GEOPHYSICAL AND SEDIMENTOLOGICAL INVESTIGATIONS OF MULTI-RIDGE ESKER COMPLEXES IN THE CHILCOTIN REGION, BRITISH COLUMBIA

Multi-ridge esker complexes have been reported as meltwater features of the Cordilleran, Laurentide, and Fennoscandian Ice Sheets. However, multi-channel drainage configurations are theoretically unlikely under thick ice and steady-state water flows, and despite their commonality in deglacial landscapes, no unifying theory has been proposed for the formation of multi-ridge esker complexes. Previous research suggests that these planforms are associated with some combination of very high flows, sediment clogging tunnels, and/or crevasse-fill in thin ice, but the empirical evidence to support these hypotheses is largely lacking.

Field studies of several multi-ridge esker complexes were undertaken in the Chilcotin Region of British Columbia. Geomorphic mapping from a high-resolution LiDAR digital elevation model was used to characterize ridge morphology and associated landforms. Geophysical surveys (ground penetrating radar and electrical resistivity tomography) targeting ridge junctions were supplemented by sedimentological techniques at exposures and test pits to characterize ridge internal composition and architecture. Together, these data show sedimentary architecture consistent with synchronous operation of tunnels under high magnitude (flood) flows. The results of this research provide some of the first empirical observations of multi-ridge esker complexes, allowing for more precise inferences of paleo-glacial hydrologic processes.