岡山大学理学部地球科学教室Acta Medica Okayama1340-74141912012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―2537ENHirokazuYukawaKazuoTeradaGeSunShigeyukiSuzuki10.18926/ESR/49211Erect 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 Okayama1340-74142512018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15ENShigeyukiSuzukiGraduate School of Natural Science and Technology, Okayama UniversityYoichiAzuma平寺町松岡兼定島 4-1-1 **YasuyoDeyama平寺町松岡兼定島 4-1-1 **HirokazuYukawaFukui Prefectural Dinosaur MuseumMayumiUsuiFujigakuin-Okayama10.18926/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.