Research on the Relationship between the Formation of Sand Dunes and Intercalated Humic Layers

Abstract

This paper consists of a historical review on the formation of sand dunes and some considerations on the relationship between the dune formation and the intercalated humus layers in several districts. The following results were obtained;(1) Buried dunes beneath the surface of Tatebayashi upland in Tochigi Prefecture.Sand layers constituting the buried dunes are divided in two, both having been deposited under stable circumstances. And volcanic ash layers are found in this district, divided into three; upper, middle and lower. There is every reason to believe that these dunes were formed at the beginning of the fall of the middle ash, or at the end of that of the lower ash.(2) Sand dunes on Sanrihama and Kaetsu uplands.The formation of some of Sanrihama dunes were due to a relative rising of sea level in early Holocene epoch. At the bottom of shallow valleys in Kaetsu upland, humus accumulation occured in stagnant water prior to the formation of dunes.(3) Kashima dunes in Ibaragi Prefecture.In the Kashima peninsula are found sand dunes with three intercalated humus layers, which are thought to have been formed after the formation of sand bars caused by a rise of sea level during the Jomon culture period, early Holocene.(4) Genkai dunes in Fukuoka Prefecture.Sand dunes of this area were formed during the time of high sea level in Pleistocene epoch. Aeolian sand layers are thin in depth and cover uplifted sand bars of marine deposits forming coastal terrace topography. Furthermore, five buried humus layers called Kurosuna are found among sand beds of Holocene dunes, which indicate the ages of dune formation and the stable period.