Diatom thanatocoenoses from bore hole core samples of lagoon Hachiro-gata reclaimed land and deduced paleoenviroment in Akita Prefecture, northeast Japan.

Abstract

The diatom thanatocoenoses from the bore-hole samples of the lagoon Hachiro-gata r ecl-aimed land were analysed in this paper. The resulsts are as follows.
(1) Identified taxa were estimated with 106 species,17 varieties and 2 formae of 36 genera.
(2) The marine species are dominant in the samples below 41-33m depth. Especially the planktonic species are calculated more than 50 % in this horizon. Also, the brackish water species increases gradually in the middlep art.
(3) The fresh water species are dominant at the uppermost deposit.
(4) The sedimentary environments at the bore-hole site are presumed to be changed from the seawater area to freshwater area through brackish water one toward the uppermost horizon.