Geohistoric development of Debris flow at the western foot of Gozu Mts. to the east of Niigata Plain, Japan

Debris flow composes the important part of mass movement and is called dosekiryu in Japan. Debris flow deposits, from the middle Pleistocene to the Recent, are widely distributed at the western foot of the Gozu mountains. It is divided into the following seven gravel beds in ascending order； the Gozu gravel bed and the Nakayama gravel bed (the middle Pleistocene), the Dainichigahara gravel bed (the last interglacial stage), the Imaita gravel bed (the early Wurm glacial stage), the Murasugi gravel bed (the end of the Wurm glacial stage), the Tsubeta gravel bed (the Johmon age of the Holocene) and the 1967 gravel bed (Aug.28, 1967). The Gozu Debris fow did not occur at the maximum Wurm stage, and main part of the Gozu debris flow occurred at the middle Pleistocene, that is, at the extreme upheaval stage in the Island Arc Disturbance. Investigation of the geohistoric development of the late Quaternary Gozu debris flow leads to the conclusion that the most important cause of occurrence of the Gozu debris flow is not the paleoclimatic effect but is the growth of the Gozu mountains