The Basal Ice and Debris Sequence at the Margin of an Equatorial Ice Cap; El Cotopaxi, Ecuador

Resumen

The basal ice sequences of two glaciers descending from the equatorial ice cap of El Cotopaxi, Ecuador, comprise several metres of debris-rich ice. Up to 4m of ‘stratified’ ice and debris are attributed to the freezing of basal meltwater to the glacier sole close to the margin. The thickness of this layer is related to the permeability of the sub-strate, which determines the meltwater supply at the margin. Debris bands up to 10cm thick in the basal sequence are attributed to thrusting induced by compressive flow. ‘Dispersed facies’ regelation ice is not present at the site, indicating that the basal environment in the interior is not one of stable pressure-melting/regelation conditions, but probably one of continuous melting. The entrainment and stacking of basal debris occurs over a very short distance, close to the margin.