The Last Glacial Age Accumulation Terracing around the Iide and the Asani Mountains, Northeastern Japan

Abstract

River terraces, including accumulation terrace, were investigated in the Iide and Asahi Mountains. This paper especially describes the terraces of the Last Glacial age on the basis of stratigraphical, geomorphological and pedological evidences as well as ¹⁴C age determination.
The results are summarized as follows.
1) In the studied river basins, such as the Miomote, the Arakawa, the Tamagawa, the Tainai and the Kajikawa Rivers, two accumulation stages in the Last Glacial age were detected. The accumulation and the following incision are considered to have been caused by the climatic changes.
2) The earlier and the later accumulation stages terminated at least before 35, 000yr B. P. and before 12, 000yr B. P., respectively.
3) The earlier accumulation terrace are widely distributed along the middle courses of rivers, although not in the upper valleys. The latter one are formed only in the upper valleys in the Mountains and at the outlets of gorges through high mountain area. These facts indicate that the earlier accumulation is more conspicuous than the later one.