RECURRENCE AND FLOW DIRECTION OF THE CORDILLERAN ICE SHEET (CIS) ACROSS THE KAWDY PLATEAU, NORTHERN BRITISH COLUMBIA

While extensive research has constrained the timing of advances and retreats of the North American ice sheet, less is known about the development and fluctuations of the Cordilleran ice sheet (CIS). The Kawdy Plateau (KP), located in the Dease Lake area of northern British Columbia, is an ideal place to constrain the timing and minimum thickness of the CIS. Evidence for glaciation on the plateau includes six identified glaciovolcanic features (Kawdy Mountain, Tutsingale Mountain, Nuthinaw Mountain, Meehaz Mountain, Tanker tuya, Horseshoe tuya) as well as one very distinct cirque and an extensive field of glacial scours striking between 21-92° across the plateau floor and the tops of at least two of the tuyas. These scours, which appear to cluster into at least three separate groups with unique orientations, may indicate the presence of up to three separate glaciers flowing in slightly different directions over the KP, separated by enough time to allow the previous glacier to melt entirely and expose the plateau floor to continued erosion. Cross-cutting relationships and quality of preservation indicate that the group striking between 88-92° across the plateau and tuyas is the oldest, the group striking 21-59° is younger than that, and a group striking 60-88° is the youngest. Drumlinoid features on the plateau floor and on top of Horseshoe Tuya indicate that despite ~70 degrees in variation of orientation direction of scours across the entire area, the ice sheets acting in this area always flowed in an east-to-west or northeast-to-southwest direction. The observation of these different groups, as well as alpine glacial features like the cirque on Horseshoe Tuya, is most consistent with the hypothesis that the CIS did fluctuate extensively in size during the Pleistocene, between periods of thick, low-elevation ice cover and periods of more sparse, high-elevation cover or even complete absence of ice. Evidence for multi-stage continental glaciation has important implications for the reconstruction of the history of the CIS, as well as for the paleoclimate factors that controlled its development.