C:/3B2WIN/temp files/SBOR43_S100.3d[x] Tuesday, 23rd May 2006 14:39:17 1 The last Scandinavian Ice Sheet in northwestern Russia: ice flow patterns 2 and decay dynamics 3 IGOR N. DEMIDOV, MICHAEL HOUMARK-NIELSEN, KURT H. KJÆR AND EILIV LARSEN 4 Demidov, I. N., Houmark-Nielsen, M., Kjær, K. H. & Larsen, E. 2006 (August): The last Scandinavian Ice Sheet 5 BOREAS in northwestern Russia: ice flow patterns and decay dynamics. Boreas, Vol. 35, pp. xxxÁxxx. Oslo. ISSN 0300- 6 9483. 7 Advance of the Late Weichselian (Valdaian) Scandinavian Ice Sheet (SIS) in northwestern Russia took place after 8 a period of periglacial conditions. Till of the last SIS, Bobrovo till, overlies glacial deposits from the previous 9 Barents and Kara Sea ice sheets and marine deposits of the Last Interglacial. The till is identified by its contents of 10 Scandinavian erratics and it has directional properties of westerly provenance. Above the deglaciation sediments, 11 and extra marginally, it is replaced by glaciofluvial and glaciolacustrine deposits. At its maximum extent, the last 12 SIS was more restricted in Russia than previously outlined and the time of termination at 18Á16 cal. kyr BP was 13 almost 10 kyr delayed compared to the southwestern part of the ice sheet. We argue that the lithology of the ice 14 sheets’ substrate, and especially the location of former proglacial lake basins, influenced the dynamics of the ice 15 sheet and guided the direction of flow. We advocate that, while reaching the maximum extent, lobe-shaped glaciers 16 protruded eastward from SIS and moved along the path of water-filled lowland basins. Ice-sheet collapse and 17 deglaciation in the region commenced when ice lobes were detached from the main ice sheet. During the 18 Lateglacial warming, disintegration and melting took place in a 200Á600 km wide zone along the northeastern 19 rim of SIS associated with thick Quaternary accumulations. Deglaciation occurred through aerial downwasting 20 within large fields of dead ice developed during successively detached ice lobes. Deglaciation led to the 21 development of hummocky moraine landscapes with scattered periglacial and ice-dammed lakes, while a sub- 22 arctic flora invaded the region. 23 Igor N. Demidov (e-mail: [email protected]), Russian Academy of Sciences, Karelian Research Centre, 24 Institute of Geology, Pushkinskaya Street 11, Petrozavodsk, Russia 185910; Michael Houmark-Nielsen, Institute of 25 Geology, University of Copenhagen, Øster Voldgade 10, DK-1350, Copenhagen K, Denmark; Kurt H. Kjær, 26 University of Copenhagen, Øster Voldgade 5Á7, DK-1350, Copenhagen K, Denmark; Eiliv Larsen, Geological 27 Survey of Norway, P.O. Box 3006, N-7002, Trondheim, Norway; received 6th December 2005, accepted 27th March 2006. 28 29 The eastern flank of the Scandinavian Ice Sheet (SIS) mode of advance and decay in time and space of 30 occupied large parts of the Arkhangelsk district of the the northeastern sector of the Scandinavian Ice 31 Russian European North during the Late Weichselian Sheet have until recently been poorly documented 32 (Valdaian). Although traces left by the SIS have been (Demidov et al. 2004). 33 recognized since the turn of the last century (Ramsay In this article, a revised version of Late Weichselian 34 1911), the ice flow dynamics and distribution of ice sheet flow dynamics, deglaciation pattern and the 35 landforms and sediments generated near the eastern development of landforms is presented from the time 36 limit of the maximum extent of SIS in northern of maximum extent of the Scandinavian Ice Sheet in 37 Russia are still subjects of debate (Svendsen et al. northwestern Russia until the beginning of the Holo- 38 2004). The duration and age of the glacial maximum cene. This was achieved through a critical analysis of 39 are significantly different compared with the ice previous investigations of the Quaternary stratigraphy 40 sheet’s termination nearer to the Atlantic continental and geomorphology supported by new field observa- 41 margin. It therefore appears that the peak glaciation tions and new age constraints. Data from the northern 42 in Russia was delayed by almost 10 kyr. In southwest Arkhangelsk Region (Fig. 1), including the Kanin 43 Scandinavia this state was reached some time between Peninsula, the seashore of the Kuloi Plateau and bluffs 44 32 and 25 kyr BP (Sejrup et al. 1994, 2003; Houmark- along the Pinega River, are synthesized with previously 45 Nielsen & Kjær 2003), when SIS eventually merged published data from the Severnaya Dvina and Mezen 46 with the British Isles Ice Sheet. On the northern rivers (Larsen et al. 1999; Lysa˚ et al. 2001; Kjær et al. 47 boundary, SIS coalesced with the Barents Sea Ice 2003) (Fig. 1). From 1996 to 2002, more than 100 key 48 Sheet around 22 kyr BP (Svendsen et al. 2004, and sections with Late Pleistocene deposits were investi- 49 references therein). The exact location of the merging gated by stratigraphical, sedimentological and palaeon- 50 is less evident, largely due to a lack of mappable tological methods along well-exposed cliff sites on the 51 landforms and the restricted stratigraphical control of seashore and river banks in the Arkhangelsk Region. 