Study of clay sediments in the Ottawa-Hull area

The fine-grained surficial deposits that are found extensively along the Ottawa - St. Lawrence Rivers and their tributaries are frequently referred to as marine sediments. At Ottawa, there appear to be two main deposits; the lower clay is known to have had its depositional origin in the Champlain Sea, but the question arises frequently whether the so-called "upper clay" had a somewhat different depositional origin, perhaps even a fresh water environment.