岡山大学文明動態学研究所 Acta Medica Okayama 2436-8326 4 2025 吉備製鉄遺跡周辺地域の磁鉄鉱ざくろ石スカルン鉄鉱石の鉱物学的・地球化学的特徴 19 52 EN Yasushi TAKECHI Kurashiki Museum of Natural History Daisuke NAKAMURA Okayama University, Department of Earth Sciences Shigeyuki SUZUKI Okayama University, Department of Earth Sciences Joseph RYAN Okayama University, Research Institute for the Dynamics of Civilizations Takeshi UWAGAKI Okayama Prefectural Board of Education Masato NAGAHARA The Historical Study Group of Mining and Metallurgy of Japan Yuta YOSHIE Mitsui Mining & Smelting Co., Ltd. Kei IKEHATA University of Tsukuba, Faculty of Life and Environmental Sciences Osamu KIMURA Okayama University, Research Institute for the Dynamics of Civilizations Ryoichi HATTORI Osaka University, Graduate School of Humanities 論文 (Research article) 10.18926/67954 We conducted mineralogical and geochemical analysis of ore samples taken from locations surrounding the Jinmu, Sanpō, and Kōmoto mines in order to determine the source of iron ore uncovered from archaeological sites. The mineral composition of the magnetite-garnet bearing skarn deposits varies from mine to mine: while clinopyroxene and amphibole are present in the Jinmu and Sanpō samples, only a small amount of clinopyroxene occurs in the Kōmoto samples. The chemical compositions of magnetite and garnet are distinctive for each mine. Among the trace elements contained in the magnetite, Mg and Mn tend to be higher in the Kōmoto samples, Ti in the Jinmu samples, and Ca and Si in the Sanpō samples. The garnet from all the mines is andradite, but while the Kōmoto samples contain almost no Al, it is present in the Jinmu and Sanpō samples. Although samples were taken from a limited number of mine areas (three), our analysis provides an index for comparison with iron ore uncovered from archaeological sites, which will aid in provenance determination. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学科 Acta Medica Okayama 1340-7414 30 1 2024 A new insight into the driving mechanism for plate tectonics―the relationship between tectonic processes and the circumferential tensile forces associated with a rotating planet― 21 35 EN Robert MAURER Stuart HARKER Shigeyuki SUZUKI Allan WHEELER 10.18926/ESR/66846 　Mantle convection currents are the currently accepted driving force for plate tectonics that have ripped apart the continents and created oceans. Because of these actions, continental collisions and ocean closures have resulted. Our paper challenges the conventional concept and provides an alternate, mathematically justified drive mechanism. The pull-push motions of such convection currents in the upper mantle are here concluded to be too weak to be the driving mechanism.<br> 　Our proposal for such global scale forces concerns the effect of an offset centre of mass of the Earth that results in rotational wobbling. Kepler’s laws of planetary motion demonstrate the rotational behavior of the Earth to be aligned with the Sun on the outward and inward motions of the elliptical orbit. The unbalanced rotation on a fixed gravitational axis results in circumferential stresses on the outer Earth’s rim that is more than strong enough to pull the continental plates apart. The proposed unbalanced rotational stress force equation is shown to be sufficient to drive the cyclic breakup and reassembly of the continental plates, as well as the generation of new oceanic crust and subduction zones. Mantle convection currents are here demonstrated to have a passive rather than active role in the plate movements. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学科 Acta Medica Okayama 1340-7414 28 1 2022 岡山市北部吉備高原地域に分布する古第三系・新第三系の分布・堆積相と古地理変遷 1 25 EN Hajime Tanaka Seibu Engineering Consultants Co., Ltd. Shigeyuki Suzuki Department of Earth Sciences, Okayama University 10.18926/ESR/63514 No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 27 1 2021 新・古第三系の分布に着目した岡山県中西部における 吉備高原地域の地形特性 19 27 EN Hajime Tanaka Fukken Co., Ltd., Okayama branch office Shigeyuki Suzuki Graduate School of Natural Science and Technology, Okayama University 10.18926/ESR/61955 The Kibi Plateau Surface is associated with the Paleogene gravel river bed deposits of the Kibi Group and the Miocene marine deposits of the Katsuta Group and the Bihoku Group. These Paleogene and Miocene units are valley fill deposits. The Kibi Group is composed of formations which is deposited by more than 7 different depositional events during earliest to latest Paleogene Period. Repeated cycles of “erosion - formation of new valley system - deposition and fill up the valley” created the low relief topographic surface. The deposition of the Miocene deposits might complete the Kibi Plateau Surface. Detailed field works have done in middle western part of Okayama Prefecture. The Kibi Plateau Surface in study area is gently dipping from NW (about 600m high) to SE (about 100m high). The distributions of the Paleogene and Miocene deposits fit the surface. At the southern margin of the Kibi Plateau, the surface is a little inclined (from 400m high to 100m high) where the bottom of paleo-valleys of the Paleogene deposits are subparallel to the surface. It suggests that the gentle tilting of the Kibi Plateau is caused by an up-warping. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 26 1 2019 美咲町川北地域に分布する三郡変成岩から見出された片岩化した断層岩 19 24 EN Mirei MATSUSHITA Graduate School of Natural Science and Technology, Okayama University Shigeyuki SUZUKI Graduate School of Natural Science and Technology, Okayama University 10.18926/ESR/58575 The crystalline schist which is representatively exposed in the Innerside of Southwest Japan is called the Sangun Metamorphic Rocks (SMR). In Kawakita area, Misaki Town, Okayama Prefecture, schistose fault rocks which is newly described in below are intercalated in the SMR. The rocks are composed of lenticular fragments of pelitic, basic siliceous rocks and quartz vein with siliceous to pelitic matrix. The fine-grained muscovites which define schistosity penetrate the rocks. Major direction of layer which though to reflect slip plane is subparallel to the schistosity. The long axis of some fragments are slightly oblique to the schistosity. The combination of the two sets of planes is considered to be a composite planar fabric. These occurrences suggest that the rocks are fault rock before the Sangun Metamorphism and named as schistose fault rocks. Lenses of cataclasite and myronite are accompanied. Planar thin (about 10cm in thickness) brittle fault rock is also associated. These shear deformed rocks form units of layer (shear zone) of 10 to 100m in thickness, and are concordantly intercalated in the surrounded normal schists. Active periods of the shear zones had several times from before and after the event of the Sangun Metamorphism. No potential conflict of interest relevant to this article was reported.

