Quaternary strata distributed in the Sasagami Hills are stratigraphically divided into the Yamadera, Sasagami, Aganogawa, Anchi and Nihonmatsu Formations in ascending order. Moreover, debris (Gozu Debris flows) which flowed down from the Gozu mountains are subdivided into seven beds and interfinger with the three latter formations. The Aganogawa, Anchi and Nihonmatsu Formations are terrace deposits which are composed of gravel, sand and silt beds. The complete sequence of the Yamadera Formation comprises sand and gravel beds (the lower member), silt or silty sand beds (the middle member) and sand beds (the upper member). The total thickness is about 80 meters. This Formation unconformably covers the Pliocene Dainichi Formation with a basal gravel bed. This unconformity is named the Yamadera Unconformity. The Sasagami Formation is composed of irregular alternation of gravel, sand and silt beds (the lower member), regular alternation of sand and silt beds (the middle member) and alternation of gravel, sand and silt beds (the upper member). The total thickness exceeds 70 meters and unconformably covers the Yamadera Formation. This unconformity is named the Sasagami Unconformity. Gozu Debris flow deposits widely cover the Yamadera and Sasagami Formations with unconformity (Gozu Unconformity). The Yamadera and Sasagami Formations are correlated with the Pliocene-Lower Pleistocene Uonuma Group in Cenozoic Niigata sedimentary basin. The Aganogawa, Anchi and Nihonmatsu Formations are correlated with deposits of "high", "middle" and lower terraces in Japan, respectivly. The Yamadera and Sasagami Unconformities are closely connected with the birth and growth of the sedimentary basin of the Uonuma Group. Distribution of these unconformities are limited to the marginal area of the basin. The present-day topography of this area is principally controlled by upheaval movement of the Gozu massif at the stage during the Gozu Unconformity was formed.