Ground penetrating radar of lakeshore spits in nothwestern Saskatchewan, Canada: variable internal structure

Ground penetrating radar (GPR) field experiments were carried out on three different lakeshore spits located in remote northwestern Saskatchewan, Canada. The objective was to test present ideas regarding the origin of spits, particularly thickness, depositional migration direction and lake level stability. To determine depositional processes and direction of the spits, we first identified radar facies (groups of reflection with similar patterns) which from previous experiments have shown correspond with internal sedimentary structures and facies. From the results we have identified two different depositional processes which form spits not yet reported in the literature. Big Buffalo spit (4 km long) in Peter Pond Lake shows dipping reflections near the spit end indicating active longshore processes and overwash deposits. Ted Island spit, in Churchill Lake, is a complex 350 m long spit with internal reversed cross stratification sequences which infer alternating depositional trends from two different directions. The Big Island spit in Lac Ile-a-la-Crosse forms on the south side of a dumlinoid-shaped island and is 650 m long. Reflections show a deep infilled basin between the island and spit end, as well as dipping reflections (5_9) within the recurved spit end. Loss of signal return from below the spit strata in all three spits is attributed to a lithofacies change from sand to mud or diamicton.