

    Presentation date: 2011.09

  • 運搬・淘汰作用による福島県,高瀬川河床堆積物の組成改変過程

    日本地質学会第118年学術大会 

    Presentation date: 2011.09

  • 紀伊半島東部の四万十帯に分布する海溝充填堆積物の堆積相と堆積環境

    日本地質学会第118年学術大会 

    Presentation date: 2011.09

  • Early Cretaceous terrestiral weathering in NE China: Relationship between paleocliamte change and the phased evolution of the Jehol Biota

    6th Symposium of the IGCP 507 

    Presentation date: 2011.08

  • Origin of rhythmical beddings in the Aptian lacustrine deposits (Shinekhudag Formation) in Southeast Mongolia

    6th Symposium of the IGCP 507 

    Presentation date: 2011.08

  • Conchostracans from lacustrine deposits in the Eastern Gobi Basin, southeastern Mongolia

    6th Symposium of the IGCP 507 

    Presentation date: 2011.08

  • Origin of widespread sedimentary basins along the eastern margin of Asian continent during the Early Cretaceous

    6th Symposium of the IGCP 507 

    Presentation date: 2011.08

  • Paleoenvironmenttal and paleoclimatic reconstruction of the Jurassic-Lower Cretaceous lacustrine deposits in the eastern Gobi Basin, southeast Mongolia

    6th Symposium of the IGCP 507 

    Presentation date: 2011.08

  • Toward the international correlation of the Jehol Group-technical problems of stable carbon isotope stratigraphy

    6th Symposium of the IGCP 507 

    Presentation date: 2011.08

  • Tests for identifying the unchanging reference component of compositional data using the properties of the coefficient of variation

    CoDaWork'11 

    Presentation date: 2011.05

  • モンゴル南東部のジュラ系ー白亜系湖成頁岩層から復元する海洋無酸素事変期の陸域古環境(概報)

    日本古生物学会第160回例会 

    Presentation date: 2011.01

  • Reconstruction of terrestrial paleoenvironmental changes during the intervals of Oceanic Anoxic Events (OAEs) from the Jurassic&#8211;Cretaceous lacustrine deposits in Southeast Mongolia

    5th International symposium of the IGCP507 

    Presentation date: 2010.10

  • Reconstruction of terrestrial paleoenvironmental changes during the intervals of Oceanic Anoxic Events (OAEs) from the Jurassic–Cretaceous lacustrine deposits in Southeast Mongolia

    5th International symposium of the IGCP507 

    Presentation date: 2010.10

  • 三重県南伊勢市に分布する白亜系的矢コンプレックスの堆積相解析および未固結時変形構造

    日本地質学会第117年学術大会 

    Presentation date: 2010.09

  • Reconstruction of terrestrial paleoenvironmental changes during the intervals of Oceanic Anoxic Events (OAEs) from Jurassic-Cretaceous lacustrine deposits in SE Mongolia

    Presentation date: 2010.09

  • モンゴルのジュラ系&#8211;白亜系湖成層を対象とした陸域古環境変遷の高解像度復元

    日本地球惑星科学連合2010年大会 

    Presentation date: 2010.05

  • モンゴルのジュラ系–白亜系湖成層を対象とした陸域古環境変遷の高解像度復元

    日本地球惑星科学連合2010年大会 

    Presentation date: 2010.05

  • Paleoenvironmental and paleoclimatic reconstruction of the Lower Cretaceous lacustrine deposit (Shinekhudag Fm) in the eastern Gobi Basin, southeastern Mongolia: Perspective and preliminary results

    4rd International Symposium of the IGCP 507 

    Presentation date: 2009.12

  • Paleoclimate conditions during the evolution of the Jehol Biota: A case study from Lower Cretaceous lacustrine deposits in Luanping, Hebei Province, NE China

    4rd International Symposium of the IGCP 507 

    Presentation date: 2009.12

  • 中国東北部・河北省の下部白亜系河川ー湖沼堆積物の後背地風化過程と古気候解析

    日本地質学会第116年学術大会 

    Presentation date: 2009.09

  • 中国東北部の白亜紀前期熱河層群の堆積盆テクトニクス

    日本地質学会第116年学術大会 

    Presentation date: 2009.09

  • Toward the more precise correlation of non-marine beds. An example of the stable carbon isotope stratigraphy of the Jixi Group, Heilongjiang

