テフラの鉱物特性から見た山陰の砂丘

Along the Japan sea coast of western part of Izumo plain in Shimane prefecture and the Japan sea coast from central to eastern part in Tottori prefecture, coastal sand dunes are well developed.
In these districts, Quatemary pyroclstics and volcanic ashes ejected from many volcanoes such as Daisen (DMP, DKP, KmA, HgA), Sambe (SKP, SUn), Aso (Aso-4), Aira (AT) and Kikai (Ah), are interbeded with eolian sand deposits. They are exactly distinguished by chemical characteristics of their magnetite, and volcanic glass due to chemical analyses by EPMA.
The relationship of eolian sand deposits to these tephra deposits are shown in Fig.3 and 12.
The eolian sand deposits are found in three horizons, one conformably overlying the Middle terrace deposits in Riss-Wurm stage (Ancient eolian sand dune I), one superposed on the Daisen Matsue fall pumice (DMP) with conformable relation and covered by loamy sediment correlated to Aso-4 tephra (ancient eolian sand dune II), other overlying the Akahoya ash (Ah) (Recent eolian sand dune).
The ancient eolian sand dune II has developed continuously to the ancient eolian sand dume I in the circumstances of the lowering in the sea level with eustatic sea level changes in Riss-Wurm stage.
Recent eolian sand dune was developed under strong wind condition in the circumstances of the lowering in the sea level after deposition of Akahoya ash (Ah).