抄録
The Late Quaternary deposits of the Niigata lowland, recently drilled by authors, can be divided into four formations in ascending order: pre-gravel bed (G1) 1, gravel bed 1, the Nishikanbara Group and the Shirone Group, respectively. Of these, according to age determination by the Radio-Carbon method, the age of the gravel bed 1 is now estimated to be between 31, 000 and 26, 000 y. B. P.
The Nishikanbara Group may have been deposited between 26, 000 to 25, 000 y. B. P., while the Shirone Group ranges in age from 20, 000 y. B. P, to the present.
Possibly gravel bed 1 is a buried terrace deposit, produced during a glacial age when sea level was much lower than at present. It is perhaps correlatable to Hauptwürm 1.
The Nishikanbara Group is thought to have been deposited during the inter-ice age that followed the preceeding stage of sea-level lowering, while the Shirone Group was deposited during a later stage when sea level again became higher following the Maximum Würm, begining about 20, 000 to 18, 000 years ago.