岡山大学埋蔵文化財調査研究センター Acta Medica Okayama 2017 2019 岡山大学埋蔵文化財調査研究センター紀要2017 EN Takahiro Nozaki Archaeological Research Center, Okayama University Kentaro Minami Archaeological Research Center, Okayama University Etsuyo Yamamoto Archaeological Research Center, Okayama University Shigeyuki Suzuki Archaeological Research Center, Okayama University Yuji Yamaguchi Archaeological Research Center, Okayama University Shiho Iwasaki Archaeological Research Center, Okayama University No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 25 1 2018 U-Pb single grain zircon ages for Sanbagawa Metamorphic Rocks in central Shikoku (Japan): the Sanbagawa Belt re-united 39 48 EN Ulrich Knittel Clay and Interface Mineralogy, RWTH Aachen University Monika Walia Department of Geosciences, National Taiwan University Shigeyuki Suzuki Graduate School of Natural Science and Technology, Okayama University Yuan-Hsi Lee Department of Earth and Environmental Sciences, National Chung-Cheng University 10.18926/ESR/56695 The high-P/low-T Sanbagawa Metamorphic Belt that traverses SW Japan, has been subdivided into two belts thought to have been metamorphosed at ca. 120 Ma and at ca. 65 Ma (‘Sanbagawa Metamorphic Rocks’ and ‘Shimanto Metamorphic Rocks’). The subdivision was based on the assumption that metamorphism occurred at ca. 116 Ma, largely based on an early Rb-Sr isotope study and zircon data obtained for the eclogite unit of the Sanbagawa Belt, whereas in some parts of the belt detrital zircons of late Cretaceous age (90-80 Ma) were discovered. Analysis of detrital zircons sampled from two sites within the area considered to expose the older ‘Sanbagawa Metamorphic Rocks’, including the area investigated by the Rb-Sr study, reveals the presence of zircons younger than 95 Ma in all samples and some grains as young as 80 ± 4 Ma. It is therefore concluded that the Sanbagawa Belt is one single tectonic entity that formed in the Late Cretaceous though it contains older components, including fossiliferous clasts, older basic meta-volcanics and eclogite units that may record earlier metamorphic events. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 25 1 2018 A new method of terrace analysis to determine precise altitudes of former shoreline 31 38 EN Hideki Amano Graduate School of Natural Science and Technology, Okayama University Shigeyuki Suzuki Graduate School of Natural Science and Technology, Okayama University Masaru Sato Hanshin Consultants Co., Ltd., Makoto Yanagida Hanshin Consultants Co., Ltd., 10.18926/ESR/56694 The study area is situated in Japan Sea side margin of the Shakotan Peninsula, Hokkaido, Japan, where MIS5e Terrace is preserved along the cost. Numbers of tight drilling have done to establish new method for terrace analysis. Buried wave cut terrace and sea cliff (when the MIS5e Terrace was formed) are reconstructed by distribution of the terrace deposits and these bottom of unconformity planes. The precise site and altitude of former shoreline was also obtained. Altitudes of the former shoreline from the 7 sections are almost the same 22 to 27m in height. Previous data of the height of shoreline are obtained from the topographic MIS5e Terrace surface. The altitudes have variation from 30m to 60m. It suggests that the traditional method for the MIS5e terrace analysis had some errors in the study area. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 25 1 2018 福井県おおい町赤礁崎で見出された非石灰質ビーチロック 1 5 EN Shigeyuki Suzuki Graduate School of Natural Science and Technology, Okayama University Yoichi Azuma 平寺町松岡兼定島 4-1-1 ** Yasuyo Deyama 平寺町松岡兼定島 4-1-1 ** Hirokazu Yukawa Fukui Prefectural Dinosaur Museum Mayumi Usui Fujigakuin-Okayama 10.18926/ESR/56691 Beachrock which was formed about 0.5 meter higher than high tide is found in Akagurisaki, Ohi Town, Fukui Prefecture. The outcrops always get wet by spring water. The sediments are composed of well sorted rounded gravels and sands but calcareous shell is not found at all. Intergranular space is occupied by white amorphous cement. Magnesium and silicon rich composition of the cement is obtained by EPMA analysis. There is a conjecture that the magnesium rich cement was precipitated in spite of solution of calcareous shell under saturated state by spring water, because calcium has a higher tendency to ionize than magnesium. No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 2018 縄文時代の海岸線復元と遺跡動態 : 岡山平野のボーリング調査を踏まえて 1 7 EN Etsuyo Yamamoto Archaeological Research Center, Okayama University Yuji Yamaguchi Archaeological Research Center, Okayama University Shigeyuki Suzuki 瀬戸内沿岸における縄文時代の人間活動を理解するためには、古地形復元と遺跡動態との関連を分析することが重要な視点となる。その第一歩として、同地域で有数の縄文遺跡密集地である岡山平野において、ボーリングコアを採取する調査を実施し、その地質調査から、特に海岸線に現れる環境変化の復元を試みた。その結果、縄文海進のピーク以降も、相対的な海水準変動が海岸線の変化をもたらし、人間活動に影響を与えた可能性が、遺跡動態の検討からも予想されることとなった。 No potential conflict of interest relevant to this article was reported.

