Basal ice facies and supraglacial melt-out till of the Laurentide Ice Sheet, Tuktoyaktuk Coastlands, western Arctic Canada

https://doi.org/10.1016/j.quascirev.2004.06.008Get rights and content

Abstract

Glacially-deformed massive ice and icy sediments (MI–IS) in the Eskimo Lakes Fingerlands and Summer Island area of the Tuktoyaktuk Coastlands, western Arctic Canada, show, in the same stratigraphic sequences, features characteristic of both basal glacier ice and intrasedimental ice. Basal-ice features comprise (1) ice facies and facies groupings similar to those from the basal ice layers of contemporary glaciers and ice sheets in Alaska, Greenland and Iceland; (2) ice crystal fabrics similar to those from basal ice in Antarctica and ice-cored moraines on Axel Heiberg Island, Canada; and (3) a thaw or erosional unconformity along the top of the MI–IS, buried by glacigenic or aeolian sediments. Intrasedimental ice consists of pore ice and segregated ice formed within Pleistocene sands deposited before glacial overriding. The co-existence of basal and intrasedimental ice within the MI–IS records their occurrence within the basal ice layer of the Laurentide Ice Sheet. Stagnation of the ice sheet and melt-out of till from the ice surface allowed burial and preservation of the basal ice layer on a regional scale. The widespread occurrence of supraglacial melt-out till with clast fabrics similar to those in the underlying ice suggests that such till can be well preserved during partial thaw of a continental ice sheet in lowlands underlain by continuous permafrost.

Introduction

Glaciated lowlands in western Arctic Canada and northwestern Siberia contain many bodies of massive ice and icy sediments. Icy sediments contain excess ice, usually in the form of multiple ice lenses (Rampton and Mackay, 1971), and have a gravimetric ice content of less than 250%, whereas massive ice usually forms large, tabular bodies and has an ice content exceeding 250% (Harris et al., 1988). The distinction between massive ice and icy sediments, however, can be difficult to apply to complex stratigraphic sequences whose ice contents vary greatly over horizontal and vertical distances of a few metres or less as a result of glacial disturbance. Such glacially-deformed sequences can be described generally as massive ice and icy sediments (MI–IS) and specifically in terms of ice facies (cryofacies), as outlined in this paper.

MI–IS within glacial limits in Canada and Siberia have usually been interpreted either as buried glacier ice or as intrasedimental ice (ice formed within pre-existing sediment; Mackay and Dallimore, 1992). Distinguishing between them is fundamental to understanding the origin of massive ice, the interactions between glaciers and permafrost, and the history of Pleistocene ice sheets. However, interpretation of MI–IS is often problematic (Vtyurin and Glazovskiy, 1986, French and Harry, 1990), because intrasedimental ice may be difficult to distinguish from basal glacier ice, since both ice types can form by the same freezing processes (cf. Mackay, 1989). Thus the extent and relative importance of buried ice and intrasedimental ice remain uncertain. In addition, the possibility of widespread preservation of basal ice from the Laurentide Ice Sheet (LIS) merits scrutiny given (1) the growing consensus, albeit based on limited ice exposures, that buried Laurentide ice is widespread within large moraine belts, hummocky till and glaciofluvial deposits in western Arctic Canada (Sharpe, 1992, Dredge et al., 1999, St-Onge and McMartin, 1999, Dyke and Savelle, 2000) and (2) the suggestions that buried ice from the Barents-Kara Ice Sheet has been widely preserved for c. 80–90 ka in northwestern Siberia (Kaplyanskaya and Tarnogradskiy, 1986, Astakhov and Isayeva, 1988, Svendsen et al., 2004) and that buried ice of Miocene age has been preserved in southern Victoria Land, Antarctica (Marchant et al., 2002).

A new approach to describing MI–IS and interpreting their origin is to distinguish individual ice facies, based on the physical characteristics of the ice and sediment, and compare them with facies from intrasedimental massive ice and contemporary basal glacier ice. Hubbard and Sharp (1995), for example, have proposed a genetic classification for the basal ice facies of Alpine glaciers, each facies being attributed to distinctive basal conditions and processes. In contrast, classification and genetic interpretation of MI–IS facies have not yet been attempted.

This paper discusses glacially-deformed MI–IS inside the limit of the LIS in the Tuktoyaktuk Coastlands of western Arctic Canada (Fig. 1). The objectives are (1) to distinguish the individual ice facies of MI–IS; (2) to compare them with contemporary basal ice and englacial ice from Greenland, Alaska and Iceland, and with intrasedimental massive ice from Canada, in order to interpret their origin; and (3) to examine the cryostratigraphic, sedimentological and genetic relationships between MI–IS and overlying till. We conclude that basal Laurentide ice buried by supraglacial melt-out till is widely preserved in the Tuktoyaktuk Coastlands.

