UNCORRECTED PROOF Cosmogenic 10 Be exposure age dating across Early to Late Weichselian ice-marginal zones in northwestern Russia HENRIETTE LINGE, EILIV LARSEN, KURT H. KJÆR, IGOR DEMIDOV, EDWARD J. BROOK, GRANT M. RAISBECK AND FRANCOISE YIOU BOREAS Linge, H., Larsen, E., Kjær, K. H., Demidov, I., Brook, E. J., Raisbeck, G. M. & Yiou, F. 2006 (August): Cosmogenic 10 Be exposure age dating across Early to Late Weichselian ice-marginal zones in northwestern Russia. Boreas, Vol. 35, 00  00. Oslo. ISSN 0300-9483. Rock samples from the Kanin Peninsula and the Timan Ridge were analysed for in situ cosmogenic 10 Be for exposure age dating purposes. Crystalline rocks were sampled at four sites on the Kanin Peninsula, either from bedrock outcrops or from glacial erratics, giving overall similar 10 Be ages. Outcropping sandstone and crystalline erratics were available from three sites at the Timan Ridge. The highly weathered sandstone gives substantially younger 10 Be ages than the adjacent erratics. The exposure ages from the Kanin Peninsula suggest that the last deglaciation of this area took place between 55 and 37 10 Be kyr ago, in agreement with a preceding Kara Sea glaciation (55  45 kyr BP). The northwest coast of the peninsulawas probably just outside the maximum limit of the last Scandinavian glaciation (20  17 kyr BP). Glacial erratic exposure ages from the Timan Ridge suggest that the 55  45 kyr BP Kara Sea glaciation reached the northern part of the ridge. The exposure dates do not show conclusive evidence regarding the existence of a Timan Ridge ice cap. Henriette Linge (e-mail: henriette.linge@geo.uib.no), Bjerknes Centre for Climate Research, Alle ´gaten 55, and Department of Earth Science, University of Bergen, Alle ´gaten 41, NO-5007 Bergen, Norway; Eiliv Larsen (e-mail: eiliv.larsen@ngu.no), Geological Survey of Norway, Leiv Erikssons v. 39, NO-7491 Trondheim, Norway; Kurt H. Kjær (e-mail: kurtk@snm.ku.dk), Natural History Museum of Denmark, Geological Museum, Øster Voldgade 5  7, DK-1350 Copenhagen K, Denmark; Igor Demidov (e-mail: demidov@krc.karelia.ru), Russian Academy of Sciences, Karelian Research Centre, Institute of Geology, 11 Pushkinskaya Street, Petrozavodsk, 185610, Russia; Edward J. Brook (e-mail: brooke@geo.oregonstate.edu), Department of Geosciences, Oregon State University, Wilkinson Hall, Corvallis, OR 97331, USA; Grant Raisbeck (e-mail: raisbeck@csnsm.in2p3.fr), Franc ¸oise Yiou, Centre de Spectrome ´trie Nucle ´aire et de Spectrome ´trie de Masse, IN2P3-CNRS, Ba ˆtiment 108, F-91405 Orsay, France; received 23rd June 2005, accepted 24th March 2006. Elucidating glacial chronologies is often difficult, especially beyond the range of radiocarbon dating. In northwest Russia, a major effort has been made on the use of optically stimulated luminescence (OSL) dating (e.g. Svendsen et al. 2004; Larsen et al. 2006a). Four consecutive major glacial advances of Weichselian age have been recorded in the White Sea area of northwest Russia (Larsen et al. 2006a). These were related to the Kara Sea (100  90 kyr BP, 55  45 kyr BP), the Barents Sea (70  65 kyr BP) and the Scandinavian (20  17 kyr BP) ice sheets. Additionally, the areawas glaciated by a local ice cap (75  70 kyr BP) across the Timan Ridge (Houmark-Nielsen et al. 2001; Kjær et al. 2003). Differentiation between individual ice sheets is based on various ice-flow indicators (Larsen et al. 1999, 2006a; Kjær et al. 2001, 2003). Between till beds there is a variety of sediments representing ice-free periods (Houmark-Nielsen et al. 2001; Lysa ˚ et al. 2001; Kjær et al. 2003; Jensen et al. 2006; Larsen et al. 2006a, b), and a composite Weichselian stratigraphy is established (Houmark-Nielsen et al. 2001; Kjær et al. 2003; Demidov et al. 2004; Larsen et al. 2006a). The relative chronology in this composite stratigraphy is based on ice-flow indicators, Eemian and Middle Weichselian marine marker beds (Devyatova 1982; Funder et al. 2002; Kjær et al. 2003; Jensen et al. 2006), and absolute ages are given by OSL dates (Larsen et al. 2006a; Thomas et al. 2006). The lateral extent of the various glacial advances is obtained by mapping of landforms and spatial distribution of till sheets (Astakhov et al. 1999; Larsen et al. 1999, 2006a; Demidov et al. 2004; Svendsen et al. 2004). There are, however, uncertainties both in terms of ice-sheet spatial distribution and chronology, and there are large area overlaps of reconstructed ice-disperse stages (Larsen et al. 2006a). Furthermore, there are some disagreements between these reconstructions (Larsen et al. 2006a) and those from the adjoining area to the east (Svendsen et al. 2004), mainly concerning the existence, timing and extent of Early Weichselian ice-dammed lakes and of the Timan Ridge ice cap. In the Pechora Lowland, east of the Timan Ridge, the ice-dammed Lake Komi existed between 100 and 80 kyr ago, and its shorelines have been mapped westwards through a lower point on the Timan Ridge (Astakhov et al. 1999). As such an extensive shoreline setting is not found west of the Timan Ridge (Houmark-Nielsen et al. 2001; Lysa ˚ et al. 2001; Kjær et al. 2003; Larsen et al. 2006a), it has been suggested that the shorelines and sediments were destroyed by a 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 C:/3B2WIN/temp files/SBOR41_S100.3d[x] Tuesday, 23rd May 2006 15:22:6 DOI 10.1080/03009480600781909 # 2006 Taylor & Francis