京都府京丹後市の更新統の堆積環境の推定および日本海側更新統からの珪藻種Pseudopodosira kosugiiの初産出

摘要

We conducted diatom analysis, pollen analysis, and radiocarbon dating of a black mud layer with an altitude of about 5 m located in the coastal area of Kyotango City, Kyoto Prefecture, Japan. Radiocarbon age of the tree fossil in this layer was older than 43,500 yBP. Pollen analysis reconstructed cool-temperate deciduous broad-leaved forests accompanied with Cryptomeria japonica and Pinus, but some pollen grains of evergreen Quercus subgenus Cyclobalanopsis were also detected. The fossil diatom assemblage, mainly composed of brackish species with the dominance of Pseudopodosira kosugii, suggests that the layer was deposited on a salt marsh around the high tide level of a river mouth mudflat This is the first report of P. kosugii from the Pleistocene series of the Japan Sea Coast%京都府京丹後市久美浜町蒲井の標高約5mに位置する更新統黒色泥層の珪藻分析，花粉分析， 放射性炭素年代測定を行った.堆積年代は43,500yBPよりも古いと推定された.花粉組成からは，スギを伴う冷温帯落葉広葉樹林にマツ属が沿岸部に生育する植生が想定されたが，照葉樹であるァカガシ亜属の花粉も検出された.珪藻化石群集の優占種はPseudopodosira kosugiiであり, 本州日本海側の更新統からの本種の初報告である.本種と随伴種から，黒色泥層の堆積環境は汽水泥質干潟の高潮線付近だったと推定された.