Presentation by Dr. Alex Sodeman.
The Deglaciation of the Cordilleran Ice Sheet on the Southern Fraser Plateau of British Columbia, Canada: New Insights from Paleo Subglacial and Proglacial Landforms
Abstract:
The nature of Cordilleran Ice Sheet (CIS) deglaciation over the central interior of British Columbia, Canada, is debated, one hypothesis suggesting the CIS underwent widespread top-down melting and stagnation due to rapid change in the ELA, and another suggesting an active margin was maintained throughout deglaciation. Recent releases of high-resolution elevation data obtained from LiDAR surveys have revealed a wide range of previously unidentified landforms potentially linked to CIS deglaciation, allowing for a more detailed study to test these competing hypotheses. This study focuses on the deglaciation of the southern Fraser Plateau located in south-central British Columbia, where a series of subglacial and proglacial landforms have been identified using the LiDAR surveys. Detailed morphological, sedimentological, and near-surface geophysical surveys of the subglacial landforms, which include triangular-shaped "murtooized terrain" and palimpsest subglacial meltwater corridors, indicates the CIS had an active subglacial environment during deglaciation. However, the preservation of these delicate subglacial landforms indicates the overlying ice must have melted in place. The proglacial landforms identified include wave-cut benches, glacial lake outburst flood spillways, perched deltas, and grounding line moraines, which together were used to reconstruct glacial lakes Dog and Hache. The distribution of proglacial landforms suggests initially rapid melting of dead ice and the rapid release of lake water through glacial lake outburst floods until the eventual establishment of a stable grounding line. Together, these landforms suggest a complex local deglacial history with periods of active margin retreat separated by significant local top-down melting.
