Sediments were cored in the Cascadia basin as far south as 44 degrees 10' N. Uniform distribution of sand grains and pebbles in clay indicate ice-rafting as the depositional mechanism. Clay mineralogy and pebble petrology suggest that the provenance was the Puget Lowland and adjacent mountains in Washington and British Columbia. The distribution of the glacial marine deposits indicates that Pleistocene circulation must have been very similar to that of today. Icebergs could have been carried south by the portion of the West Wind Drift that intrudes into the area of Vancouver Island and then moves southward along the coast. As the ice melted, it left a trail of debris 400 km south of the previously believed boundary for these deposits.