A Study of the Formation of Sand Dunes and Paleosols in the Würm Glacial Age, North Kyushu

Abstract

Examination of dune sand columns in the coastal region of North Kyushu, Japan, and the recognition of paleosols allowed the division of the dune sand formation into four members, which are Ashiya dune sand (the youngest, Holocene), Awaya dune sand, Enokizaka dune sand and Onizu dune sand (the oldest).
Some members of dune sand occur on each of two terrace surfaces. The upper surface occurs on the Ashiya beach deposits at approximately 8 metres above sea level and the lower surface occurs on the Mitoma beach deposits at about 1 metre above sea level. The upper surface is overlain four dune sand members with three layers of well developed paleosols; the lower surface is overlain three dune sand members with two layers of well developed paleosols. The upper surface predates the Würm Glacial and the lower surface correlates the WI/WII (Gettweiger) interstadial age.
Paleosols do not have a complete paleo-solum. The break between a paleosol and overlying dune sand of the succeeding deposits is associated with discontinuous gravel and peat. It would appear that the upper part of the solum of the paleosols had been stripped off prior to the deposition of the succeeding dune sand layer.
Peat at the base of the Awaya sand member immediately above the second paleosol gives a radiocarbon data (GaK-5157) of 22, 020±740 years B.P.
A hypothesis is presented suggesting that the dune sand members were accumulated by the prevailing wind of the directions ranging N to N10°W during substages of the Würm Glacial. The periods of soil development indicated by the paleosols were at interstadials in the Würm Glacial age.