北海道海岸平野における完新世堆積環境の変遷 : 1.クッチャロ湖堆積物の珪藻遺骸群集

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Diatom assemblages of the sediments from two sites near Kutcharo Lake were analyzed to clarify the change in sedimentary environments caused by Holocene sea level fluctuation. Based on the ecological spectrum of the diatoms, the sedimentary history near Kutcharo Lake is inferred to have been as follows : (1) There were lowland peat bogs along the Okhotsk Sea coast. (2) The sediments of the lowermost Tr-1 zone were deposited on the littoral bottom of the paleo-Kutcharo Bay, which had been formed prior to 9,000 y.B.P. by the Holocene transgression. (3) Sedimentation in the MD-a subzone took place on the bottom of the neritic regions and in the MD-b subzone, and also on the bottom of the shore regions of the paleo-Kutcharo Bay. (4) The shore regions of the paleo-Kutcharo Bay changed directly into freshwater bogs during a regression from 6,000 to 5,000 y.B.P. (6) About 4,000 y.B.P., some ponds or small lakes developed in the bogs which had been formed at about 5,000 y.B.P. at two sites near Kutcharo Lake.
1984-12-30