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

本研究是对日本北阿尔卑斯黑野介雪原的化石冰体进行为期两年的研究。1988年，观测到冰体内部结构的垂直孔洞，这些孔洞深入冰体底部，深度为19m。从洞中收集了许多用于^<14>C测年的植物碎片、用于物理和化学分析的冰样和用于动力过程分析的基底沉积物。该冰体的年龄在基底1700 ~ 1800 BP之间，在离底13m处约1000 BP，在13m以上为1960年以后。在距离底部13.2m高度处，不整合层的上部和下部冰的物理化学性质存在明显差异。冰期沉积物研究和样品分析表明，该地区约6000 ~ 7000 BP为温暖的高山植物覆盖区，约2000 BP后，在比现在更冷的气候条件下形成冰体。在冰体形成后，由于地形效应造成的大量堆积保护了冰体不受地表融化的影响，同时由于地温较低，底部融化较小。发现了许多冰流的证据，尽管由于末端冰碛阻塞了冰的运动，冰流的速度很小。因此，这个冰体在过去被认为是冰川。但是，没有找到目前流动的明确证据。

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.