|
As the Keewatin and Patrician ice-sheets retreated by melting, the broken rock material held within them was deposited as outwash plains and moraines. Where this material was released into the lake waters spreading in front of the ice-sheet, scattered deposits of stratified sand and gravel were laid down. These deposits were later covered by lake clays. Where this material was deposited on land, a layer of unsorted drift or boulder till, composed of a mixture of boulders, gravel, sand, clay, and silt, was formed. |