Studies on the structure and formation of the oldest fossil ice body in Japan

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This research was two years project to study the fossil ice body of Kuranosuke Snow Patch in Japanese Northern Alps. In 1988, inner structure of the ice body was observed in vertical holes which penetrate to the bottom of the ice body with a depth of 19m. And many pieces of plants for ^<14>C dating, ice samples for physical and chemical analyses and basal sediment for analysis of dynamical process were collected from the hole.The age of this ice body was found to be 1700 - 1800 BP at the basal part, around 1000 BP at a height of 13m from the bottom and after 1960 above that. Distinct differences were found in the physical and chemical character of ice between the upper part and the lower part of the unconformable layer at a height of 13.2m from the bottom.Peri-glacial sediment studies and the samples analyses revealed that this area was warm and covered with alpine plants about 6000- 7000 BP,and after about 2000 BP, the ice body was formed under the climate colder than the present. After the formation of the ice body, much accumulation due to orographic effect protect the ice body from the surface melting, and also, the bottom melting was small due to cold ground temperature.Many evidences of ice flow were found, though the flow speed was small because the terminal moraine dammed up the ice movement. Therefore, this ice body was considered to be a glacier in the past. However, clear evidence of the present flow could not be found.