首页 | 本学科首页   官方微博 | 高级检索  
     


Progressive formation of modern drumlins at Múlajökull,Iceland: stratigraphical and morphological evidence
Authors:Ívar Örn Benediktsson  Sverrir A. Jónsson  Anders Schomacker  Mark D. Johnson  Ólafur Ingólfsson  Lucas Zoet  Neal R. Iverson  Johann Stötter
Affiliation:1. Institute of Earth Sciences, University of Iceland, Reykjavík, Iceland;2. Department of Geology, UiT The Arctic University of Norway, Troms?, Norway;3. Department of Earth Sciences, University of Gothenburg, G?teborg, Sweden;4. The University Centre in Svalbard (UNIS), Longyearbyen, Norway;5. Department of Geoscience, University of Wisconsin‐Madison, Madison, WI, USA;6. Department of Geological and Atmospheric Sciences, Iowa State University, Ames, IA, USA;7. Institute of Geography, University of Innsbruck, Innsbruck, Austria
Abstract:The drumlin field at Múlajökull, Iceland, is considered to be an active field in that partly and fully ice‐covered drumlins are being shaped by the current glacier regime. We test the hypothesis that the drumlins form by a combination of erosion and deposition during successive surge cycles. We mapped and measured 143 drumlins and studied their stratigraphy in four exposures. All exposures reveal several till units where the youngest till commonly truncates older tills on the drumlin flanks and proximal slope. Drumlins inside a 1992 moraine are relatively long and narrow whereas drumlins outside the moraine are wider and shorter. A conceptual model suggests that radial crevasses create spatial heterogeneity in normal stress on the bed so that deposition is favoured beneath crevasses and erosion in adjacent areas. Consequently, the crevasse pattern of the glacier controls the location of proto‐drumlins. A feedback mechanism leads to continued crevassing and increased sedimentation at the location of the proto‐drumlins. The drumlin relief and elongation ratio increases as the glacier erodes the sides and drapes a new till over the landform through successive surges. Our observations of this only known active drumlin field may have implications for the formation and morphological evolution of Pleistocene drumlin fields with similar composition, and our model may be tested on modern drumlins that may become exposed upon future ice retreat.
Keywords:
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号