    Presentation date: 2009.08

  • A new geochemical index for evaluating crustal weathering and paleoclimate

    Goldscmidt 2009 

    Presentation date: 2009.06

  • Fresh-water bivalve shell beds from the lower Cretaceous Dabeigou Formation in northeast China

    Presentation date: 2009.06

  • 風化作用と淘汰作用による砕屑物組成の改変過程と源岩組成の復元方法

    日本地質学会第115年学術大会 

    Presentation date: 2008.09

  • 東アジア東縁部の前期白亜紀堆積盆の堆積サイクル

    日本地質学会第115年学術大会 

    Presentation date: 2008.09

  • Mid-Cretaceous basin tectonis in Tan-Lu fault system, continental margin of east Asia: An approach from sequence stratigraphy

    3rd International Symposium of the IGCP 507 

    Presentation date: 2008.08

  • Paleowethering and paleoclimate conditions of the Lower Cretaceous fluvio-lacustrine deposits in Luanping, Hebei Province, NE China

    3rd International Symposium of the IGCP 507 

    Presentation date: 2008.08

  • 中国黒竜江省の非海成白亜紀前期鶏西盆の堆積作用とシーケンス層序

    日本地質学会第114年学術大会要旨 

    Presentation date: 2007.09

  • 統計学的経験則に基づく岩石風化の指標開発ならびに古気候解析への応用

    日本地質学会第114年学術大会要旨 

    Presentation date: 2007.09

  • Late Cretaceous accretionary Matoya Complex in the Shimanto North Belt, eastern Kii peninsula, Southwest Japa

    2nd Internation Symposium of the UNESCO-IGCP507 

    Presentation date: 2007.08

  • Statistical empirical index of chemical weathering: a new tool for evaluating the weathering intensity and paleoclimate

    2nd Internation Symposium of the UNESCO-IGCP507 

    Presentation date: 2007.08

  • Palynostratigraphy of the Lower Cretaceous Chengzihe Formation, Jixi Group of the eastern Heilongjian, northeast China

    2nd Internation Symposium of the UNESCO-IGCP507 

    Presentation date: 2007.08

  • Stable isotope stratigraphy of the non-marine Cretaceous Chengzihe Formation, NE China and the correlation

    2nd Internation Symposium of the UNESCO-IGCP507 

    Presentation date: 2007.08

  • 北海道天塩中川地域に分布する上部白亜系蝦夷超層群の砂岩モード組成:前弧海盆(空知−蝦夷帯)と海溝充填堆積物(日高帯)における後背地の共通性

    日本地質学会第112年学術大会要旨 

    Presentation date: 2006.09

  • Global correlation of the Lower Cretaceous Jixi Group, NE China by means of stable isotope stratigraphy

    17th International Sedimentological Congress 

    Presentation date: 2006.08

  • Assessment of chemical weathering and provenance of sediments based on a new ternary diagram with logcontrast principal component vertices

    17th International Sedimentological Congress 

    Presentation date: 2006.08

  • Sequence stratigraphy of the Early Cretaceous coal-bearing Jixi Group in Heilongijang Province, NE China

    17th International Sedimentological Congress 

    Presentation date: 2006.08

  • High-resolution stratigraphy of the non-marine Cretaceous in NE China: δ13C record of sedimentary organic matter for the Chengzihe Formation of the Jixi Group