岡山大学埋蔵文化財調査研究センター Acta Medica Okayama 2016 2018 岡山大学埋蔵文化財調査研究センター紀要2016 EN Yuji Yamaguchi Archaeological Research Center, Okayama University Etsuyo Yamamoto Archaeological Research Center, Okayama University Shigeyuki Suzuki Graduate School of Natural Science and Technology, Okayama University Shiho Iwasaki Archaeological Research Center, Okayama University Kentaro Minami Archaeological Research Center, Okayama University Takahiro Nozaki Archaeological Research Center, Okayama University No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 23 1 2016 Prelithification shear structures of mélange unit in Shiofuki-iwa area, the upper Cretaceous Shimanto Belt, Wakayama Prefecture, Japan 9 15 EN Norito Takesue Graduate School of Natural Science and Technology, Okayama University Shigeyuki Suzuki Graduate School of Natural Science and Technology, Okayama University 10.18926/ESR/55322 Analyzing of sedimentary facies and structure together with regional field mapping were studied in the mélange unit, upper Cretaceous Shimanto Belt, Wakayama Pref., SW Japan. The field survey was concentrated in the coast of Shiofuki-iwa, Miyama Complex, Hidakagawa Belt where soft deformations penetrate throughout the mélange unit. Brittle to ductile faults associated as later deformations are excluded. The mélange unit is subdivided into the Y-shear zone (YSZ) and P-foliation zone (PFZ). The YSZ is composed of thick lenticular sandstone (trends subparallel to the direction of the mélange), intense shear band (thin layer with concentrated prelithification shear deformation) and mudstone dominant mélange. The PFZ is composed of mudstone dominant mélange (associated with foliations which slightly oblique to the direction of the YSZ) and lenticular sandstone (slightly oblique to the direction of the YSZ). The intense shear band separates the YSZ and PFZ. Preserved radiolarian fossils free from deformation in the intense shear band is the evidence of the prelithification shear deformation in the mélange. A remarkable-fact is that the structures of mélange unit are formed under sinistral sense of shear. The mélange unit in the Shiofuki-iwa is ascribed to be formed by sinistral sense of shear during sediments were prelithified. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 23 1 2016 航空レーザ傾斜量図を用いた斜面・土石流危険箇所抽出の試み 1 7 EN Shigeyuki Suzuki Graduate School of Natural Science and Technology, Okayama University Masashi Miyashita WESCO co. Takeshi Hirakawa WESCO co. Mieko Fujiwara WESCO co. Satoshi Nishiyama Graduate School of Environmental and Life Science, Okayama University 10.18926/ESR/55321 The slope gradation map which is obtained from airborne laser scanning is very important tool to detect hazardous sites of landslide, debris flow and others. The features of the images (what the images are represented) in the map were confirmed by field survey. The study area, Tamagashi is situated in the Kibi Plateau area, Okayama City, Japan. The map helps to distinguish between artificial microrelief and natural microtopography very well. Small scarps (even 0.5m high), rocky cliffs and large blocks (larger than 2m) are identified in the map. The detail images of the microrelief suggest threatening sites. The merit of the map leads us to find the site in the field easily. We will not miss the threatening sites by using the map. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 22 1 2015 岡山県川上町地頭地域における上部三畳系成羽層群地頭層の層相解析 31 39 EN Yuto Masaoka Shigeyuki Suzuki 10.18926/ESR/54119 Facies analysis and analysis of stratigraphy together with folded structure of the Norian Jito Formation were studied in Jito Area, Kawakami, Okayama Pref., SW Japan. Results of regional mapping and measured sections reconstruct three-dimensionally distribution of the Jito Formation. The Jito Formation is sub-divided into the four new members; the Shimohira Muddy Sandstone Member, the Otofuji Coarse-grained Turbidite Member, the Misawa Fine-grained Turbidaite Member, and the Ide Conglomerate Sandstone Member in ascending order. The shimohira Muddy Sandstone Member is interpreted to be deposited in an inner-bay. The Otofuji Coarse-grained Turbidite Member and The Misawa Fine-grained Turbidite Member are considered to be deposited on a continental shelf. The Ide Conglomerate Sandstone Member is inferred to be a shallow marine deposit. As a result, the Jito Formation is regarded as one transgressive-regressive package. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 22 1 2015 備前国分寺礎石の岩石特徴と産地の推定 25 30 EN Shigeyuki Suzuki Norihide Nishimura Yuji Ariga 10.18926/ESR/54117 The Bizen Kokubunji Temple was constructed in the 8th century, in Maya, Akaiwa City, Okayama. Only foundation stones are preserved. Geological characteristics of the foundation stones suggest that they are collected from mountain area of Maya, about 300 to 800m west from the site. The similarity of the foundation stones and the rocks Maya are identified by the following characteristics. 1) Assemblage of rock types (high grade welded tuff breccia, tuff breccia, tuffaceous sandstone and conglomerate) are the same. 2) Lithology of the 3 rock type of the foundation stones and the rocks from Maya are the same. 3) Rheomorphic flow structures are developed in both high grade welded tuff breccia. 4)Mudstone fragments are contained in both high grade welded tuff breccia tuff breccia. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 21 1 2014 岡山県美咲町小原周辺に分布する中部中新統からのPaleoparadoxiaの産出報告 7 11 EN Akira Fukuchi Shigeyuki Suzuki 10.18926/ESR/53193 　The partially preserved left humerus of the Desmostylia (Mammalia) has been collected from the riverbed in Obara, Misaki-cho, Okayama Prefecture in the western Japan. This specimen can be classified to the genus Paleoparadoxia by the following features: the absence of the supratrochlear foramen; the curved disto-lateral border of the shaft in the antero-posterior view; the medio-laterally expanded flat trochlea of humerus. Moreover, this specimen can be referred to cf. P. media on the basis of its middle-sized dimensions. This is the second occurrence of Palaeoparadoxia from Okayama Prefecture. No potential conflict of interest relevant to this article was reported.

