The Holocene Successive Change of Diatom Assemblages of Drilling Core Samples in Lake Tega, Kanto Plain, Japan

Abstract

The drilling surveys of lake deposits were done at the two sites in Lake Tega in order to clarify the environmental changes of the lake during the Late Holocene. Five zones of diatom assemblages are recognized in the Holocene lake deposits. The following changes of lake environments are presumed by the successive change of diatom assemblages.
Lake Tega had been a brackish lagoon before the salinity of lake water became variable in 1700-1850y. AD. This salinity change was caused presumably by the artificial change of the course of the River Tone. The fresh water environment has continued since about 1850y. AD.