    Second International Palaeontological Congress 

    Presentation date: 2006.06

  • アイチソン幾何学に基づく砂岩モード組成のトレンド解析

    日本地質学会第112年学術大会要旨 

    Presentation date: 2005.09

  • ポイントカウント法におけるデータ処理の問題点と是正法

    日本地質学会第112年学術大会要旨 

    Presentation date: 2005.09

  • 三重県南島町,四万十帯北帯の的矢コンプレックス

    日本地質学会第112年学術大会要旨 

    Presentation date: 2005.09

  • 因子分析による砕屑岩組成変化要因の特定

    日本地質学会第111年学術大会 

    Presentation date: 2004.09

  • Sedimentation and tectonics of the Yenchau Basin in north Vientnam

    5th International Symposium of IGCP434 

    Presentation date: 2003.10

  • 砕屑物組成データにおける定数和効果のlogratio法による査定

    日本地質学会第110年学術大会 

    Presentation date: 2003.09

  • 北ベトナム白亜紀堆積盆のテクトニクスとインドシナ変動

    日本地質学会第110年学術大会 

    Presentation date: 2003.09

  • 西九州海浦地域の黒瀬川構造帯,中・古生界層序の改訂とジュラ系葦北層群(新称)の層序

    日本地質学会第109年学術大会 

    Presentation date: 2002.09

  • Sandstone petrology and provenance of the Cretraceous sediments along the Amur River, Far East Russia

    4th Internationa Symposium of IGCP434 

    Presentation date: 2002.08

  • Examination of the Late Jurassic-Early Cretaceous subduction complexes along the Amur River: A new perspective on the accretionary terrane in Far East Russia

    4th Internationa Symposium of IGCP434 

    Presentation date: 2002.08

  • Radiolarians from the accretionary and forearc-basin facies, downstream of the Amur River, Far East Russia

    4th Internationa Symposium of IGCP434 

    Presentation date: 2002.08

  • 極東ロシア,アムール川下流域の付加体&#8211;前弧海盆堆積相より産する放散虫

    日本古生物学会2002年年会 

    Presentation date: 2002.07

  • 極東ロシア,アムール川下流域の付加体–前弧海盆堆積相より産する放散虫

    日本古生物学会2002年年会 

    Presentation date: 2002.07

  • Tectonics and sedimentary records of the Jurassic to Early Cretaceous basins in SW Japan

    International symposium, The 2002 Annual Meeting The Palaeontological Society of Japan 

    Presentation date: 2002.06

  • 九州黒瀬川構造帯田浦地域の小崎層から前期ジュラ紀アンモナイトの産出

    日本地質学会第108年学術大会 

    Presentation date: 2001.09

  • Geochemistry of Jurassic to earliest Cretaceous sequences of the

    3rd International Symposium of IGCP434 

    Presentation date: 2001.06

  • ジュラ〜白亜紀最前期豊浦・豊西層群の後背地変化

    日本地質学会第107年学術大会 

    Presentation date: 2000.09

  • Tectonic evolutional history of Jurassic to Earlt Cretaceous Nagato Basin, Inner Zone of SW Japan

    2nd International Symposium of IGCP434 

    Presentation date: 2000.06

  • J/K boundary of the Late Mesozoic forarc basins in East and South Asia

    2nd International Symposium of IGCP434 

    Presentation date: 2000.06

  • 田浦地域の豊西-川口岩石区の層序,堆積相と砂岩組成の吟味

    日本地質学会西日本支部第139回例会 

    Presentation date: 1999.12

  • 長門,黒瀬川構造帯のジュラ〜白亜紀最前期堆積盆の堆積シーケンスの発達と石英質砂岩の起源

    日本地質学会第106年学術大会 

    Presentation date: 1999.09

  • Tectonics, sedimentation and eustasy of the Jurassic and Cretaceous Systems in SW Japan

    1st international Symposium of IGCP434 

    Presentation date: 1999.06

  • 長門構造帯西部のジュラ紀・白亜紀堆積盆に関する2,3の新知見

    日本地質学会西日本支部第136回例会 

    Presentation date: 1998.12

  • Sedimentation and tectonics of the Jurassic to Cretaceous sutural forearc basins in SW Japan

    9th Regional Congress on Geology, Mineral and Engergy Resources of Southeast Asia (GEOSEA 98) 

    Presentation date: 1998.12

  • 豊浦・豊西層群の堆積相とジュラ〜白亜紀大陸縁辺層序

    日本地質学会第105年学術大会要旨 

    Presentation date: 1998.09

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Specific Research

  • 風化作用の定量化による,大量絶滅事変の解明:ベトナムの事例

    2020   Nguyen Quoc Dinh

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    北部ベトナム・Cao Bang省には、ペルム紀–三畳紀境界の石灰岩が露出しており、大量絶滅事変研究の好条件がそろっている。当初の研究計画では、Os・Sr同位体組成、後背地風化指標、鉱物組成の測定から、大量雑滅事変の要因追求を目指していたが、コロナ禍の影響で現地踏査がおこなえなかった。この代わりに、研究協力者であるDinh氏が現地踏査によって事前調査を実施した。申請者はこの研究期間中、炭酸塩岩用のXRF分析検量線作成と、炭酸塩岩標準試料を用いたICP-MSの前処理過程・分析のフローを構築した。研究費はこれらの事前研究に使用した。今後は、これらを利用して、試料採取と化学分析を実行する予定である。