Section snippets

The study area

The Tuktoyaktuk Coastlands form part of the Arctic Coastal Plain between the Mackenzie Delta and Amundsen Gulf, Northwest Territories (Fig. 1). They are in the zone of continuous permafrost.

Methods

Sedimentological logging and sketching of large stratigraphic sections were carried out to determine the cryostratigraphic setting of the MI–IS. Particular attention was given to establishing (1) the cryostructures and cryofacies (Murton and French, 1994), (2) the nature and origin of the upper and lower contacts of the MI–IS, and (3) the stratigraphic and sedimentological relationships between diamicton dispersed within the MI–IS and the diamicton above it. Volumetric ice contents were

Description of MI–IS facies

Seven facies of glacially-deformed MI–IS are distinguished according to field estimates of volumetric ice content and sediment texture (Table 1).

Melt-out till

Several lines of evidence indicate that the Toker Point till above MI–IS in the study area formed by melt-out at the ice surface, and therefore is a supraglacial melt-out till. First, the till overlies an angular unconformity formed by thaw or erosion (Murton and French, 1993, Murton and French, 1994), as discussed below. Second, the till is present above MI–IS containing dispersed diamicton, but it is absent above massive ice that is debris-free.

Third, the till has a similar texture (Fig. 5),

Basal ice layer

The widespread MI–IS in the study area show, in the same stratigraphic sequences, features common to both basal and intrasedimental ice, but differ significantly from the massive intrasedimental ice at Peninsula Point. Any explanation of these facts must therefore accommodate both ice types and apply to a regional scale.

We interpret the glacially-deformed MI–IS as remnants of the basal ice layer of the LIS. This interpretation resolves the apparent paradox of co-existing basal and

Conclusions

  • 1.

    Complex sequences of glacially-deformed massive ice and icy sediments in the study area can be described systematically in terms of cryofacies (Table 1). This description facilitates comparison with other ice-rich sequences in permafrost and glacial environments and so assists with interpreting the origin of the ice.

  • 2.

    A basal-ice origin for the MI–IS in this study is indicated by (a) ice facies and facies groupings similar to those from the basal ice layers of contemporary glaciers and ice sheets

Acknowledgements

The Natural Sciences and Engineering Research Council of Canada and the Geological Survey of Canada (GSC) supported JBM's fieldwork between 1989 and 1993 by grants to Professor H.M. French. The Leverhulme Trust and the Tyrell Fund of the Geological Society supported the project between 1998 and 2000. CW is grateful to the University of Brighton Research Support Fund, and RIW's participation was supported by the University of Greenwich. The Polar Continental Shelf Project, Natural Resources

References (85)

  • G.S. Boulton

    The role of thermal regime in glacial sedimentation

  • C.R. Burn

    Cryostratigraphy, paleogeography, and climate change during the early Holocene warm interval, western Arctic coast, Canada

    Canadian Journal of Earth Sciences

    (1997)
  • S.A. Dallimore et al.

    Massive ground ice associated with glaciofluvial sediments, Richards Islands, N.W.T., Canada

  • S.R. Dallimore et al.

    Mid-Wisconsinan eolian deposits of the Kittigazuit Formation, Tuktoyaktuk Coastlands, Northwest Territories, Canada

    Canadian Journal of Earth Sciences

    (1997)
  • L.A. Dredge et al.

    Surficial materials and related ground ice conditions Slave Province, N.W.T., Canada

    Canadian Journal of Earth Sciences

    (1999)
  • A.S. Dyke et al.

    Major end moraines of Younger Dryas age on Wollaston Peninsula, Victoria Island, Canadian Arcticimplications for paleoclimate and for formation of hummocky moraine

    Canadian Journal of Earth Sciences

    (2000)
  • S.J. Fitzsimons

    Ice-marginal depositional processes in a polar maritime environment, Vestfold Hills, Antarctica

    Journal of Glaciology

    (1990)
  • H.M. French et al.

    Nature and origin of ground ice, Sandhills Moraine, southwest Banks Island, Western Canadian Arctic

    Journal of Quaternary Science

    (1988)
  • H.M. French et al.

    Observations on buried glacier ice and massive segregated ice, western Arctic coast, Canada

    Permafrost and Periglacial Processes

    (1990)
  • W.A. Gell

    Ice-wedge ice, Mackenzie Delta-Tuktoyaktuk Peninsula area, N.W.T., Canada

    Journal of Glaciology

    (1978)
  • C.D. Gribble

    Rutley's Elements of Mineralogy

    (1988)
  • N.R. Ham et al.

    Basal till fabric and deposition at Burroughs Glacier, Glacier Bay, Alaska

    Geological Society of America Bulletin

    (1994)
  • C. Harris et al.

    Englacial deltaic sediments as evidence for basal freezing and marginal shearing, Leirbreen, southern Norway

    Journal of Glaciology

    (1984)
  • Harris, S.A., French, H.M., Heginbottom, J.A., Johnston, G.H., Ladanyi, B., Sego, D.A., van Everdingen, R.O., 1988....
  • J.K. Hart

    An investigation of the deforming layer/debris-rich basal ice continuum, illustrated from three Alaskan Glaciers

    Journal of Glaciology

    (1995)
  • J.K. Hart et al.