52 offshore sediments.UNCORRECTED Adding to these uncertainties, the By addressing these PROOF issues we close a gap in the DOI 10.1080/03009480600781883 # 2006 Taylor & Francis C:/3B2WIN/temp files/SBOR43_S100.3d[x] Tuesday, 23rd May 2006 14:39:20 2 Igor N. Demidov et al. BOREAS 35 (2006) Fig. 1. The topography of the Arkhangelsk Region, northwest Russia. Map shows alternative configurations of the maximum extent of the last Scandinavian Ice Sheet. Numbers 1Á48 refer to investigated sections and other localities in the region. 1/Tarkhanov; 2/Krynka; 3/Madakha; 4/Ostraya; 5/Pestsovaya; 6/Konushin; 7/Konushinskaya Korga; 8/Morzhovets Island; 9/Cape Kargovsky; 10/Cape Abramovsky; 11/Koida; 12/Megra; 13/Cape Tolstic; 14 and 15/Syomzha 1&2; 16/Zaton; 17/Bychie; 18/Kulogora; 19/Ezhuga; 20/Karpogory; 21/Shilega; 22/Verkola; 23/Olema; 24/Chelmokhta; 25/Lipovik; 26/Tomasha; 27/Erga; 28/Boltinskaya; 29/Yumizh; 30/Raibola; 31/Smotrakovka; 32/Osinovskaya; 33/Ust-Padenga; 34/Koleshka; 35/Pasva; 36/Nyandoma; 37/Mosha; 38/Telza; 39/Bobrovo; 40/Trepuzovo; 41/Psaryovo; 42/Chavanga; 43/Strelnya; 44/Kumzhevaya; 45/Babia; 46/Kachkovka; 47/Iokanga; 48/Oiva; 49/Tova. Compiled from the present study, Devyatova (1969, 1982), Armand (1969) (Kola Peninsula), Larsen et al. (1999), Atlasov et al. (1978), Arslanov et al. (1984) (Dvina lowland) and Lunkka et al. (2001). 53 knowledge about the Late Weichselian glaciation elevations from 10 to 80 m a.s.l. Deep troughs in the history along the fringes of the entire last SIS. White Sea lying more than 50 m below the present sea 54 level separate the Palaeozoic sedimentary platform 55 from the Precambrian crystalline basement of the 56 Setting Fennoscandian Shield. Apart from more than 100-m- 57 deep incised valleys, the Quaternary cover is 5Á60 m 58 The study area is located on the southern and eastern thick, except for uplifted regions where strongly 59 shores of the White Sea, along the Kanin Peninsula weathered bedrock and boulder fields are present 60 and the Kuloi Plateau, and it covers the middle part of (Fig. 2). Glacigenic deposits comprising till, fluvial 61 the Pinega River and the lower part of the Mezen River and lacustrine sediments of the Late Weichselian 62 (Figs 1, 2). According to Geology of USSR (1963) Scandinavian glaciation dominate subsurface expo- 63 rugged denudation plain composed of Palaeozoic sures in the western part of the discussed region, 64 sediments is dissected by the 100Á270 m high water whereas the areas to the east were glaciated by the 65 divides of the Kuloi Plateau and the Pokshenga High- Barents and the Kara ice sheets in Early and Middle 66 land, whereas the Kanin Ridge is composed of Late Weichselian time (Kjær et al. 2003; Larsen et al. 67 Precambrian metasediments and small amounts of 2006a). 68 igneous rocks (Figs 1, 2). The Severnaya Dvina, A comprehensive review of previous investigations 69 Pinega, Mezen and Kuloi rivers and the root of the in northwestern Russia has been provided by Demidov 70 KaninUNCORRECTED Peninsula occupy extensive depressions, with et al. (2004). PROOF Ramsay (1911) recognized three till units C:/3B2WIN/temp files/SBOR43_S100.3d[x] Tuesday, 23rd May 2006 14:39:22 BOREAS 35 (2006) Last Scandinavian Ice Sheet, NW Russia 3 Fig. 2. The main Quaternary geomorphological features of the Arkhangelsk region and the position of the largest extent of the Scandinavian Ice Sheet in the Late Weichselian. Compiled from Krasnov (1971), Ganeshin et al. (1980) and Lavrov (1991). 71 separated by shell-bearing sediments, i.e. on the Kanin Peninsula led Devyatova (1969), Aseev (1974) and 72 Peninsula, at the mouth of Mezen River and on the Demidov et al. (2004) to support the contention of 73 Kuloi Plateau seashore. Using the lithology of erratic Ramsay (1911) that the SIS reached the central axis of 74 boulders, Ramsay proposed that Scandinavia and the Kanin Peninsula during the Last Glacial Maximum 75 Novaya Zemlya were centres of glaciation. Two or (LGM) (Fig. 1). From the shores of Mezen Bay, the 76 three till beds have since been recognized in the Kanin boundary of the Late Weichselian SIS has been drawn 77 Peninsula area (Kalyanov & Androsova 1933; Lyutke- southward towards Severnaya Dvina via the central 78 vich 1947; Spiridonov & Jakovleva 1961). Spiridonov & part of the Kuloi Plateau (Krasnov 1971; Legkova & 79 Jakovleva (1961) also supported the idea that the upper Schukin 1972; Ganeshin et al. 1980), although Lavrov 80 till was of Scandinavian origin. This is confirmed by (1991) slightly modified these reconstructions using 81 Kjær et al.