AGE AND ORIGIN OF ICE-CORED MORAINES IN JOTUNHEIMENAND BREHEIMEN, SOUTHERN NORWAY: INSIGHTS FROM SCHMIDT-HAMMER EXPOSURE-AGE DATING JOHN A. MATTHEWS 1 , STEFAN WINKLER 2 and PETER WILSON 3 1 Department of Geography, College of Science, Swansea University, Swansea, UK 2 Department of Geological Sciences, University of Canterbury, Christchurch, New Zealand 3 Environmental Sciences Research Institute, School of Environmental Sciences, University of Ulster, Coleraine, Northern Ireland, UK Matthews, J.A., Winkler, S. and Wilson, P., 2014. Age and origin of ice-cored moraines In Jotunheimen and Breheimen, Southern Norway: insights from Schmidt-Hammer exposure-age dating. Geografiska Annaler: Series A, Physi- cal Geography, 96, 531–548. doi:10.1111/geoa.12046. ABSTRACT. High-precision Schmidt-hammer exposure- age dating (SHD) is applied to ice-cored moraine-ridge complexes at three high-alpine glaciers in Jotunheimen and Breheimen, southern Norway. Local calibration curves were established using moraine ridges dating from the last 50 years and bedrock surfaces deglaciated ∼9700 years ago. SHD ages, with 95% statistical confidence intervals, ranged from 3920 ± 790 years to a negative (futuristic) age of –890 ± 580 years at Gråsubreen, 420 ± 700 to 260 ± 710 years at Vesle-Juvbreen and 2250 ± 450 to 1605 ± 410 years at Østre Tundradalskyrkjabreen. Negatively skewed R-value distributions were interpreted as the result of weathered boulders from reworked surfaces. This leads to the interpretation of these SHD ages as maximum estimates of moraine-ridge age. Østrem’s hypothesis (that the proxi- mal ridges are the oldest and survived being overridden many times) is rejected on the basis of our SHD ages. Although ice-cored moraine ridges resemble the flow struc- tures of rock glaciers, Barsch’s hypothesis (that these ice- cored moraine complexes are rock glaciers) is also rejected. Instead, the ice-cored moraine-ridge complexes are consid- ered to be glaciotectonic structures produced by the inter- action of polythermal glaciers and alpine permafrost over the late Holocene. All the individual ridges were essentially formed during the ‘Little Ice Age’ glacier advance from material deposited earlier by multiple neoglacial events. The considerable size of the moraine complexes is attrib- uted not only to the accumulation of material from these different events over a long period of time but also to their survival in the landscape during phases of glacier retreat when ice cores do not melt and fluvial and other destructive processes remain ineffective in the permafrost environment. Key words: ice-cored moraines, Schmidt-hammer exposure- age dating (SHD), glacier–permafrost interaction, polythermal glaciers, alpine permafrost, rock glaciers, glaciotectonics, Holocene, neoglaciation, Little Ice Age, Norway Introduction Ice-cored moraines may be defined as ice-marginal landforms (moraines) that contain a discrete body of glacier ice and/or frozen sediment emplaced by a glacier (cf. Østrem 1959; Evans 2009; Lukas 2011). This paper reconsiders the origin of the ice- cored moraines characteristic of the high-alpine zone of southern Norway in the light of the appli- cation of Schmidt-hammer exposure-age dating (SHD). These landforms were first recognised, named and investigated in detail by Gunnar Østrem in the 1950s and 1960s (Østrem 1959, 1961, 1963, 1964, 1965). He not only demonstrated the pres- ence of ice cores beneath a thin debris cover but also pointed out major differences in form and scale between these multiple-ridged, ramp-like moraines (up to ∼50 m high) and the much smaller, normally widely spaced moraine ridges produced by larger glaciers at lower altitude. He also noted the spatial concentration of ice-cored moraines in the northeastern part of Jotunheimen, an area char- acterised by higher snow lines in a relatively con- tinental climate, thereby anticipating their link with alpine permafrost. Furthermore, on the basis of radiocarbon dates obtained from dust retrieved from the ice cores, he concluded that the inner (proximal) ridges are relatively old and the outer © 2014 Swedish Society for Anthropology and Geography DOI:10.1111/geoa.12046 531