Abstract
The chronological formation of glacial landforms and accumulation terracing were examined in the Yabusawa Valley on the north slope of Mt. Senjogatake, Southern Japanese Alps. Glacial land-forms such as glacial troughs, truncated spurs, lateral and terminal moraines, and roches mouton-nees represent three distinct glacial advances and/or standstill called Yabusawa I, Yabusawa II, and Yabusawa III. Yabusawa I is the oldest and Yabusawa III is the youngest. During the Yabu-sawa I substage we determined that the glacier advanced down to an altitude of 2, 250m above sea level based on the glacial trough and its associated trimline. During the Yabusawa II substage the glacier advanced down to an altitude of 2, 550m above sea level as indicated by lateral and terminal moraines (Mu moraine). The bottom of the Yabusawa I glacial trough was shaped by meltwater into a narrow V-shaped valley during the retreat of the Yabusawa I glacier and the advance of the Yabusawa II glacier. During the Yabusawa III substage the glacier remained within the cirque to form a typical terminal moraine (Ms moraine) at 2, 900 m above sea level. Con-sidering the geomorphological development of glacial landforms and the glaciation of the Central Japanese Alps, situated ca. 50 km west of Mt. Senjogatake, the Yabusawa I substage probably repre-sents the early stadial of the Last Glaciation. Both the Yabusawa II and III substages seem to indicate the late stadial of the Last Glaciation. The accumulation of thick gravels within a very muddy matrix, the Yabusawa terrace gravel, occurred rapidly about 9, 000 years BP and was pro-bably associated with slope failure in the surrounding mountains, not with glaciation. This failure was possibly influenced by the melting of mountain permafrost that probably remained in this area during the early Holocene.