岡山大学環境管理センター Acta Medica Okayama 0917-1533 35 2014 活断層調査の方法と断層活動の特徴 8 13 EN No potential conflict of interest relevant to this article was reported.

岡山大学埋蔵文化財調査研究センター Acta Medica Okayama 2012 2013 岡山大学埋蔵文化財調査研究センター紀要2012 EN No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 20 1 2013 岡山県新見市の中新世備北層群からのPeriploma mitsuganoense Araki (Bivalvia: Mollusca)について　―特にその古地理学的意義― 7 11 EN Eiji Taguchci Shingo Kishimoto Shigeyuki Suzuki 10.18926/ESR/52165 In this paper, we deal with re-description of Periploma mitsuganoense Araki and it’s morphological variation and significance of the molluscan fauna of it from the Miocene Bihoku Group in Niimi City, Okayama Prefecture, Southwest Japan. Moreover, the paleogeographic significance of this species is analyzed. The obtained results are summarized as follows: 1. The morphological variation of Periploma mitsuganoense Araki has a wide range on the basis of the analysis of the morphological outline. 2. The occurrence of P. mitsuganoense Araki from the Pectinid fauna is the first record in the West Setouchi Geological Province. 3. It is presumable that P. mitsuganoense Araki is an endemic species in the First Setouchi Geological Province from a view point of it’s spatial distribution. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 20 1 2013 岡山県倉敷市北村地域で発生した土石流災害の特徴と要因 1 6 EN Yuki Kimura Shigeyuki Suzuki 10.18926/ESR/52164 The debris avalanche occurred in Kitamura area, Kurashiki City, Okayama Prefecture caused by the hard rain of Typhoon 12 of September, 2011. Furthermore, 11 small landslides occurred in the study area. In this area, the altitude of mountainous are not so high (150m to 250m) and the amount of precipitation which producted the debris avalanche was not very serious quantity with 230mm. However the debris avalanche occurred. One private house collapsed, and the first floor part of the Kitamura Elementary School was buried due to the debris flow. The purpose of this study is to examine causes of the debris avalanche disaster occurred in Kitamura area using applied geological technique. The length of the debris avalanche scar is about 250m, and alluvial fan is formed as a debris slope. The ground is composed of weathered granite and the bottom of the valley was filled by soils derived from disintegrated granite. There are three small landslides as head scarps with steep slopes at approximately 30°-35°. The debris avalanche was inferred to have started as a shallow soil slip at the head by rainfall. 3 major causes are inferred which originated the debris avalanche in the study area; steep slope, ground composed of weathered granite, existence of sandy soil which occupied at the bottom of valley. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 19 1 2012 上部三畳系成羽層群における 日本最古の化石林の発見 ―堆積環境復元および古植生復元における意義― 25 37 EN Hirokazu Yukawa Kazuo Terada Ge Sun Shigeyuki Suzuki 10.18926/ESR/49211 Erect fossil stumps were found from the outcrop of the Upper Triassic Hinabata Formation, the uppermost part of the Nariwa Group at Hinabata, Nariwa-cho,Takahashi City, Okayama Prefecture, SW Japan. They are evidence of the oldest fossil forest in Japan. The Upper Triassic Nariwa Group is mostly composed of non-marine deposits except the marine Jito Formation and characterized by the abundance in plant fossils. The marine Jito Formation is characterized by occurrence of Norian Monotis ochotica. On the basis of detailed observation of the occurrence of erect fossil stumps, as well as sedimentary facies of fossil-bearing unit, the fossil forest was interpreted to have grown on the top of the natural-levee units. One of the erect fossil stumps was identified as Xenoxylon sp. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 19 1 2012 秋吉帯高山石灰岩層群の褶曲構造 5 11 EN Noriyuki Inada Shigeyuki Suzuki Keisuke Ishida 10.18926/ESR/49208 The fold structure of the Akiyoshi Belt was analyzed in Kawakami-cho, Okayama Prefecture, where the Lower Carboniferous to Middle Permian Ko-yama Limestone Group (Yokoyama et al., 1979), Permian Yoshii Group (Sano et al., 1987) and Triassic Nariwa Group (Teraoka, 1959) are distributed. The Nariwa Group unconformably covers the Paleozoic successions (Otoh, 1985). The Lower Carboniferous to Middle Permian Ko-yama Limestone Group, dated by foraminifers and fusulinids (Yokoyama et al., 1979), is mainly composed of massive limestone with basic volcanics, acidic tuff and chert. The Paleozoic successions of the Akiyoshi Belt were folded during the Middle to Late Permian (Suzuki et al., 1990). Strata of the Ko-yama Limestone Group generally strike E-W and dip to the north. The Hoya section about 300 m thick is composed of limestone, basic tuff, chert and acidic tuff, limestone, basic lava and tuff in ascending order. In this section, Ishida et al. (2012) recognized a nearly complete conodont faunal succession ranging from the upper Visean to the lower Moscovian. The faunal succession indicates younging southward, and the strata are overturned. A folded strucuture of tight overfold with north-dipping axial plane was reconstructed. Similar style of small scale overfolds of banded chert and turbidite were observed in the overlying Yoshii Group. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 19 1 2012 岡山平野の泥炭層から推測される完新世の海水準変動と古環境変遷 1 4 EN Shigeyuki Suzuki 10.18926/ESR/49207 Quaternary peat beds from bore-hole samples deliver information to reconstruct paleoenvironment. Altitudes of dated non-marine peat beds and marine beds allow to be created a sea-level curve. 4 peat beds (A to D) are identified from the uppermost Pleistocene to Holocene deposits of the Okayama Plain. They thought to be deposited at stable events during sea-level change. