Oil sands in glacial till as a driver of fast flow and instability in the former Laurentide Ice Sheet: Alberta, Canada

Reconstructions of the southwestern Laurentide Ice Sheet (LIS) from geomorphology have revealed complex cross-cutting ice streams, indicative of surging and flow switching. This flow pattern and behaviour is distinct from the rest of the ice sheet where ice streams flowed radially to the ice sheet margin. Many ice streams in the southwestern sector originate around the Alberta Oil Sands (AOS). Previous reports have detected oil sands material in surficial and glacial sediments south of the AOS, demonstrating potential glacial mobilisation of the oil sands. In this study, we use geochemical fingerprinting to systematically investigate surficial sediments from the former Central Alberta Ice Stream (CAIS) flow track. We compare the geochemical signatures of 82 sediments from within and outside the CAIS limits with those of the AOS (from mines and natural exposures), using gas chromatography-mass spectrometry oil-oil correlation techniques. Our results provide geochemical evidence of glacial erosion and long-distance mobilisation of AOS producing contamination signatures in sediments throughout the CAIS flow track. The strength of the AOS signature is particularly strong in sediments along the terminating margins, to the east of Calgary and in the Cooking Lake area to the southeast of Edmonton. These results inform theoretical models of enhanced slipperiness, inspired by slippery liquid infused porous surfaces (SLIPS), whereby oil lubrication of the basal sediment influences the degree of sliding and basal deformation in the ice stream. We hypothesise that naturally occurring hydrocarbons at the basal interface exerted control on the location of the onset zone of the CAIS and surrounding ice streams in Alberta. The enhanced slipperiness caused by oil contamination may also explain ice streaming and surging in other ice sheets, such as the Barents Sea Ice Sheet, where hydrocarbons are known to have been driven to the sedimentary interface during glaciation. Many ice streams in the southwestern sector of the Laurentide Ice Sheet originate around the Alberta Oil Sands (AOS). We compared the geochemical signatures of 82 sediments from within and outside the Central Alberta Ice Stream (CAIS) limits with those of the AOS, which demonstrated geochemical evidence of glacial erosion and long-distance mobilisation of AOS throughout the CAIS flow track. These results informed theoretical models of enhanced slipperiness whereby oil lubrication enhances sliding and basal deformation in the ice stream.image