TY - JOUR
T1 - The 1890 surge end moraine at Eyjabakkajökull, Iceland
T2 - a re-assessment of a classic glaciotectonic locality
AU - Benediktsson, Í Ö
AU - Schomacker, A.
AU - Lokrantz, H.
AU - Ingólfsson, Ó
N1 - Funding Information: The Eyjabakkajökull Project was funded by the University of Iceland Research Fund, Energy Research Fund of Landsvirkjun, Verkefna- og rannsóknarsjóður Fljótsdalshrepps (grants to ÍÖB and ÓI). Additional funding was provided to AS by the Royal Swedish Academy of Sciences and Christian og Ottilia Brorsons Rejselegat for yngre videnskabsmænd og -kvinder. ÍÖB acknowledges support from the Icelandic Research Fund for Graduate Students, the University of Iceland Research Fund and Landsvirkjun. Thanks are due to Mark Johnson, Jaap van der Meer, Torbjörn Andersson, Amanda Ferguson, Eygló Ólafsdóttir, Skafti Brynjólfsson, Susi Ebmeier, Antje Herbrich and Jón Björn Ólafsson for invaluable assistance, discussions and company during the 2006–2008 Eyjabakkajökull field campaigns. Rúnar Ingi Hjartarson and Björn Oddson are thanked for logistical assistance. Jaap van der Meer is specially thanked for fruitful discussions about the 1890 end moraine in the field and for constructive comments on an earlier version of this paper. Thanks are furthermore due to Kurt H. Kjær for providing the ground penetrating radar and for discussions and comments that improved the paper. Constructive comments by Roman Motyka and one anonymous reviewer are gratefully acknowledged.
PY - 2010/2
Y1 - 2010/2
N2 - The glaciotectonic architecture and sequential evolution of the Eyjabakkajökull 1890 surge end moraines in Iceland were studied for understanding better the formation and evolution of glaciotectonic end moraines and their relation to glacier dynamics. Based on morphological, geological and geophysical data from terrain cross-profiles, cross-sections and ground penetrating radar profiles, we demonstrate that three different qualitative and conceptual models are required to explain the genesis of the Eyjabakkajökull moraines. Firstly, a narrow, single-crested moraine ridge at the distal end of a marginal sediment wedge formed in response to decoupling of the subglacial sediment from the bedrock and associated downglacier sediment transport. Secondly, large lobate end moraine ridges with multiple, closely spaced, narrow asymmetric crests formed by proglacial piggy-back thrusting. Thirdly, a new model shows that moraine ridges with different morphologies may reflect different members of an end moraine continuum. This is true for the eastern and western parts of the Eyjabakkajökull moraines as they show similar morphological and structural styles which developed to different degrees. The former represents an intermediate member with décollement at 4-5 m depth and 27-33% shortening through multiple open anticlines that are reflected as moderately spaced symmetric crests on the surface. The latter represents an end member with décollement at about 27 m depth and 39% horizontal shortening through multiple high amplitude, overturned and overthrusted anticlines, appearing as broadly spaced symmetric crests. We propose that the opposite end member would be a moraine of multiple symmetric, wide open anticlinal crests of low amplitude. Our data suggest that the glacier coupled to the foreland to initiate the end moraine formation when it had surged to within 70-190 m of its terminal position. This indicates a time frame of 2-6 days for the formation of the end moraines.
AB - The glaciotectonic architecture and sequential evolution of the Eyjabakkajökull 1890 surge end moraines in Iceland were studied for understanding better the formation and evolution of glaciotectonic end moraines and their relation to glacier dynamics. Based on morphological, geological and geophysical data from terrain cross-profiles, cross-sections and ground penetrating radar profiles, we demonstrate that three different qualitative and conceptual models are required to explain the genesis of the Eyjabakkajökull moraines. Firstly, a narrow, single-crested moraine ridge at the distal end of a marginal sediment wedge formed in response to decoupling of the subglacial sediment from the bedrock and associated downglacier sediment transport. Secondly, large lobate end moraine ridges with multiple, closely spaced, narrow asymmetric crests formed by proglacial piggy-back thrusting. Thirdly, a new model shows that moraine ridges with different morphologies may reflect different members of an end moraine continuum. This is true for the eastern and western parts of the Eyjabakkajökull moraines as they show similar morphological and structural styles which developed to different degrees. The former represents an intermediate member with décollement at 4-5 m depth and 27-33% shortening through multiple open anticlines that are reflected as moderately spaced symmetric crests on the surface. The latter represents an end member with décollement at about 27 m depth and 39% horizontal shortening through multiple high amplitude, overturned and overthrusted anticlines, appearing as broadly spaced symmetric crests. We propose that the opposite end member would be a moraine of multiple symmetric, wide open anticlinal crests of low amplitude. Our data suggest that the glacier coupled to the foreland to initiate the end moraine formation when it had surged to within 70-190 m of its terminal position. This indicates a time frame of 2-6 days for the formation of the end moraines.
UR - https://www.scopus.com/pages/publications/75049085739
U2 - 10.1016/j.quascirev.2009.10.004
DO - 10.1016/j.quascirev.2009.10.004
M3 - Article
SN - 0277-3791
VL - 29
SP - 484
EP - 506
JO - Quaternary Science Reviews
JF - Quaternary Science Reviews
IS - 3-4
ER -