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 18 1 2011 岡山市北部吉備高原地域における地形区分―斜面防災のための試み― 5 10 EN Shigeyuki Suzuki Yuna Omizo Minoru Hirata Makoto Nishigaki 10.18926/ESR/47747 The Kibi Plateau is characterized by horizontal skylines and they are considered to be an uplifted peneplain. Landform of the plateaus in central part of Okayama Prefecture is divided into "Kibi plateau landform" and "Recent dissecting landform". The Kibi plateau landform is composed of low relief surface and relict mountain. The altitude of the low relief surface varies from 300 to 450m in Kayo area, and 200 to 350m in Kanayama area. The Recent dissecting landform is characterized by escarpment and cuts the Kibi plateau landform. Knick-point is formed at the boundary between two landforms and steep slope is distributed just below the knick-point. The steep slope of the recent dissecting landform is unstable and a potential of landslide is high. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 16 1 2009 Provenance of Early Cretaceous Hayama Formation, Okayama Prefecture, Inner Zone of Southwest Japan: constraints from modal mineralogy and mineral chemistry of derived detrital grains 29 42 EN Daniel K. Asiedu Shigeyuki Suzuki Tsugio Shibata 10.18926/ESR/19850 Petrographic and phase chemistry studies of detrital grains were carried out on sandstones from the Lower Cretaceous Hayama Formation, Inner Zone of Southwest Japan, to determine their provenance and the tectonic setting during the early Cretaceous. The results of the modal mineralogy suggest that the Hayama Formation has magmatic arc provenance and that deposition of the sediments took place in the back-arc areas with detritus mostly derived from the magmatic arc and rifted continental margins. The chemical compositions of chromian spinel, chlorite and sphene indicate that significant proportions of the detrital grains were derived from mafic and/or ultramafic sources. The source areas are the mafic and ophiolitic rocks in the Sangun-Renge and Akiyoshi terranes and the felsic volcanic rocks probably from either the Akiyoshi terrane or a source not presently exposed in southwest Japan. However, minor amounts of the detritus were derived from the basement rocks; i.e., carbonates and siliciclastic rocks of the Akiyoshi terrane and the metamorphosed mafic rocks of the Chizu terrane. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 16 1 2009 日本最初の用語「地質学」の成立: 箕作阮甫（1799-1863）の貢献 1 7 EN Hakuyu Okada Shigeyuki Suzuki 10.18926/ESR/19848 The first Japanese word "chishitsu-gaku" for the "geology" was proposed by Genpo Mitsukuri, a scientific contributor in the Tokugawa regime in the 19th century, who was born in 1799 in Tsuyama in Western Honshu, Japan and had worked for scientific activities of the Tokugawa government from 1839 to 1863. His major works for the first making of the "chishitsu-gaku" for the "geology" have been presented in this paper, also showing his contribution to Japanese sciences. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 15 1 2009 現世土壌の岩石学的記載　：　古土壌研究への応用の一例 9 32 EN Shigeyuki Suzuki 10.18926/ESR/15024 The microscopic observations of the recent soil horizons were conducted in Okayama, Japan (moderate climate). The several soil horizons, including two surface (epipedon) and three subsurface horizons, were recognized in the forest, poorly vegetated hill, and riverside around the Okayama University. The umbric epipedon can be segregated from the organic-rich subsurface horizons by the scattered organic materials in thin sections. The ochrich epipedon shows the sandy matrix without any cements and the illuviation of clay minerals. The subsurface horizons identified in the study area are as follows: albic, argillic, and cambic horizons. Each subsurface horizon shows the specific structures in thin sections. The albic horizon is characterized by the absence of the illuviation. The argillic horizon definitely shows the clayey matrix and the illuviation of clay minerals. The primary structures may be retained in the cambic horizon. The microscopic examination of the Miocene paleosols from the Ukan-cho, Okayama, was attempted. By comparing the recent soils, the cambic horizon and spodic horizon, which is characterized by the concentration of sesquioxides, are identified in the paleosols. This attempt suggests that the microscopic observations of the recent soils is a useful guide to understanding the paleosols No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 15 1 2009 岡山市北部の舞鶴帯から産出した二枚貝・巻貝化石 1 8 EN Keiji Nakazawa Shigeyuki Suzuki Hideto Uwada 10.18926/ESR/15022 Permian and Triassic molluscan fossils are found from Mitsu-area, Okayama City, Southwest Japan. Permian bivalve and gastropod fossils are collected from mudstones of the Upper Formation of the Maizuru Group. 4 species of bivalves (Nuculopsis? sp. ind., Leptodesma sp. ind., Streblopteria cf. eichwaldi, Posidonia sp. ind.) and 5 species of gastropods (Worthenia cf. corrugata, Callitomaria n. sp. cf. stanislavi, Apachella n. sp. ind., ??Eunemopsis like trochid, ??Yunnania sp.) are identified. Lower Triassic bivalve fossils are collected from sandstones of the Oono Formation. Neoschizodus cf. laevigatus and Bakevellia (Maizuria) kambei are identified. