Deformation, strength and tectonic evolution of basal ice in Taylor Glacier, Antarctica

• Main Authors: Fitzsimons, Sean, Samyn, Denis, Lorrain, Regi
• Format: Other/Unknown Material
• Language: unknown
• Published: Authorea, Inc. 2023
• Subjects: Taylor Glacier; Antarc*; Antarctica
• Online Access: http://dx.doi.org/10.22541/essoar.169603571.14697365/v1

Observation and measurements of ice structure and deformation made in tunnels excavated into the margin of Taylor Glacier reveal a complex, rapidly deforming basal ice sequence. Displacement measurements in the basal ice, which is at a temperature of -18°C, together with the occurrence of cavities and slickenslides, suggests that sliding occurs at structural discontinuities within the basal zone although we cannot rule out the possibility of rapid deformation in thin zones of high shear. Strain measurements show that the highest strain rates occur in ice with average debris concentrations of 26% followed by ice with debris concentrations of around 12%. The lowest strain rates occur in clean ice that has very low debris concentrations (<0.02%). Deformation within the basal ice sequence is dominated by simple shear but disrupted by folding which results in shortening of the debris-bearing ice followed by attenuation of the folds due to progressive simple shear which generates predominantly laminar basal ice structures. About 60% of glacier surface velocity can be attributed to deformation within the 4.5 m thick sequence of basal ice that was monitored for this study, and 15% of motion can be attributed to sliding. The combination of high debris concentrations and high strain rates in the debris-bearing ice means that material transported in the basal ice is exposed to a high rates of abrasion which produces heavily striated and facetted clasts typical of temperate glaciers even though the basal ice is at a temperature of -18°C.