Late Quaternary Glaciation in the Esaoman-Tottabetsu Valley, Hidaka Range, Hokkaido, Japan

Abstract

Late Quaternary glacial fluctuations in the Esaoman-Tottabetsu Valley, inthe northern Hidaka Range, central Hokkaido were reconstructed based on stratigraphy of glacial landforms and sediments. By mean of tephrochronology, the two previously known stadials of the Last Glacial Stage, the Poroshiri and Tottabetsu Stadials, were reassessed. Shikotsu 1 tephra overlain by the terminal moraine of the Poroshiri Stadial at the river bed of 850m a. s. l. indicates that the glacier reached its maximum at around 40ka (Oxygen Isotopic Stage 3: OIS-3). This advance should have been initiated in the preceding cold period of 01S-4. Kuttara 6 tephra (86 ka) in the proglacial outwash deposits indicates that a glacier fluctuated in the vicinity of the cirque bottom even in the relatively warm period of the early Last Glacial Stage (01S-5b). Contrary to this stadial, the glacial and proglacial deposits including Eniwa a tephra (18 ka) show that the glacial advance during the Tottabetsu Stadial (LGM) in this region was restricted within the cirque bottom. The penultimate glaciation, named the Esaoman Glaciation in this study, was suggested by the discontinuously traceable remnant bed topography along the river basin. These features recommend that the glacial advance of this stage reached at 750m a. s. l., lower than during the Last Glacial Stage.