Architecture and structural evolution of an early Little Ice Age terminal moraine at the surge-type glacier Múlajökull, Iceland

Benediktsson, Í. Ö., Schomacker, A., Johnson, M. D., Geiger, A. J. , Ingólfsson, Ó. and Guðmunsdóttir, E. R. (2015) Architecture and structural evolution of an early Little Ice Age terminal moraine at the surge-type glacier Múlajökull, Iceland. Journal of Geophysical Research: Earth Surface, 120(9), pp. 1895-1910. (doi: 10.1002/2015JF003514)

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Abstract

The internal architecture and structural evolution of the Arnarfellsmúlar terminal moraine at Múlajökull, a surge-type glacier in central Iceland, is described in order to demonstrate submarginal and proglacial glaciotectonic processes during glacier surging, as well as constraining the age of the maximum extent of the glacier. The moraine is 4–7 m high, 50–100 m wide, and composed of a highly deformed sequence of loess, peat, and tephra that is draped by till up to the crest. The internal architecture is dominated by steep, high-amplitude overturned folds and thrusts in the crest zone but open, low-amplitude folds on the distal slope. Section balancing suggests a basal detachment (décollement) depth of 1.4 m and a total horizontal shortening of around 59%. This implies that the glacier coupled to the foreland about 70 m up glacier from its terminal position to initiate the formation of the moraine. The structural evolution is polyphase in that the formation commenced with low-amplitude open folding of the foreland, followed by overfolding and piggyback thrusting. Radiocarbon dating and analysis of tephra layers, along with historical references, indicate that the most likely time of moraine formation was between A.D. 1717 and 1760, which suggests that Múlajökull had its Little Ice Age maximum and most extensive surge earlier than many other surge-type glaciers in Iceland.

Item Type:Articles
Additional Information:Funding from the Carlsberg Foundation, the University of Iceland Research Fund, the Energy Research Fund of Landsvirkjun, and the Icelandic Center for Research (RANNÍS) is gratefully acknowledged.
Keywords:glaciers, surging, sedimentology, glaciotectonics, geomorphology, Iceland
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Geiger, Dr Alessa
Authors: Benediktsson, Í. Ö., Schomacker, A., Johnson, M. D., Geiger, A. J., Ingólfsson, Ó., and Guðmunsdóttir, E. R.
Subjects:G Geography. Anthropology. Recreation > GB Physical geography
Q Science > QE Geology
College/School:College of Science and Engineering > School of Geographical and Earth Sciences
Journal Name:Journal of Geophysical Research: Earth Surface
Journal Abbr.:JGR
Publisher:Wiley-Blackwell Publishing Ltd.
ISSN:2169-9003
ISSN (Online):2169-9011
Published Online:24 September 2015

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