    An investigation of debris-rich basal ice from Worthington Glacier, Alaska

    Journal of Glaciology

    (1999)
  • B. Hubbard et al.

    Basal ice formation and deformationa review

    Progress in Physical Geography

    (1989)
  • B. Hubbard et al.

    Basal ice facies and their formation in the western Alps

    Arctic and Alpine Research

    (1995)
  • Y. Iizuka et al.

    Crystal fabrics of basal ice near Hamna Icefall, East Antarctica

    Bulletin of Glaciological Research

    (2002)
  • P. Jansson et al.

    Characteristics of basal ice at Engabreen, northern Norway

    Annals of Glaciology

    (1996)
  • F.A. Kaplyanskaya et al.

    Remnants of the Pleistocene ice sheets in the permafrost zone as an object for paleoglaciological research

    Polar Geography and Geology

    (1986)
  • Klassen, R.A. 1993. Quaternary geology and glacial history of Bylot Island, Northwest Territories. Geological Survey of...
  • P.G. Knight

    Stacking of basal debris layers without bulk freezing-onisotopic evidence from West Greenland

    Journal of Glaciology

    (1989)
  • P.G. Knight

    Two-facies interpretation of the basal layer of the Greenland ice sheet contributes to a unified model of basal ice formation

    Geology

    (1994)
  • P.G. Knight

    Debris structures in basal ice exposed at the margin of the Greenland ice sheet

    Boreas

    (1995)
  • P.G. Knight et al.

    Ice faciesa case study from the basal ice facies of the Russell Glacier, Greenland Ice Sheet

  • P.G. Knight et al.

    Ice flow around large obstacles as indicated by basal ice exposed at the margin of the Greenland ice sheet

    Journal of Glaciology

    (1994)
  • Langway, C.C., 1958. Ice fabrics and the universal stage. U.S. Army Snow and Ice Research Establishment, Technical...
  • Lawson, D.E., 1979a. Sedimentological analysis of the western terminus region of the Matanuska Glacier, Alaska. CRREL...
  • D.E. Lawson

    A comparison of the pebble orientations in ice and deposits of the Matanuska Glacier, Alaska

    Journal of Geology

    (1979)
  • D.E. Lawson et al.

    Glaciohydraulic supercooling: a freeze-on mechanism to create stratified debris-rich basal iceI. Field evidence

    Journal of Glaciology

    (1998)
  • R.D. Lorrain et al.

    Isotopic evidence for relic Pleistocene glacier ice on Victoria Island, Canadian Arctic Archipelago

    Arctic and Alpine Research

    (1985)
  • Cited by (78)

    • Cryostratigraphy

      2022, Treatise on Geomorphology
    • Possible ice-wedge polygonisation in Utopia Planitia, Mars and its latitudinal gradient of distribution

      2021, Icarus
      Citation Excerpt :

      centres and margins that exhibit no discernable elevation difference, indicative of ice-wedge incipience or of a more mature and transitional stage between aggradation and degradation. Pulses of ice-complex formation have been associated with inter-and intra-glacial mean-temperature rises and falls that reach back through the Holocene epoch (e.g. Rampton and Bouchard, 1975; Rampton, 1988; Murton et al., 2005; Grosse et al., 2007; Morgenstern et al., 2013; Schirrmeister et al., 2013), to the Wisconsinan glacial stage (e.g. Rampton and Bouchard, 1975; Rampton, 1988; Murton et al., 2005; Grosse et al., 2007; Morgenstern et al., 2013; Schirrmeister et al., 2013) and, even into the earlier periods of the Pleistocene Epoch (e.g. Rampton, 1988; Kanevskiy et al., 2011). Ice-wedge polygon networks are current as well as paleo-markers of temperature variances.

    • Oriented-lake development in the context of late Quaternary landscape evolution, McKinley Bay Coastal Plain, western Arctic Canada

      2020, Quaternary Science Reviews
      Citation Excerpt :

      The Toker Point Stade limit is well defined south of the McKinley Bay Coastal Plain and appears to represent the late Wisconsinan glacial limit on the Tuktoyaktuk Peninsula. Highly deformed preglacial sediments and ground ice underlie a glacial diamicton extensively within the Toker Point Stade glacial limit along the Liverpool Bay, Nicholson Island and Eskimo Lakes regions (Mackay, 1956, 1963; Murton et al., 2004, 2005). Toker Point Till and outwash sediments, probably the Turnabout Member (Rampton, 1988), occur along the southern boundary of the McKinley Bay Coastal Plain within the upland area underlain by Kittigazuit Fm sands (Fig. 3).

    View all citing articles on Scopus

    Polar Continental Shelf Contribution Number 00904

    View full text