Deposition As Cold-Climate Loess, Duvanny Yar, Northeast Siberia
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This is a repository copy of Palaeoenvironmental Interpretation of Yedoma Silt (Ice Complex) Deposition as Cold-Climate Loess, Duvanny Yar, Northeast Siberia. White Rose Research Online URL for this paper: http://eprints.whiterose.ac.uk/99922/ Version: Submitted Version Article: Murton, J.B., Goslar, T., Edwards, M.E. et al. (15 more authors) (2015) Palaeoenvironmental Interpretation of Yedoma Silt (Ice Complex) Deposition as Cold-Climate Loess, Duvanny Yar, Northeast Siberia. Permafrost and Periglacial Processes, 26 (3). pp. 208-288. ISSN 1045-6740 https://doi.org/10.1002/ppp.1843 Reuse Unless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version - refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher’s website. Takedown If you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing [email protected] including the URL of the record and the reason for the withdrawal request. [email protected] https://eprints.whiterose.ac.uk/ 1 1 Palaeoenvironmental interpretation of yedoma silt (Ice Complex) deposition as cold-climate loess, 2 Duvanny Yar, northeast Siberia 3 Julian B. Murtona*, Tomasz Goslarb,c, Mary E. Edwardsd,e, Mark D. Batemanf, Petr P. Danilovg, Grigoriy N. 4 Savvinovg, Stanislav V. Gubinh, Bassam Ghalebi, James Hailej,k, Mikhail Kanevskiyl, Anatoly V. Lozhkinm, 5 Alexei V. Lupachevh,n, Della K. Murtono, Yuri Shurl, Alexei Tikhonovp, Alla C. Vq, Yurij K. Vr, 6 Stephen A. Wolfes 7 8 aPermafrost Laboratory, Department of Geography, University of Sussex, Brighton BN1 9QJ, UK 9 bAdam Mickiewicz University, Faculty of Physics, Umultowska 85, 61-614 Poznan, Poland 10 cPoznan Radiocarbon Laboratory, P “ T P ‘ -612 Poznan, Poland 11 dSchool of Geography, University of Southampton, University Road, Southampton SO17 1BJ, UK 12 eAlaska Quaternary Center, College of Natural Science and Mathematics, University of Alaska-Fairbanks, 13 900 Yukon Drive, Fairbanks, AK 99775, USA 14 fDepartment of Geography, University of Sheffield, Winter Street, Sheffield S10 2TN, UK 15 gScience Research Institute of Applied Ecology of the North of North-East Federal University, 43 Lenin 16 Avenue, Yakutsk, 677007, Russia 17 hInstitute of Physicochemical and Biological Problems in Soil Sciences, Russian Academy of Sciences, ul. 18 Institutskaya 2, Pushchino, Moscow oblast, 142290 Russia 19 iGEOTOP-UQAM-McGILL, Université du Québec à Montréal, 201, Président Kennedy, Suite PK-7725 20 Montreal, QC, H2X 3Y7, Canada 21 jSchool of Biological Sciences, Murdoch University, Australia 22 kCentre for Geogenetics, Natural History Musuem of Denmark, University of Copenhagen, Øster Voldgade 23 5-7, 1350 Copenhagen K, Denmark 24 lInstitute of Northern Engineering, 306 Tanana Drive, Duckering Building, University of Alaska Fairbanks, 25 Fairbanks, Alaska 99775, USA 26 mNorth East Interdisciplinary Science Research Institute, Far East Branch Russian Academy of Sciences, 27 Magadan 685000, Russia 28 nInstitute of the Earth Cryosphere, Siberian Branch, Russian Academy of Sciences, ul. Malygina 86, Tyumen, 29 625000 Russia 30 oDepartment of Geography, University of Cambridge, Downing Place, Cambridge CB2 3EN, UK 31 pZoological Institute, Russian Academy of Sciences, Universitetskaya nab.1, Saint-Petersburg 199034, Russia 32 qFaculty of Geography, Lomonosov Moscow State University, Leninskie Gory 1, 119991 Moscow, Russia 33 rFaculty of Geography and Faculty of Geology, Lomonosov Moscow State University, Leninskie Gory 1, 34 119991 Moscow, Russia 35 sGeological Survey of Canada, Natural Resources Canada, 601 Booth Street, Ottawa, ON, K1A 0E8, Canada 36 37 *Corresponding author: Tel.: +44 1273 678293; fax: +44 1273 876513 38 E-mail addresses: [email protected] 39 40 2 41 ABSTRACT 42 Uncertainty about the geological processes that deposited syngenetically-frozen ice-rich silt (yedoma) 43 across hundreds of thousands of square kilometres in central and northern Siberia fundamentally limits our 44 understanding of the Pleistocene geology and palaeoecology of western Beringia, the sedimentary 45 processes that led to sequestration of hundreds of Pg of carbon within permafrost, and whether yedoma 46 provides a globally significant record of ice-age atmospheric conditions or just regional floodplain activity. 47 Here we test the hypotheses of aeolian versus waterlain deposition of yedoma silt, elucidate the 48 palaeoenvironmental conditions during deposition, and develop a conceptual model of silt deposition to 49 clarify understanding of yedoma formation in northern circumpolar regions during the Late Pleistocene. 