Retreat pattern of the <scp>C</scp>ordilleran <scp>I</scp>ce <scp>S</scp>heet in central <scp>B</scp>ritish <scp>C</scp>olumbia at the end of the last glaciation reconstructed from glacial meltwater landforms

Abstract

The C ordilleran I ce S heet ( CIS ) covered much of the mountainous northwestern part of N orth A merica at least several times during the P leistocene. The pattern and timing of its growth and decay are, however, poorly understood. Here, we present a reconstruction of the pattern of ice‐sheet retreat in central B ritish C olumbia at the end of the last glaciation based on a palaeoglaciological interpretation of ice‐marginal meltwater channels, eskers and deltas mapped from satellite imagery and digital elevation models. A consistent spatial pattern of high‐elevation (1600–2400 m a.s.l.), ice‐marginal meltwater channels is evident across central B ritish C olumbia. These landforms indicate the presence of ice domes over the S keena M ountains and the central C oast M ountains early during deglaciation. Ice sourced in the C oast M ountains remained dominant over the southern and east‐central parts of the I nterior P lateau during deglaciation. Our reconstruction shows a successive westward retreat of the ice margin from the western foot of the R ocky M ountains, accompanied by the formation and rapid evolution of a glacial lake in the upper F raser R iver basin. The final stage of deglaciation is characterized by the frontal retreat of ice lobes through the valleys of the S keena and O mineca M ountains and by the formation of large esker systems in the most prominent topographic lows of the I nterior P lateau. We conclude that the CIS underwent a large‐scale reconfiguration early during deglaciation and was subsequently diminished by thinning and complex frontal retreat towards the C oast M ountains.