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Sökning: WFRF:(Jonsson Anders) > Konferensbidrag > BENEDIKTSSON Ívar Örn

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1.
  • Jonsson, Sverrir, et al. (författare)
  • THE MÚLAJÖKULL DRUMLIN FIELD - SEDIMENTOLOGY AND GEOMORPHOLOGY
  • 2011
  • Ingår i: Geological Society of America abstracts with programs Minneapolis 2011.
  • Konferensbidrag (refereegranskat)abstract
    • The drumlin field in front of Múlajökull, a surge-style, outlet glacier from Hofsjökull in Iceland, is the only known active drumlin field (Johnson et al., 2010). The aim of this study is to further explore the formation of drumlins in a modern glacial environment. We use data from geological sections, DEMs, aerial imagery and field mapping. Here we present preliminary results from section logging and geomorphological mapping in the summer of 2011. Geomorphological mapping of the drumlin field both with DEMs and ground proofing has revealed over 100 drumlins and a number of drumlinized ridges. The drumlins furthest from the present ice margin appear broader and have lower relief than those closer to the ice. We suggest that this reflects an evolution of the drumlin form during recurrent surging. The drumlins farther away from the ice have experienced fewer surges than those that have just been uncovered due to retreat of the ice margin. During successive surges, the drumlins become narrower and develop higher relief. In one section close to the present ice margin, we identified at least 9 till beds in the crest of a drumlin, each likely the product of a surge, representing approximately 1/3 of the drumlin relief. The top till bed parallels the drumlin form and truncates the older tills. The older units also dip parallel to the drumlin form, but at a slightly lower angle. We believe that this represents an earlier, broader shape of the drumlin prior to the more recent surges, implying an evolution of form similar to that seen in the evolution in form in the drumlin field. The Múlajökull drumlins have thus grown during surging by erosion on the proximal end and sides of the drumlin followed by accretion of till sheets concentrically on the resulting form.
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2.
  • Schomacker, Anders, et al. (författare)
  • THE ACTIVE DRUMLIN FIELD AT THE MÚLAJÖKULL SURGE-TYPE GLACIER, ICELAND – GEOMORPHOLOGY AND SEDIMENTOLOGY
  • 2011
  • Ingår i: Geological Society of America abstracts with programs Minnespolis 2011.
  • Konferensbidrag (refereegranskat)abstract
    • Recent marginal retreat of Múlajökull, a surge-type, outlet glacier of the Hofsjökull ice cap, central Iceland, has revealed a drumlin field consisting of over 50 drumlins. The drumlins are 90–320 m long, 30–105 m wide, 5–10 m in relief, and composed of multiple beds of till deposited by lodgement and bed deformation. The youngest till layer truncates the older units with an erosion surface that parallels the drumlin form. Thus, the drumlins are built up and formed by a combination of subglacial depositional and erosional processes. Field evidence suggests each till bed to be associated with individual, recent surges. We consider the drumlin field to be active in the sense that the drumlins are shaped by the current glacial regime. To our knowledge, the Múlajökull field is the only known active drumlin field and is, therefore, a unique analogue to Pleistocene drumlin fields.
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