  • 22億年前の全地球凍結の新たな証拠とその意義:巨大氷河の広がりと大気酸素の誕生

    2018  

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     本研究では,22億年前に発生したスノーボール・アース事変がインド北東部スィンブーム地塊においても記録されているのかを,土壌化学組成と,凍結亀裂と考えられる堆積構造の幾何学解析から検証した. 土壌化作用を風化指標W値で吟味したところ,22億年前は温暖湿潤気候から氷雪気候へ推移したことを示した.土壌亀裂の幅・深さ・間隔などは,現世の凍土に発生している凍結亀裂と幾何学的性質が一致した.したがって,堆積当時,永久凍土ないしは季節凍土が存在していた.今回の結果は,22億年前の寒冷化がインドにまで広がっており,真に全地球規模の寒冷化イベントが発生していたことを裏付けることになる.

  • 白亜紀における亜熱帯高圧帯の緯度方向シフト:地球温暖化に伴うハドレー循環の拡大と縮小

    2017   Higuchi taro, Mazmuder Rajat

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    The present study investigated the geochemistry and clay mineralogy ofmudstones collected from the lower to middle Cretaceous strata distributed inVietnam and Borneo island, in order to assess the paleoclimate. We found that mineralogical and geochemical differences that the presentsample bear are due the differences in the degree of hinterland weathering. Duringearly Cretaceous, Vietnam was exposed to a severe weathering environment, whilehinterland weathering almost halted in middle Cretaceous. As for Borneo, earlyCretaceous was a time of severe weathering, which slightly calmed in middleCretaceous. The reason for the decrease can be attributed to the aridification.Two new findings can beproposed by the present result. First,the area that undergone middle Cretaceous aridification was more extensive thanpreviously thought, reaching to Vietnam, and probably prevailed further to theequatorial region (Borneo). Secondly, note that Sichuan, Simao and Korat basinsare located in the continental interior, while the studied Vietnam and Borneoregion are located in the coastline of southeast Asia. Therefore, this suggeststhat the aridification is not due to the simple enhancement of the inland dryclimate, but more likely related to a major turnover in the climate system inmid-Cretaceous.

  • 20億年前の潮汐堆積物のウェブレット解析:太古地球の自転速度の解明

    2014  

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    インドに分布する20億年前の潮汐堆積物に対して、ウェブレット層厚周期解析をおこない、20億年前の地球自転速度と1年の日数を復元した。解析の結果、2.47、4.11、6.93、14.0、23.1、32.8のラミナ周期性が検知されたが、2.47から23.1のラミナ周期は突発的イベントを示していることがわかる。このことから、32.8が20億年前の大潮−小潮サイクルであると考えられる。よって、朔望月、恒星月あたりの太陽日は33.8、31.4日になる。この値から求められる20億年前の1年の日数は439日、1日の長さは20.0時間と算出される。

  • 楕円フーリエ解析による粒子形状の定量化と古波浪強度解析の新指標の提示

    2014  

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    石英粒子の形状をEF-PCA分析によって定量化し、堆積環境を識別する研究と、その形状指標から、有義波高などの波浪物性値を割り出す方法を開発した。前者の目標に関しては、粒子の巨視的な形状を記述する指標と微視的な形状を記述する指標の開発に成功した。そして、氷河、河川、風成、前浜の砂の堆積環境をある程度識別できた。しかしながら、形状指標値は同じ堆積環境でも地域間によって変動することもわかった。前浜の砂粒子では、指標値は波浪営力の強い順に指標値が増大した。この事実は、営力の増大に応じて指標値がすることを示している。この関係を利用すれば、粒子の形状から波浪強度や河川規模などが予知できると考えられる。