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 1 1 1994 Gradational development of slaty cleavage to schistosity -an example from the Iberian Pyrite Belt, Spain- 9 18 EN shigeyuki Suzuki 10.18926/ESR/13953 The Iberian Pyrite Belt is an Upper Paleozoic succession which has been divided into the Phyllite-Quartzite Group, the Volcanic-Sliceous Complex and the Culm Group in ascending order from base to the top. The contacts among them are conformable. These Groups are tightly folded and metamorphosed un-der low-grade conditions during Hercynian times. The first stage folds of the Volcanic-Siliceous Complex and the Culm Group are associate with slaty cleavages (S1), while the Phyllite-Quartzite Group is asso-ciate with schistosities (S1). Fold analysis using cleavages and minoe folds has been utilized in the analysis of the stratigraphy. This led to systematic horizontal collection of specimens (pelitic rocks). S1 texture is defined by paralled alignment of secondary platy minerals which tend to grow larger and together, forming zonal domains toward the Phyllite-Quartzite Group. The clay matrices change to recrystallized quartz toward the Phyllite Quartzite Group. Textural modifications are evidenced by gradational changes from slaty cleavages to schistosities. This shows that recrystallization is the important deformation mecha-nism responsible for S1 development. It also reflects that the deformation was contemporaneous with metamorphism. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 2 1 1995 水中テレビロボットによる瀬戸内海での海底地質調査 13 22 EN Shigeyuki Suzuki Takashi Inada 10.18926/ESR/13940 Submarine geological survey using the remotely operated TV vehicle (RV100), was carried out in 4 offshores of the Seto Inland Sea in Kagawa Prefecture. The study areas are west of Kosei Island of Sakaide City, south of Okado-bana of Nankai Town, west of Misaki of Takuma Town and north of Nou-Misaki of Sakaide City. TV vehicle transmite clear pictures of bottom of the sea to the monitor on board. The submarine geology of the study areas are composed of Cretaceous granitic basements and Quaternary sedimentary covers. By using these pictures Recent and Pleistocene deposits could be distinguished and lithology of sediments could also be identified. Lithology of sediments was however difficult to identify using the usual sonic prospecting method. Furthermore, pictures suggesting that ripples are just forming have been obtained. The TV vehicle is convenient in submarine survry, because it can travel much longeer and deeper than human diver. A new method of mapping submarine geology using TV vehicle was developed. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 3 1 1996 Paleogene talus deposits, Okayama City, Southwest Japan 17 24 EN Shigeyuki Suzuki 10.18926/ESR/13928 In eastern Chugoku area, Paleogene deposits have not been recognized until fission-track dating of so called "Mountain Gravels" was carried out (Suzuki et al. 1995). Two sedimentation events in Paleogene time (27Ma and 34-35Ma) are inferred by the F-T dating Major lithology of the Paleogene deposits in the study area is graved which is mainly composed of subrounded to rounded cobbles. The "Mountain Gravels" were previously thought to be lower Quaternary deposits. The "Mountain Gravels" is associsted with coal bearing mud, sand, gravel and breccia deposits. The breccia deposits is distributed sporadically between the "Mountain Gravels" and basement rocks. The deposits are mainly composed of poorly sorted breccia and associated granitic sands. It is inferred that the breccia deposits are talus deposits. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 3 1 1996 Provenance of Lower Cretaceous sediments in the Nariwa and Hokubo areas, Okayama Prefecture, deduced from detrital modes and geochemistry of sandstones 1 16 EN Shigeyuki Suzuki Tsugio Shibata 10.18926/ESR/13927 Petrographic and geochemical study of sandstones from the Kenseki Formation have shown that the sandstones are compositionally immature. The immaturity is reflected geochemically by their low SiO2 contents (52-66 wt%) and petrographically by low modal percents of quartz and K-feldspar, and high modal percents of plagioclase and volcanic lithic fragmants. The Kensaki sandstones are, however, poor in Na2O (up to 2.1 wt%). Both petrography and geochemistry suggest a heterogeneous source lithologies of acidic and basic volcanics, sedimentary, and ultramafic rocks. Petrographic evidence is supplied by quartz and plagioclase of volcanic origin, acidic volcanic fragments, basic volcanic fragments, volcanic glass, serpentinite fragments and detrital spinel grains. Geochemical evidence is provided by high FeO* (total iron as FeO), MgO, TiO2, CaO and K2O contents. Petrographic and geochemical study of the Kenseki sandstones indicate calc-alkaline oceanic island are provenance. The sediments were locally derived, with Alpine-type ultramafic rocks exposed in the north and volcanic materials of the Akiyoshi Belt supplying the bulk of the detritus. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 4 1 1997 三畳系成羽層群の地質と地すべり 21 32 EN Shu Hotani Shigeyuki Suzuki Hajime Tanaka Takuya Yamada 10.18926/ESR/13916 Geological and topographical study of landslides in the Triassic Nariwa Group has been carried out. Nariwa Group is mostly composed of non-marine deposites and is characterized by cycle of fining upward successions. Landslides abundantly occur in the non-marine successions. Slip surface occure in coaly mudstones that have conspicuously less strength than sandstones. Creeps immediately below slip surfaces contribute to the occurrence of landslides in the Nariwa Group. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 5 1 1998 児島湾干拓地におけるボーリング試料から得られた(14)C年代測定値 13 16 EN Hajime Sasaki Shigeyuki Suzuki 10.18926/ESR/13911 Two 14C ages are obtained from drilled core samples in Kojima Lake area. One is 7920±250 y.B.P. from peat which is just below silty clay of bay sediments (-14.30-14.61 m) The other is 24900+3450,-2450 y.B.P. from pale milky gray clay of fluvial sediments (-24.15-24.45 m). No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 5 1 1998 横浜町に発達する段丘に地形と堆積物 1 12 EN Shigeyuki Suzuki Akiko Miyawaki 10.18926/ESR/13909 Higher, middle and Lower Terraces (Quaternary) have been distinguished in Yokohama Town, Aomori Prefecture. The Higher Terraces are subdivided into three terraces, H1,H2 and H3. They are distributed in hills. H1 and H2 deposites are composed of gravels of fan deposits. H3 deposits are composed of gravels, sands and mud of alluvial plain deposits. The Middle Terraces are subdivided into three terraces, M1, M1' and M2, and occupy almost all terraces in Yokohama Town. These deposits are composed of beach (sand with gravel) and fan (gravel) deposits. The Lower Terraces are subdivided into two terraces, L1 and L2. The L1 Terrace is distributed in limited area along coast and thought to be composed of beach deposits. The L2 Terrace is distributed in limited area along river and composed of braided stream deposits. