Geomorphology of the Byobusan Sand Dune Area, Aomori Prefecture

Abstract

The results of the author's study on the Byobusan sand dune area along the Japan Sea to the west of Tsugaru plain are as follows ;(1) According to grain-size analysis the sand in this area is classified into four groups ; recent dune sand (A type : Mdφ= 1.51-1.76Q, dφ=0.26-0.33), older dune sand (B type : Mdφ=0.68, Qdφ=0.48), sand derived from the Byobusan formation underyling the sand dunes (C type : Mdφ=1.48, Qdφ=0.66), and beach sand (D type : Mdφ=1.12, Qdφ=0.64) (Fig. 2, Table 1). The Byobusan formation is correlated to the Shimosue-yoshi stage.(2) Three levels of terraces are recognized in this area; 10 m terrace, 20 m terrace and 30-40m terrace, the figures indicate their heights above the sea-level (Fig. 5). These three levels have been formed by eustatic sea level change since the Shimosueyoshi stage (Riss-Wurm interglacial stage).(3) The pattern of the sand dunes is characterized mainly by longitudinal dunes and parabolic or U-shaped dunes (Fig. 7·8). The recent sand dunes cover the older sand dunes and volcanic ash layer on them.