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. erect fossil stump fossil forest Nariwa Group Upper Triassic Xenoxylon
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. Beachrock Akagurisaki non-calcareous cement ionization tendency