Marginal-marine glacial sedimentation in the late Precambrian succession of East Greenland

Abstract

The late Precambrian succession of the fjord region of East Greenland is characterized by two glacigenic formations. The lower one, the Ulvesø Formation, rests on different members of the Limestone-Dolomite ‘series’ (Eleonore Bay Group), and comprises diamictite, conglomerate, sandstone, and rhythmite, all with a high dolomite content. Few beds can be traced for more than a few hundred metres, and erosional breaks are sometimes present. Clasts are predominantly intrabasinal. A turbiditic dolomitic sandstone-mudstone succession, the Arena Formation, lies above. The upper glacigenic horizon, the Storeelv Formation, contains a similar range of facies as the Ulvesø Formation, but is less dolomitic and contains exotic gneiss, granite and volcanic clasts, as well as intrabasinal carbonates. The Ulvesø and Storeelv formations contain facies characteristic of a low-level terrestrial to marine glacial environment, including: basal tillite, waterlain tillite, debris-flow deposits, ice proximal to distal glacimarine sediments, glaciolacustrine and glacimarine rhythmites with ice-rafted material, permafrost features, aeolian sands and evaporites. The bulk of the glacigenic sediment appears to have been associated with an ice sheet of continental proportions, which in terms of its thermal regime was probably below the pressure melting point but sliding on its bed. Our interpretation of large parts of the succession as waterlain till implies that floating, debris-bearing ice was an important part of the system, probably in the form of outlet glaciers or ice streams, coalescing as an ice shelf in a tectonically controlled marine basin beyond an irregular coastline. Considerable current activity, both beneath the ice shelf, and sedimentation controlled by iceberg drifting in distinct lanes existed. The succession further illustrates the response of glacimarine sedimentation to ice-retreat onto land, with marked changes from facies with obvious glacial affinities to those devoid of them.

Sedimentary imprints of former ice-sheet margins: Insights from an end-Ordovician archive (SW Libya)

“…In contrast with the well-known relic scour marks made by icebergs, or with thaw lakes resulting from the disintegration of continuous permafrost, which together form km-scale structures, the illustrated examples from the ice-marginal case study are on a much smaller scale (cm-, dm-to m-scale). It is worth noting that the Phanerozoic periglacial record is relatively scant -or underestimated at this time -if compared to the glacial record, with some exceptions (Krull, 1999;Pachur and Altmann, 2006;Hambrey et al, 2007;Jones and Fielding, 2008), which are interestingly more frequent in the Neoproterozoic record (Deynoux, 1982;Fairchild and Hambrey, 1984;Moncrieff and Hambrey, 1990;Maloof et al, 2002 and references therein). In the end-Ordovician, some lithalsa-like and pingo structures are documented, but are paradoxically associated with time-transgressive, deglaciation deposits (Nutz et al, 2013).…”

“…Preserved glacial landsystems that have contributed to their characterisation in the Quaternary record (Shaw et al, 2000;Boulton et al, 2001;Lajeunesse and Allard, 2002;Ottesen et al, 2005;Boulton and Hagdorn, 2006;Occhietti, 2007;Evans, 2009;Winsemann et al, 2009;Jakobsson et al, 2012) are usually lacking for the identification of pre-Pleistocene ice-marginal systems. This is a severe limitation in our capacity to untangle former ice-sheet extents in deep time and in our capacity to propose sequence stratigraphic scenarios for related recessional ice-front development, whose associated deposits are nevertheless amongst the most abundant in the Earth glacial sedimentary record (Moncrieff and Hambrey, 1990;dos Santos et al, 1996;Von Brunn, 1996;Le Heron et al, 2006;Ghienne et al, 2007b). Ice-marginal depositional systems are of considerable economic importance as related deposits are genetically linked with groundwater reservoirs in Europe (e.g., Burval working group, 2009) or with gravel and sand quarries in Europe and America (e.g., Cutler et al, 2002;Winsemann et al, 2007) and are part of glaciogenic Palaeozoic or older petroleum systems in the Middle East and North Africa (Davidson et al, 2000;Bechstädt et al, 2009;Le Heron et al, 2009;Lottaroli et al, 2009;Roussé et al, 2009;Craig et al, 2013).…”

Neoproterozoic Glaciated Basins: A Critical Review of the Snowball Earth Hypothesis by Comparison with Phanerozoic Glaciations

“…1d), wave-rippled sandstones (Williams, 1996;Allen et al, 2004;Fig. 1E), and periglacial involutions (Hambrey & Spencer, 1987;Moncrieff & Hambrey, 1990). These features are easily explained as a result of Cenozoic-style climate variability over glacialinterglacial transitions, although they could equally be applied to the growth or recessional phases of a Snowball Earth-type glaciation.…”

Neoproterozoic glaciation in the Earth System

“…Many sections show evidence of phases of relative ice advance and retreat (Spencer 1971;Lindsay 1989;Leather et al 2002). Close analogies with modern glacial environments of various thermal regimes have been suggested: ranging from high sedimentation rates of the Neogene glacimarine Gulf of Alaska setting (Eyles & Eyles 1983), to ice-stream-fed ice shelves of parts of the modern Antarctic margin (Moncrieff & Hambrey 1990;Fig. 4c), to the hyper-arid Dry Valleys of Antarctica (Fairchild et al 1989).…”

“…For example, the absence of pelagic calcifiers in the Precambrian means that there was no buffering of atmospheric CO 2 by variable dissolution of Eisbacher (1985), Aitken (1991a), Eyles (1993) and Eyles & Januszczak (2004). (c) Sedimentation model illustrating coarsening-upwards succession from laminites to diamictites of different types resulting from the advance of a marine ice front, based on Neoproterozoic examples from East Greenland (after Moncrieff & Hambrey 1990). …”