The area contains 80 to 275 feet of sediment deposited on a southward sloping Palaeozoic and Jurassic bedrock surface. Three tills are present with stratified units above and below each and a fluvial unit overlying the uppermost stratified unit. The upper till forms an asymmetric ridge in the northern one-third of the area. The tills are carbonate rich loams and clay loams. The lower till and middle and lower stratified units were deposited prior to the last ice advance and the middle and upper till by the ice which melted to form Glacial Lake Agassiz. Lacustrine and prodeltaic units were deposited in Lake Agassiz and the fluvial unit after the lake drained.