北アルプス南東部, 梓川一ノ俣谷の氷河地形と氷河の消長 Glacial Geomorphology in the Ichinomata-dani Valley, Northern Japanese Alps
これまで氷河地形研究がほとんどおこなわれてこなかった北アルプス南東部, 梓川支流の一ノ俣谷流域で, 圏谷・U字谷・堆石などの氷河地形の分布を記載し, 氷河の消長史を明らかにした。開析・変形の程度の異なる氷食地形と堆石の分布およびそれぞれの位置関係から, 一ノ俣谷の氷河前進期は, 古い方から順に, 中山乗越期・横通沢期・東天井期の3期に区分される。各時期の氷河末端高度は, 中山乗越期; 2,120m, 横通沢期; 2,260m, 東天井期; 2,600mである。氷河地形の開析の程度から, 中山乗越期は最終氷期前半の亜氷期に, 横通沢期は後半の亜氷期の初期 (25ka) に, 東天井期は最終氷期極相期にそれぞれ対比される。
This paper clarified that glacial geomorphology and late Pleistocene glacial fluctuations in the Ichinomata-dani Valley, Azusa-gawa River, southeastern part of the northern Japanese Alps. In this valley, there was no previous study about glacial geomorphology and geology.<br>Based on the distribution of the glacial landforms and deposits, such as cirques, U-shaped valleys, and terminal, lateral and ground moraines, and the differences in dissection of glacial landforms, three glacial stages : the Nakayama-nokkoshi stage, Yokodoshi-sawa stage, and Higashitenjo stage, in order from oldest to youngest, are recognized in the study area. The glacial terminus in each stage was located at 2, 120m, 2, 260m and 2, 600m in altitude, from older to younger. Glacial landforms of Yokodoshi-sawa and Higashitenjo stages consist of fresh cirques and glaciated valley, which had been slightly modified by periglaciation, but those of Nakayama-nokkoshi stage are composed of dissected trough. These show that glacial retreat stage for a long time and/or non glacial stage existed between Nakayama-nokkoshi and Yokodoshi-sawa stages.<br>According to the tentative correlation of glacial stages in the southern part of the northern Japanese Alps, glacial stages in the Ichinomata-dani Valley are correlated as follows: 1) Nakayama-nokkoshi stage, the early stage of the Last Glacial period (before 60ka); 2) Yokodoshi-sawa stage, the first glacial advance in the late stage of the Last Glacial period (about 25ka); 3) Higashitenjo stage, the Last Glacial maximum (about 20ka). In the Late Glacial, there was no glacier in the Ichinomata-dani Valley.
- 季刊地理学 = Quarterly journal of geography
季刊地理学 = Quarterly journal of geography 51(2), 114-124, 1999-06-15
The Tohoku Geographical Association