Abstract
Ten rows of sand dunes ranging parallel to the present coastline are identified in the Echigo Plain, northern Japan. The timing of sand dune formation is determined by the dating of organic matter from the sand dune itself, peaty sediments of interdune lowlands, and basement sand dune sediments. When the sea level was highest, in the Jomon transgression, about 8,000 years ago, a barrier island system associated with lagoons was established along the innermost zone of the Echigo Plain. When the sea level was stable or a little lower then the peak sea level, about 6,000 years BP, the fluvial plain expanded quickly, due to high sediment supply from large rivers such as the Shinanogawa River.
Coastal dunes developed intermittently in response to halts in the advance of the coastline, resulting in the formation of the sand dune rows named Dunes I-1, I-2, I-3, I-4, II-1, II-2, II-3, II-4, III-1, and III-2. The formation ages of the sand dunes were confirmed in detail as follows : Dune I-1 in about 6,000 years BP, Dune I-2 in 6,000-5,500 years BP, Dune I-3 in 5,000 years BP, Dune I-4 in 4,500 years BP, Dune II-1 in 4,000 years BP, Dune II-2 in 3,500 years BP, Dune II-3 in 3,000 years BP, Dune II-4 in 2,000-1,700 years BP, Dune III-1 in 1,700-1,100 years BP and Dune III-2 in 1,100 years BP.
