Climate-Controlled Glacial Erosion in the Unconsolidated Sediments of Northwestern Europe, Based on a Genetic Model for Tunnel Valley Formation

Abstract

The development of large erosive subglacial forms in unconsolidated sediments is generally attributed to the eroding power of subglacial meltwater flowing under high pressure conditions. Most explanations, however, differ in the source of meltwater and the speed at which it erodes the subglacial bed. Based on the geometry of deep tunnel valleys and glacial basins in northwestern Europe, a reconstruction of subglacial hydrological conditions during the development of subglacial depressions is made. It is demonstrated that the flow of subglacial meltwater in subglacial channels under high glaciostatic pressures is only capable of eroding large volumes of sediment as long as there is imminent glaciohydrological instability. For the thick aquifers in northwestern Europe, this instability is achieved when large quantities of supraglacial meltwater are available. Furthermore, a theoretical definition is given for maximum depression depth to be reached by subglacial erosion. It is shown that this maximum depth is strongly related to average air temperatures during deglaciation and that glacier bed lowering is to be expected during any final phase of glaciations. The theoretical framework presented enables a tentative comparison between large-scale glacial morphology of different glaciations in northwestern Europe.

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

“…The spatial and temporal organisation (i.e., advancing and then retreating ice fronts) of this plurikilometric-scale erosional depression and subsequent infill conforms to a glacial basin model (Van der Wateren, 1994; 'tectonic basin' of Boulton and Caban, 1995;Van Dijke and Veldkamp, 1996). Such a basin is frequently recognised at the rear of glaciotectonic complexes also called "terminal or push moraines" (Fig.…”

“…15b). The main part of the material stacked in the down-ice foldand-thrust belt is generally thought to have been removed from the substrate over a décollement plane through subglacial shortening in conditions of high mechanical coupling between an advancing ice front and the proglacial sediments ( Van der Wateren, 1994;Boulton and Caban, 1995;Van Dijke and Veldkamp, 1996;Bennett, 2001;Bennett et al, 2004). In such a scenario, accommodation for subsequent ice-marginal to proglacial sediment deposition is then made available since the onset of the glacial retreat.…”

“…Tunnel valleys fed contemporaneous proglacial deeply-incised channels, connecting the subglacial drainage network to the proglacial delta; 2 -The subsequent ice-front recession then resulted in the infill of the glacial basin typically including high-energy depositional facies. (b) Illustration of the coeval formation of both a glacial basin and a large-scale glaciotectonic deformation, after Van Dijke and Veldkamp (1996). (c) Location (red frame) of the Tihemboka ice-front zone in the context of an Upper Ordovician ice-marginal environment (Upper Glaciogenics, see Fig.…”

A comparison of helicopter-borne electromagnetics in frequency- and time-domain at the Cuxhaven valley in Northern Germany

“…The genesis of buried valleys, or tunnel valleys, are discussed by e.g. Cofaigh (1996), van Dijke and Veldkamp (1996), Piotrowski (1997), Huuse and Lykke-Andersen (2000) and .…”

Pleistocene subglacial tunnel valleys in the central North Sea basin: 3‐D morphology and evolution

“…Wright, 1973;Mooers, 1989;Booth and Hallet, 1993;Patterson, 1997;Clayton et al, 1999;Cutler et al, 2002;Rains et al, 2002). In northwest Europe tunnel valleys formed during successive Pleistocene glaciations occur onshore in the UK, the Netherlands, Germany and Poland (Woodland, 1970;Cornwell and Carruthers, 1986;Ehlers and Linke, 1989;Piotrowski, 1994;van Dijke and Veldkamp, 1996;Dobracki and Krzyszkowski, 1997), and offshore in the UK, Dutch, German and Danish North Sea (Dingle, 1971;Jansen, 1976;Cameron et al, 1987;Ehlers and Wingfield, 1991;Praeg, 1996Praeg, , 2003Huuse and LykkeAndersen, 2000;Kluiving et al, 2003) and Irish Sea (Eyles and McCabe, 1989;Wingfield, 1989) basins. Thus far, few possible tunnel valleys have been documented from the former glaciated margins of Antarctica, although this may be a function of the fact that most research to date has concentrated on parts of the Antarctic shelf that exhibited ice-streaming behaviour (e.g.…”