A 10,300-year-old permafrost core from the active rock glacier Lazaun, southern Ötztal Alps (South Tyrol, northern Italy) Karl Krainer a, ⁎, David Bressan a , Benjamin Dietre b , Jean Nicolas Haas b , Irka Hajdas c , Kathrin Lang d , Volkmar Mair d , Ulrike Nickus e , Daniel Reidl b , Hansjörg Thies f , David Tonidandel d a Institute of Geology and Paleontology, University of Innsbruck, Austria b Institute of Botany, University of Innsbruck, Austria c Laboratory of Ion Beam Physics, ETH Zürich, Switzerland d Office for Geology and Building Materials Testing, Autonomous Province of Bolzano, Italy e Institute of Meteorology and Geophysics, University of Innsbruck, Austria f Institute of Ecology, University of Innsbruck, Austria abstract article info Article history: Received 1 August 2014 Available online 13 January 2015 Keywords: Rock glacier Lazaun Ötztal Alps Holocene drought Two cores were drilled on rock glacier Lazaun in the southern Ötztal Alps (N Italy). The average ice content of core Lazaun I is 43 vol.% and of core Lazaun II is 22 vol.%. Radiocarbon dating of plant macrofossil remains of core Lazaun I yielded ages ranging from 8960 cal yr BP at a depth of ca. 23.5 m to 2240 cal yr BP at a depth of 2.8 m, indicating that the ice near the base is approximately 10,300 yr old. The rock glacier was intact since that time and the ice persisted even during warm periods of the Holocene. An ice-free debris layer between 16.8 and 14.7 m separates the rock glacier into two frozen bodies. Inclinometer measurements indicate that both frozen bodies are active and that deformation occurs within a shear horizon at a depth of 20–25 m at the base of the lower frozen body and to a minor extent at a depth of approximately 14 m at the base of the upper frozen body. The ice-free debris layer in the middle of the Lazaun rock glacier indicates a more than five centennial long drought period, which dates to about 4300–3740 cal yr BP. © 2014 University of Washington. Published by Elsevier Inc. All rights reserved. Introduction Alpine permafrost is widespread in the European Alps with rock gla- ciers being the most common and most spectacular feature (Gärtner-Roer, 2010; Boeckli et al., 2012). In Austria, up to 2000 km 2 (ca. 2.4% of the area) is probably under permafrost conditions, i.e. under negative ground temperatures throughout the year, and contains considerable amounts of permafrost ice (Lieb, 1998). In Switzerland, about 5% of the area (~2100 km 2 ) is classified as permafrost, in South Tyrol (northern Italy) about 6% (440 km 2 ). In the past the formation of rock glaciers has been the subject of extensive debate, but now it is widely accepted that rock glaciers are either permafrost phenomena (“ice-cemented rock glaciers”) or may develop from debris-covered glaciers (“ice-cored rock glaciers”). In recent years progress has been achieved concerning the knowl- edge about the distribution of permafrost in the European Alps. Recent- ly, Haeberli et al. (2010) and Haeberli (2013) provided an overview on the relatively short history, and on the important issues and primary challenges of research on alpine permafrost. Cremonese et al. (2011) presented the first version of a permafrost inventory for the European Alps including a rock glacier inventory. Kellerer-Pirklbauer et al. (2012) compiled a rock glacier inventory for the eastern part of the Austrian Alps, Krainer and Ribis (2012) for the Tyrolean part of the Austrian Alps and Bollmann et al. (2012) for South Tyrol. More than 4500 rock glaciers were identified in the Austrian Alps. In Tyrol, western Austria, active and inactive rock glaciers cover an area of approximately 87 km 2 . Ground temperatures in mountain permafrost are measured in boreholes and with temperature loggers installed near the surface (e.g. Haeberli and Funk, 1991; Lüthi and Funk, 2001; Harris et al., 2003; Christiansen et al., 2010; Nötzli and Vonder Mühll, 2010; Nötzli et al., 2010; Schoeneich et al., 2010; Zhao et al., 2010). Nevertheless, little information exists on the amount of ice contained in rock glaciers, the age of the ice and its chemical character- istics. Hausmann et al. (2007, 2012) used geophysical methods to calcu- late the thickness, internal structure and ice content of active rock glaciers. Age-determination of rock glaciers is difficult and thus rare (summary in Barsch, 1996). Methods for absolute and relative-age dating of rock glacier surfaces are discussed by Haeberli et al. (2003). Laustela et al. (2003) measured the weathering rinds of the debris to determine the relative ages of rock glacier surfaces. Fossil (relict) Quaternary Research 83 (2015) 324–335 ⁎ Corresponding author at: Institute of Geology, University of Innsbruck, Innrain 52, 6020 Innsbruck, Austria. E-mail address: Karl.Krainer@uibk.ac.at (K. Krainer). http://dx.doi.org/10.1016/j.yqres.2014.12.005 0033-5894/© 2014 University of Washington. Published by Elsevier Inc. All rights reserved. Contents lists available at ScienceDirect Quaternary Research journal homepage: www.elsevier.com/locate/yqres