Champlain sea, the name applied to the extension of the gulf of St. Lawrence which, in the post-glacial period, covered the present St. Lawrence-valley and the lower part of eastern Ontario. The limits of this marine invasion are revealed by marine shells on various old beaches. See A. P. Coleman, Glacial and post-glacial lakes of Ontario (Toronto, 1922).

Source : W. Stewart WALLACE, ed., The Encyclopedia of Canada, Vol. II, Toronto, University Associates of Canada, 1948, 411p., p. 32.