  • 現世土壌の化学組成に基づく古気候解析の新しい指標の提示

    2009  

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    本研究課題は,土壌の化学組成データから化学風化度の程度を,申請者が新たに開発したW値(8つの酸化物組成の主成分分析に基づく風化指標)によって抽出し,その土壌生成場の気候と化学組成の関係を解明することにある.さらに,この現世土壌データの解析結果を,古土壌の化学組成(XRF分析)に対して適応し,古気候解析の新たな指標を提示することにある. 前者の目的「気候帯が既知である現世土壌を分析して,気候を判別するW値の閾値を明らかにする」に関しては,1200個の土壌データの予察的解析を試みた.その結果,W値より気候を判定できることが判明した(Ohta et al., 2009a).しかし,温帯気候の土壌に関しては,気候判定精度が十分でない問題点も浮き彫りとなった.おそらくこの原因は,温帯気候帯が多様性に富むにもかかわらず,一括して解析した事に起因していると考えられる.この問題点解決のため,この研究期間中に,より細分化した気候帯(例えば,湿潤性大陸気候,大陸性混合林気候,地中海性気候,西岸海洋性気候など)を網羅したデータベースの作成に従事し,さらに総計2000個の土壌データを加算した. 後者の「古気候解析への応用」については,中国北東部に分布する前期白亜紀の堆積岩類への応用を試みた.この時代のこの地域は,鳥類・被子植物の祖先や原始的なほ乳類化石を産することから,生物進化学上,重要視されてきた.しかし,なぜこの地域のこの時期に爆発的な進化が起きたのかは不明であった.W値による解析の結果,爆発的な進化が起こった層準(時期)にW値が有意に上昇している事が判明した(太田ほか,2009;Ohta et al., 2009b).W値の上昇は気温の上昇や降雨量の上昇を意味する.したがって,爆発的進化の背景には,古動植物の繁栄をもたらすような気候の好転が関与していた可能性が明らかになった(太田ほか,2009;Ohta et al., 2009b). また,北海道の空知層群・蝦夷累層群に対してもW値の測定を行った(小林ほか,2009).前者と後者では後背地風化過程が大きく異なり,空知-蝦夷境界において,北海道における大きな地帯構造変動があったことが示唆されることが明らかになった(小林ほか,2009).

  • 淘汰作用による砕屑物組成の改変過程と源岩組成の復元

    2006  

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     本研究では,砕屑物の淘汰作用による組成変化を補正して,砕屑物の初生的な化学組成を復元する指標の提示を試みた.この特定課題の研究期間には,北海道天塩中川地域に分布する上部白亜系蝦夷超層群並びに熊本県田浦地域に分布するジュラ系葦北層群の砕屑岩試料の鉱物モード組成・化学組成の分析を行った. 両地域の砕屑岩試料とも淘汰作用による組成の改変を受けていることがわかった.細粒な砕屑岩試料ではAl2O3やK2Oなどが相対的に濃集していた.逆に,粗粒な砕屑岩試料ではSiO2やNa2Oなどの相対量が増大していた.これは,淘汰作用によって層状珪酸塩鉱物が細粒相に分離・濃集した結果を表していると考えられる.したがって,砕屑岩の化学組成データは,初生的な源岩の情報を保持していないことが明らかになった.そこで,本研究ではこの淘汰作用による鉱物・化学組成の改変過程を逆に利用し,組成変化の軌跡から源岩の組成を特定する手法を提唱する. 砕屑岩類は粒度・淘汰度を反映してSiO2/Al2O3¬―Na2O/K2Oダイアグラム上で線型に配列することがわかった.淘汰作用による組成変化はこの直線上の変動のみに集約されるので,源岩が同一であればすべての試料が同一直線上に配列する.しかし,源岩が異なる場合は,その化学組成に依存して回帰直線の傾きが変化することが判明した.さらに,この回帰直線の起点を求めることによって源岩の化学組成が復元できることが明らかとなった.すなわち,この判別ダイアグラム上では,回帰直線の傾きがおよそ0°の場合,砕屑物の源岩は堆積岩類であると判断できる.傾きが45°の場合は酸性火成岩類由来であり,90°に近い場合は塩基性火成岩類由来と判別できる. この研究成果によって,今後は源岩が不明な未知試料であっても,淘汰作用の影響を補正した上で,源岩の化学組成を議論できるようになった.

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Syllabus

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