地学雑誌
Online ISSN : 1884-0884
Print ISSN : 0022-135X
ISSN-L : 0022-135X
論説
氷河地形調査と表面露出年代測定に基づく東南極宗谷海岸南部Skarvsnesにおける氷床後退過程の復元
川又 基人菅沼 悠介土井 浩一郎澤柿 教伸服部 晃久
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2020 年 129 巻 3 号 p. 315-336

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 The purpose of geomorphological studies in East Antarctica is to understand past fluctuations of the Antarctic Ice Sheet, which is essential to constrain ice sheet models and predict future behavior of the East Antarctic Ice Sheet. Here we show a deglacial history of Skarvsnes, at the southern part of the Soya Coast, East Antarctica based on a geomorphological field survey and newly obtained surface exposure ages. Bedrock higher than ca. 250 m a.s.l. at the northwest part of Skarvsnes (Skjegget) is weathered extensively, whereas bedrock below ca. 250 m a.s.l. is relatively unweathered. The degree of weathering of bedrock above 250 m a.s.l. is similar to that at the northern part of the Soya Coast, which is thought to have been ice-free throughout the last glacial period. Therefore, a clear difference in the degree of weathering depending on altitude probably indicates the lower limit of the ice sheet elevation during the last glacial period at Skarvsnes. Judging from the multiple directions of glacial striae, the ice sheet covering the area retreated while changing flow direction under the influence of the bedrock topography after the last glacial period. Since ca. 9 ka, the ice sheet is thought to have thinned and eventually divided into two major ice streams (northward and southward) that were obstructed by a 362 m a.s.l. mountain (Shirasuso-Yama), at the southeastern part of Skarvsnes. However, the timing of the initiation of the ice sheet retreat and its duration remain unclear. Therefore, additional surface exposure ages from various areas and heights at Skarvsnes are required for a detailed reconstruction of the ice retreat history and to understand its mechanism.

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© 2020 公益社団法人 東京地学協会
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