GLACIAL AND PERIGLACIAL ENVIRONMENTAL CHANGES IN LATE QUATERNARY IN THE DAISETSUZAN MOUNTAINS, CENTRAL HOKKAIDO

北海道中部大雪山晚第四纪冰川和冰缘环境变化

• 批准号: 12680091
• 负责人: NOBUYUKI Takahashi
• 金额: $ 1.98万
• 依托单位: HOKKAI-GAKUEN UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2002
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12680091/
• 关键词: the Daisetsuzan Mountains; the Ishikari River; paleo-lake Daisetsu (Ko-Daisetsuko); Quaternary; glacial stage; glacial and periglacial environment; glacial landform; glacial deposit (till); 高山帯; 周氷河環境; 最終氷期; 古環境; 永久凍土; 湖成堆積物; 軽石流堆積物; 氷縞粘土 /

It is the purpose of this research to clarify the glacial and periglacial environments in the late Quaternary in the Daisetsuzan Mountains where glacier landforms and paleoenvironment of last glacial stage have been hardly studied. Within the research period, it was able to clarify the distribution of some glaciers and the paleoenvironment of late glacial stage. First, in the Ishikarizawa River, the upper tributary of the Ishikari River, some kind of glacial sediments were found, and it was presumed that the glacier had expanded to near the altitude of 1050m in the first substage in the last glacial stage. Furthermore, near the altitude of 980m along the Ishikari River main stream, the older subglacial till with shearing structure was discovered. Next, a boulder (major axis of 4m or more) believed to be one of erratics on the flat-topped ridge (altitude of 1360m) near Ginsendai on the eastern side of the Daisetsuzan Mountains was discovered. The sediment considered to be a subglacial till is also distributed near the boulder, and it may be suggested that flat-topped ridges of the Daisetsuzan Mountains were widely covered with glaciers. Moreover, glacial landforms and sediments were recognized also around Mt Tomuraushi-yama of the southern Daisetsuzan Mountains, and the expansion areas of the glaciers in the first substage of the last glacial stage were presumed from relation with the history of Tomuraushi-yama volcano formation.On the other hand, Ishikari River dammed up by the volcanic activity about 30,000 years before in the last glacial stage, and consequently paleo-lake Daisetsu (Ko-Daisetsuko) was formed. Its expansion range became clear and radiocarbon dating of lacustrine sediments showed that the lake continued till the beginning of Holocene.In addition, in the alpine zone belonging to a discontinuous permafrost zone, the weather survey is continued and the periglacial environment has grasped quantitatively.

本研究的目的是弄清大雪山地区第四纪晚期的冰川环境和冰缘环境，该地区末次冰期的冰川地貌和古环境研究较少。在研究期间，可以明确一些冰川的分布和晚冰期的古环境。首先，在石狩川的上游支流石狩泽川发现了某种冰川沉积物，推测冰川在末次冰期的第一个亚阶段已经扩展到海拔1050米附近。此外，在石狩川干流沿着海拔980 m附近，还发现了具有剪切构造的古老冰下冰碛物。接着，在大雪山东侧的银仙台附近的平顶山脊（海拔1360米）上，发现了一个被认为是不规则岩石的巨石（长轴4米以上）。被认为是冰下冰碛物的沉积物也分布在巨石附近，这可能表明大雪山的平顶山脊广泛覆盖着冰川。此外，在大雪山南部的知村青山附近也发现了冰川地貌和沉积物，并根据知村青山火山形成的历史推测了末次冰期第一次冰期冰川的扩张区域。另一方面，在末次冰期约3万年前，石狩川因火山活动而堵塞，古大雪湖（Ko-Daisetsuko）由此形成。湖相沉积物的放射性碳年代测定表明，该湖一直延续到全新世初期，在属于不连续多年冻土带的高寒地带，继续进行气候调查，定量掌握了冰缘环境。