50 T ‘ Y “ D Y 51 lower Kolyma River, northern Yakutia, supplemented by observations we have collected there and at other 52 sites in the Kolyma Lowland since the 1970s. We reconstruct a cold-climate loess region in northern Siberia 53 that forms part of a vast Late Pleistocene permafrost zone extending from northwest Europe across 54 northern Asia to northwest North America, and that was characterised by intense aeolian activity. 55 Five litho- and cryostratigraphic units are identified in yedoma remnant 7E at Duvanny Yar, in ascending 56 stratigraphic order: (1) massive silt, (2) peat, (3) stratified silt, (4) yedoma silt, and (5) near-surface silt. The 57 yedoma silt dominates the stratigraphy and is at least 34 m thick. It is characterised by horizontal to gently 58 undulating subtle colour bands but typically lacks primary sedimentary stratification. Texturally, the 59 yedoma silt has mean values of 65±7% silt, 15±8% sand and 21±4% clay. Particle-size distributions are bi- to 60 polymodal, with a primary mode of about 41 m (coarse silt) and subsidiary modes are 0.30.7 m (very 61 fine clay to fine clay), 35 m (coarse clay to very fine silt), 816 m (fine silt), and 150350 m (fine sand 62 to medium sand). Semi-decomposed fine plant material is abundant and fine in situ roots are pervasive. 63 Syngenetic ice wedges, cryostructures and micro-cryostructures record syngenetic freezing of the silt. An 64 age model for silt deposition is constructed from 47 pre-Holocene AMS 14C ages, mostly from in situ roots 65 and from 3 optically stimulated luminescence (OSL) ages of sand. The 14C ages indicate that silt deposition 66 extends from 19,000±300 cal BP to 50,000 cal BP or beyond. The OSL ages range from 21.2±1.9 ka near the 67 top of the yedoma to 48.6±2.9 ka near the bottom, broadly consistent with the 14C age model. 68 Most of the yedoma silt at Duvanny Yar constitutes cryopedolith (sediment that has experienced 69 incipient pedogenesis along with syngenetic freezing). Mineralised and humified organic remains dispersed 70 within cryopedolith indicate incipient soil formation, but distinct soil horizons are absent. Five buried 71 and 72 geochemical properties. Magnetic susceptibility, organic content, elemental concentrations and ratios tend 73 to deviate from average values of these parameters at five levels in the yedoma. The cryopedolith- 74 palaeosol sequence accreted incrementally upwards on a vegetated palaeo-landsurface with a relief of at 75 least several metres, preserving syngenetic ground ice in the aggrading permafrost. Pollen spectra dated to 76 between about 17,000 and 25,000 14C BP characteristically have frequencies of 2060% tree/shrub pollen 77 (mainly Betula and Pinus) and 2060% graminoids, predominantly Poaceae, plus forbs, whereas spectra 78 dated to about 30,00033,000 14C BP have lower values of woody taxa (about 10%) and are dominated by 79 graminoids (mainly Poaceae), forbs (particularly Caryophyllaceae and Asteraceae) and S. rupestris. The 80 latter are more typical of Last Glacial Maximum (LGM) samples reported elsewhere in Siberia, and the 81 unusually high arboreal pollen values in the LGM yedoma at Duvanny Yar are attributed to long-distance 82 transport of pollen. 83 Three hypotheses concerning the processes and environmental conditions of yedoma silt deposition at 84 Duvanny Yar are tested. The alluvial-lacustrine hypothesis and the polygenetic hypothesis are both 85 discounted on sedimentary, palaeoenvironmental, geocryological and palaeoecological grounds. The 86 loessal hypothesis provides the only reasonable explanation to account for the bulk of the yedoma silt at 87 this site. Supporting the loessal interpretation are sedimentological and geocryological similarities between 88 the Duvanny Yar loess-palaeosol sequence and cold-climate loesses in central and northern Alaska, the 89 Klondike (Yukon), western and central Siberia and northwest Europe. Differences between loess at 90 Duvanny Yar and that in western and central Siberia and northwest Europe include the persistence of 91 permafrost and the abundance of ground ice and fine in situ roots within the yedoma. Modern analogues 92 of cold-climate loess deposition are envisaged at a local scale in cold humid climates where local 93 entrainment and deposition of loess is generally restricted to large alluvial valleys containing rivers that are 3 94 glacially-sourced or drain areas containing Late Pleistocene glacial