Fluvioglacial Sediments and Eniwa-a Tephra in the Nanatsu-numa Cirque Area, Northern Hidaka Range, Hokkaido, Japan
日高山脈北部七ッ沼カールの融氷河流堆積物と恵庭a火山灰

Takanobu SAWAGAKI, Naoko MATSUOKA, Shogo IWASAKI, Kazuomi HIRAKAWA
2012 Journal of Geography (Chigaku Zasshi)  
One of the key sites of late Quaternary glaciations in the Hidaka Range is the Nanatsu-numa cirque area where glacial landforms and sediments can be correlated with the key marker tephra, En-a (17-18ka) , which allow glacier extent and fluctuations around the LGM to be examined precisely. This site has been identified as a type locality for defining two stadials, Poroshiri Stadial (older) and Tottabetsu Stadial (younger) , during the last glaciation in this area. We made a detailed description
more » ... tailed description of the stratified sediments interpreted as glaciofluvial deposits, located immediately below the Nanatsu-numa cirque. We discovered that: (a) these deposits formed the proximal part of glacier terminus; (b) En-a is included in all layers of sediment to a depth of 15 m; and (c) several boulder layers show cyclical debris flow sedimentation facies, which were probably due to En-a covering the glacier surface causing a sudden ice melt. Consequently, all stratified sediments at this site were deposited during the younger stadial of the last glaciation in the vicinity of the glacial terminus.
doi:10.5026/jgeography.121.252 fatcat:l6yungs2gfdtlaivscgd3zw34a