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 6 1 1999 玉野市出崎海岸に露出した縄文時代の泥炭層 23 28 EN Shigeyuki Suzuki Koichi Yukimoto 10.18926/ESR/13906 Peat bed remains isolated in the shoreline of western beach of Desaki peninsula. Collected samples gave radiocarbon data of 5790±80 and 5810±60 years BP. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 7 1 2000 A New Species of Lithostrotion (Siphonodendron)(Rugosa) from the Hina Limestone, Okayama Prefecture, Southwest Japan 47 50 EN Shigeyuki Suzuki 10.18926/ESR/13902 A new rugose coral species, Lithostrotion (Siphonodendron) hinensis is described in this paper. It was collected from the Carboniferous Hina limestone in Okayama Prefecture, Southwest Japan. Judging from the paleontological data, the age indicates probably Late Viaean, Early Carboniferous. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 7 1 2000 岡山県井原市浪形の標高240mの石灰岩に残された海食地形 41 46 EN Takao Fujiwara Shigeyuki Suzuki Yasuo Maeda 10.18926/ESR/13901 The tidal notch and the sea caves which cut into the Namigata Limestone is stiuated in 240m above sea level, Ibara City. The notch assocciates the Namigata Terrace 200m to 240m high. These geomorphological features indicate an event of high sea level. However the age of the event has not been known. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 7 1 2000 岡山市北部, 備前, 富原炭鉱の夾炭層と「山砂利層」との関係 35 40 EN Shigeyuki Suzuki Keiji Nakazawa Hajime Tanaka 10.18926/ESR/13900 The Bizen and Tomihara Coalfields which were situated in northern Okayama City, had produced lignite during 1940s. Distribution of coal measures indicates that the coal measures are intercalated in the middle of the so-called "Mountain Gravels". The "Mountain Gravels" is subdivided into two formations ; the older, about 34〜35Ma, and the younger, about 27Ma, of fission track ages. The older formation inculudes the Bizen Coal Measures. On the other hand, the Tomihara Coal Measures are intercalated in the younger formation. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 8 1 2001 四国東部, 美馬町地域の中央構造線 13 28 EN Yoshinobu Mizui Toru Tachibana shigeyuki Suzuki 10.18926/ESR/13887 Tracing outcrops of shear zone were used to describe the geometry and structure of the Median Tectonic Line in Mima area, eastrn Shikoku. A distinct new fault outcrop was discovered between the Mino and Ikuchi Faults at the northern slope of the Mt. Boso. These two faults are regarded as a single continuous fault. The analysis of surface fabrics of quartz in fault in fault gauge has been carried out to determine relative fault activity events. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 8 1 2001 有漢町に分布する中新統有漢累層 1 12 EN Takao Fujiwara Eiji Taguchi shigeyuki Suzuki 10.18926/ESR/13885 In this paper, we deal with the Miocene Ukan Formation, sporadically distributed in Ukan-cho, Okayama prefecture, from a viewpoint of analysis of lithology and molluscan assemblages. The Ukan Formation is lithostratigraphically divided into the Suzuoka Conglomerate, Yamagata Muddy Sandstone, Shimoyokomi Sandstone and Conglomerate, Azechi Sandstone and Conglomerate, Tsuneyama Siltstone Members in ascending order. The following 6 molluscan assemblages are recognized. The lower four members and the last member is correlative to the Lower Sandstone and Upper Shale Formation of the Bihoku Group, respectively judging from lithology and fauna. The temporal chages of the above mentioned molluscan assemblages represents that gradual deeping of sea during the depositional period from the Suzuoka Conglomerate and Yamagata Muddy Sandstone Members to the Azechi Sandstone and Conglomerate Member via the Shimoyokomi Sandstone and Conglomerate Member, and abrupt deeping of sea seems to have happened between the Azechi Sandstone and Conglomerate Member and the Tsuneyame Siltstone Member. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 9 1 2002 傾斜区分図と第三紀層の分布でみた吉備高原の地形発達史 25 30 EN Takao Fujiwara Shigeyuki Suzuki A peneplain is evident in Takahashi area from slope map presented in this paper. The map shows that older gentle valleys exist in the Kibi Plateau. Miocene marine deposits are colored on the slope map. The Miocene marine deposits mostly distribute along the older valleys. The distribution of the Paleogene gravel river deposits is not cintrolled by topography. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 9 1 2002 京都府宇治田原町の丹波帯泥質岩のストレート劈開に沿って産出する黄鉄鉱スポットについて 19 24 EN Teiji Mikami Makoto Musashino shigeyuki Suzuki 10.18926/ESR/13880 Pyrite spots were identified in pelitic rocks from the Ujitawara area, southernmost part of Tamba belt. XMA analysis shows that the spots are composed of pyrite. The spots occur along slaty cleavage plane and form spotted shape of diameter of about 5mm. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 10 1 2003 津山盆地東部に分布する中新統勝田層群の堆積環境 23 31 EN Ryo Yamasaki Shigeyuki Suzuki 10.18926/ESR/13875 The Miocene Katauta Group of the Syohoku-cho area is subdivides into 6 members ; The Uetsuki Conglomerate Member, Nara Sandy Mudstone Member, Tai Gravelly Sandstone Member, Takatori Conglomerate Member, Ayabe Mudstone Member and Maruyama Mutstone Member from bottom to top. The unconformity between Miocene deposits and basement rocks in this area was traced to obtain geometry of the Miocene basin. Contour maps of the bases of the Miocene Yoshino Formation and Takakura Formation indicate paleo-topography. The obtained topography demonstrates a valley, which flowed to north-west, and a few islands and bays. It indicates that these Miocene successuions were deposited in the topography which resemble to the present Seto Inland. