Holocene diatom assemblages in Takagami lowland, central part of Choshi Peninsula, and its relation to changes of sea-level.

Abstract

The Holocene deposits in Takagami Lowland can be divided into 5 zones of diatom assemblages. About 8000-10 000 y BP, marine transgression started. Due to rapid transgression, the drowned valley extended until 6000 y BP. About 5500-6000 y BP, a beach ridge cut off this drowned valley. About 5000 y BP, in the middle and eastern part of Takagami lowland fresh-water marsh was formed; in the NW part, marine sand with shell fragments and diatom valves of marine species were deposited frequently on the freshwater marsh by storm surges till about 3000 y BP. -after English summary