Rock glacier development in the Northern Calcareous Alps at the Pleistocene-Holocene boundary

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• 作者：Andrew P. Moran^a ; ^{andrew.moran@uibk.ac.at" class="auth_mail" title="E-mail the corresponding author} ; Susan Ivy Ochs^b ; Christof Vockenhuber^b ; Hanns Kerschner^a
• 关键词：Rock glaciers ; Palaeoclimate ; 36Cl ; Alps
• 刊名：Geomorphology
• 出版年：2016
• 出版时间：15 November 2016
• 年：2016
• 卷：273
• 期：Complete
• 页码：178-188
• 全文大小：3313 K

文摘

Relict rock glaciers provide information on past discontinuous permafrost and former mean annual air temperatures. A lack of records showing former permafrost distribution along the northern Alpine fringe prompted the investigation and numerical dating of a belt of relict rock glaciers in the Karwendel Mountains of the Northern Calcareous Austrian Alps. In two neighbouring cirques that were still glaciated during the early Younger Dryas, eleven ³⁶Cl exposure ages from boulder surfaces were obtained. The ages imply the onset of rock glacier activity around ~ 12.3 ka with subsequent stabilization and permafrost melt out no later than ~ 10.1 ka. Hence, rock glacier formation coincided with glacier retreat in the cirques around the mid-Younger Dryas and continued into the early Holocene. As permafrost induced features, the rock glacier termini indicate the local past lower limit of discontinuous permafrost in open cirque floors at ~ 2000 m asl, which is around 400 m lower than during the mid-twentieth century at comparable locations in the Karwendel Mountains. Thus, a mean annual air temperature reduction of ~− 2.6 to − 3.8 °C relative to the mid-twentieth century is inferred. Based on a minimum glacier equilibrium line altitude in the cirques, a summer temperature reduction of less than − 2.6 to − 1.8 °C is shown, suggesting an increased seasonality at the time of rock glacier activity.