Shogo Iwasaki

Late Quaternary glaciations in Japan

A general introduction to the Quaternary glaciations in the Japanese high mountains is presented. Particular attention is paid to the two most significantly-glaciated mountain ranges, and recent knowledge of the glacial history in the Japanese Alps and Hidaka Mountains is presented. Six glacial advances are recognised in the Japanese Alps that occurred during the penultimate glacial cycle, the Last Glaciation, and the Holocene. In the high Japanese mountains, the maximum advance during the Last Glaciation is commonly recognised during Marine Isotope Stage (MIS) 4 with subsequent advances occurring just before 24 ka BP, 18–20 ka PB, 11–10 ka BP and in the early Holocene. In the Hidaka Mountains, recent tephrochronological investigations have revealed the age and extent of the maximum glacier advance during MIS 5a, MIS 3, MIS 2 and MIS 6. Mountain glaciers in Japan were less extensive during the Last Glacial Maximum. This is out of phase with the continental ice sheets in the northern hemisphere.

Evidence of past migration of the ice divide between the Shirase and Sôya drainage basins derived from chemical characteristics of the marginal ice in the Sôya drainage basin, East Antarctica

Ice originating near the inland ice divide of the ice sheet can reappear as marginal ice at the surface near the ice terminal in the ablation area. We have analyzed d 18 O values and ion concentrations of the Skallen, Skarvsnes and Hamna terminal ice sections, located along the estuary line in the Soya drainage basin, East Antarctica. The data suggest that the upper part of the Skallen terminal ice section could have originated from inland precipitation on the Shirase drainage basin during marine isotope stage (MIS) 5e, while the upper part of Skarvsnes and Hamna terminal ice sections could have originated from inland precipitation on the Soya drainage basin. We calculate past elevation maps for the Antarctic ice sheet using the three-dimensional model, SICOPOLIS. This model suggests that the upstream portion of the Soya drainage basin during the glacial period (MIS 2, 3 or 4) was located to the northeast of its present location. A flow history is proposed wherein ice from the inland Shirase drainage area flowed over the present ice-divide line from the Shirase to the Soya drainage basin during the glacial period. The ice in the Soya drainage basin then flowed to the marginal part of the sheet after the ice divide had assumed its present position.