湖山池の地質環境と地史的変遷  [in Japanese] Geoenvironment and Geologic history of Lake Koyamaike, Tottori Prefecture  [in Japanese]

海跡湖である湖山池の地学的な環境と, 形成過程について述べた。湖山池は更新統の湯山砂層によって鳥取湾入部から分断されて成立した。更新統以降の湖山池が海岸砂丘の消長と関連して現状にいたった経過を湖底地形, 試錘資料, 人類遺跡の分布などから検討し, 完新世以降の湖山池の変遷についてを論じた。6000-5000-年前の縄文海進期には2m程度の湖面上昇, 2500-1800年前の弥生期には湖面低下があった。試錘資料などから湖山池は北から直接に日本海に流出していたものと思考される。

Lake Koyamaike is a coastal lake facing the Japan Sea on the north, in San'in district. The lake was formed by a sand dune and sand bar (the Old Sand-dune and Yuyama formation) after the Middle Pleistocene to Holocene. The results of drill-core analyses and previous studies of coastal topography have revealed the geologic history of the lake Koyamaike as follows: (1) Two marine enbayments recognized in the Pleistocene Tottori Bay. They were separated by the deposition of sand-dunes and sand bar (the Koyama Sand-dune and sand bar from Tenjinyama to Fuse) (2) Before 6000-5000 yrs. marines and and silt beds were deposited in the Holocene Tottori Bay area. The sea level rises not less than +2m. (3) Before 2500-1800 yrs. the sea level was lower than the present. (4) Detailed underground analyses have revealed that the outlet of Lake Koyamaike may have been directed to the north.