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 10 1 2003 吉備高原周辺の古第三系に関する最近の知見とその古地理学的意義 15 22 EN Hajime Tanaka Shigeyuki Suzuki Shu Hotani Yasuo Yamamoto Tohru Danhara 10.18926/ESR/13874 The "Kibi Plateau" forms a unique geomorphic province with the gently-sloping and stable continental feature. Gravel deposites called the "Mountain Gravels", are distributed sporadically in the Kibi Plateau, and have been considered Pliocene deposits. However, recent fission-track ages of the tuff beds intercalated in the deposits have indicated that the ago of deposits are Paleogen in the age. So far, fission-track ages (using zircon) of 61 to 65, 55, 37, 34 to 35 and 27 Ma are obtained. Remaining the belt-like distributions of the Paleogene gravelly valley-full deposits suggest that the Kibe Plateau has been keeping as a stable block, and repeated periods of incision followed by sedimentation of valley-fill deposits are occurred in the area during Paleogene period. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 11 1 2004 岡山県玉野市出崎海岸に埋没する完新世中期の泥炭層の古環境解析 39 47 EN Mariko Matsushita Hiroshi Sato Shigeyuki Suzuki Koichi Yukumoto Arata Momohara Yayoi Ueda Shigehiro Katoh Yasuo Maeda 10.18926/ESR/13870 The buried peat deposit was foud in the sand beach on the Desaki coast (Tamano City, Okayama Prefecture), the northeastern coast of Seto Inland Sea. In this study, we performed sulfur and diatom analyses of the deposit. The results were used along with 14C dates and the eruption age (7300 cal BP) of Kikai-Akahoya tephra (K-Ab) to derive sedimentary environments of the deposit. K-Ah was detected just below the peat deposit. At the culmination of the Jomon transgression, the peat deposit had been formed in brackish environments of salt marsh for about 300 years. In order to reconstruct local paleovegetation, we analyzed pollen, wood and plant fossils in the deposit. The results show vegetational transition from a deciduous broadleaved forest mainly of Ouercus subgen. Lepidobalanus to Pinus forest. In spite of the Holocene thermal optimum, the vegetation dominated by Ouercus subgen. Cyclobanopsis was not recognized at the Desaki site, as has been shown in many other regions of regions of western Japan. Ouercus sect. Prinus was replaced by Ouercus sect. Aegilops as the dominant section of Ouercus subgen. Lepidobalanus, suggesting early establishment of traditional rural vegetation of 'Satoyama' in Japan. However, no evidence for human agency has been obtained from the mid-Holocene archaeological sites around the Desaki site. Thus it is more likely that this vegetational transition resulted from the succession caused by natural forces such as ecological disturbance and climatic and/or endemic situations rather than by cultural deforestation. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 11 1 2004 岡山平野における最終氷期最盛期以降の海水準変動 33 37 EN Shigeyuki Suzuki 10.18926/ESR/13869 Postglacial relative sea-level change of the Okayama Plain Area has been analyzed. Former sea-levels were recognized by using peat beds and marine organisms which are also available for 14C dating. Peat beds were rhought to be formed under a stable sea-level condition. 14C ages of the analyzed peat beds were seprated by 4 groups ; 30〜18 ka BP, 11〜8 ka BP, 6〜4 ka BP and 3〜2.5 ka BP, indicate 4 stable sea-level periods. 2 transgressive events (18〜11 ka BP and 8〜6 ka BP) and one regressive event (3.5?〜3 ka BP) were also inferred. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 13 1 2006 倉敷市水島地域の沖積地盤地質 15 18 EN Shigeyuki Suzuki 10.18926/ESR/13847 The study srea, Mizushima is occupied by polder and reclaimed land. The ground of this area is composed of the Holocene deposits below the surface. The deposits are mostly 10 to 20m in thickness and composed of 2 units, the B Unit and C&D Unit. The B Unit is composed of muddy sand with 2 to 3m in thickness. This unit is thought to be deposited in the mouth of paleoriver. The C&D Unit is composed of marine mud and sand with 10 to 15m in thickness. This unit is especially soft and will expand ground oscillations during an earthquake. No potential conflict of interest relevant to this article was reported.

岡山大学理学部地球科学教室 Acta Medica Okayama 1340-7414 13 1 2006 A Review on the Quaternary Characteristics of Pleistocene Tracts of Bangladesh 1 13 EN Shigeyuki Suzuki 10.18926/ESR/13844 With regards to the origin and evolution of the Pleistocene tracts (Lalmai, Madhupur and Barind tracts) of Bangladesh, two trends of thoughts are common. Most of the authors believed that the Madhupur, Barind and Lalmai tracts represent tectonically uplifted surface. Some researchers have different opinion and they believed that the Lalmai hills and the Madhupur locality represent tectonically uplifted blocks but the whole Barind tract and the major portion of the Madhuput tracts are not tectonically uplifted, rather these are originated by erossional-depositional processes. In order to solve the problems associated with origin and evolution of Pleistocene tracts of Bangladesh, further study is needed. Borehole data may be collected and fusion images can be prepared from aerial photographs and setellite images to detect netectonic imprins and geomorphological signatures of the areas. Elaborate laboratory analysis of sediment deposits, radiocarbon dating my indicate a new dimension about the origin and evolution of these tracts. No potential conflict of interest relevant to this article was reported.