Stable Isotopes and Debris in Basal Glacier Ice, South Georgia, Southern Ocean

Abstract

This paper combines a study of the rock debris and δD/δ18O isotopic characteristics of basal ice sequences in three representative glaciers in South Georgia and concludes that the debris and ice has been entrained mainly by basal freezing. The size distribution of the rock debris is typical of crushing and abrasion, and reflects transport at the ice–rock interface. The δD/δ18O relationships show that clear ice associated with the debris has accreted through freezing. The white bubbly glacier ice has δD/δ18O relationships typical of precipitation which demonstrates an altitudinal effect between glaciers.

Debris entrainment and landform genesis during tidewater glacier surges

“…The characteristics of the banded subfacies are also consistent with refreezing at the glacier base, producing thin, discontinuous layers of alternating debris-rich and clean ice [Sugden et al, 1987;Sharp et al, 1994;Hubbard and Sharp, 1995;Waller et al, 2000;Larsen et al, 2010]. This can indicate a freeze-on [Weertman, 1961] and/or regelation [Hubbard and Sharp, 1993] origin.…”

“…Dispersed ice and the descriptively similar facies termed "clotted" [Knight, 1987;Sugden et al, 1987] and "clear" [Sharp et al, 1994;Hubbard and Sharp, 1995;Hubbard et al, 2000] in previous studies are typically interpreted to have formed through either sedimentary [e.g., Lawson, 1979;Knight, 1987;Sugden et al, 1987] in close proximity to the glacier bed and/or debris-rich basal ice. The very clear, bubble-poor nature of much of this facies is consistent with the expulsion of gas during ice deformation [Hubbard and Sharp, 1995].…”

“…The properties and character of this debris-rich ice can provide an insight into processes occurring at the glacier bed, particularly in relation to sediment entrainment [e.g., Lawson, 1979;Sugden et al, 1987;Alley et al, 1997], and therefore offer great potential for investigating basal conditions at surge-type glaciers. Numerous ice facies with differing physical characteristics have been described from the base of glaciers and ice sheets [see Hubbard et al, 2009].…”

Lithofacies analysis of the Catfish Creek till: Bradtville, Ontario

“…The presence of faceted striated clasts, bimodal sediment peaks at -4d> and 7<b and preferred pebble fabric alignment imply Diamicts 1-4 (Dmm) have a basal glacigenic origin (Boulton, 1978;Sugden et al" 1987). In addition, stratigra phic relationships (Fig.…”

“…Various sedimentologic techniques, including analysis of in situ pebble fabrics, granulometric distributions and clast shapes, have been employed to demonstrate glacial transport paths and depositional environments (Boulton, 1978;Sugden et al, 1987). In the Bradtville area, Dreimanis et al (1987) and others have used lithological content and limestonedolomite ratios to determine stratigraphic relationships of local glacial sequences.…”