Geomorphology and sedimentology of surging glaciers: a land-systems approach

Abstract

ABSTRACT. The identification of surging glaciers and ice streams in glaciated landscapes is of major importance to the understanding of ice-sheet dynamics and for reconstructing ice sheets and climate. No single landform or diagnostic criterion has yet been found with which to identify surging glaciers. A surging-glacier land-system model is constructed using observations and measurements from contemporary surging-glacier snouts in Iceland, Svalbard, U.S.A. and Canada for differentiating ancient surging margins from other non-surging palaeoglaciers. This integrates the suite of landforms, sediments and stratigraphy produced at surging-glacier margins. Landforms produced during surging include thrust moraines, concertina eskers and subglacial crevasse-squeeze ridges. Sedimentary sequences are usually characterized by multiple stacked diamictons and stratified interbeds, which display severe glaciotectonic contortion and faulting. Hummocky moraine, comprising interbedded stratified sediments and mass-flow diamictons, has also been associated with surge margins where large quantities of supraglacial and englacial debris entrained during the surge event have melted out in situ. An example of the application of the land-system model is presented for east-central Alberta, Canada. A surging palaeo-ice stream is identified within this part of the southwestern Laurentide ice sheet, where thrust-block moraines, crevasse-squeeze ridges, flutings, hummocky moraine and glaciotectonized sediments are juxtaposed.

Sedimentary and structural evolution of a relict subglacial to subaerial drainage system and its hydrogeological implications: an example from Anglesey, north Wales, UK

“…Several studies have documented the widespread presence of buried ice and kettle structures within both contemporary and former ice-marginal to proglacial environments (Hambrey, 1984;Krüger, 1997;Evans & Twigg, 2002;Eyles et al, 2003). These reflect either the buried remnants of detached glacier snouts (Ham & Attig, 1996;Evans & Rea, 1999;Everest & Bradwell, 2003), buried ice blocks detached from within englacial or subglacial meltwater channels (Benn and Evans, 2010), or by meltwater floods such as jökulhlaups (Gustavson & Boothroyd, 1987;Maizels, 1992;Fay, 2002). The localised nature of this type of collapse structure suggests that the buried ice occurred as discrete buried blocks that possibly originated from the failure of a subglacial conduit wall or roof during the deposition of Lithofacies B.…”

Glacial geomorphology of the terrestrial margins of the tidewater glacier, Nordenskiöldbreen, Svalbard

“…Bennett et al, 1996;Evans & Rea, 1999Lovell et al, 2015) potentially originating from debris-rich englacial structures. Such debris-rich structures are often linked with surge behaviour Lønne, 2006;Roberts, Yde, Knudsen, Long, & Lloyd, 2009) and the main mechanism proposed to be responsible for their origin is squeezing of debris into crevasses (Rea & Evans, 2011); thrust faulting related to longitudinal compression Lovell et al, 2015); reorientation of vertical crevasses, which facilitates subsequent thrusting (Evans & Rea, 1999;Rea & Evans, 2011) and hydrofracturing (Denis, Buoncristiani, & Guiraud, 2009;Lovell et al, 2015;Roberts et al, 2009). However, no surge behaviour has been observed in the historical records for Nordenskiöldb-reen, which suggest that potential surge behaviour had to occur prior to 1882.…”

Satujökull glacial landsystem, Iceland

“…Sharp, 1985a;Evans and Rea, 1999;2003;Schomacker et al, 2007). Landsystem 2a documents the oldest surge, which reached the proximal slopes of the ice-cored moraine arc of Landsystem 1 in the western foreland but not the forelands of the central and eastern lobes.…”

“…Evans and Rea, 1999;2003;Evans and Twigg, 2002;Evans et al, 2006;2009). Complexity in the glacial geomorphological record occurs where contrasting landsystems are inset/nested or superimposed on the same glacier foreland due to spatial and temporal changes in glacier dynamics (e.g.…”