. The story of the earth and man [microform]. Geology; Paleontology; Man; Géologie; Paléontologie; Homme. 274 THE STOEY OP THE EARTH AND discussion lias had reference to thoin. But it would be unfair not to inform the reader that this succession of deposits after all belon 's to the margins of our con- tinents rather than to their great central areas. This is the case at least in North America, where in the region of the great lakes the oldest glaciated surfaces are overlaid by thick beds of stratified clay, without marine fossils, and often without either stones or boulders, though thes
. The story of the earth and man [microform]. Geology; Paleontology; Man; Géologie; Paléontologie; Homme. 274 THE STOEY OP THE EARTH AND discussion lias had reference to thoin. But it would be unfair not to inform the reader that this succession of deposits after all belon 's to the margins of our con- tinents rather than to their great central areas. This is the case at least in North America, where in the region of the great lakes the oldest glaciated surfaces are overlaid by thick beds of stratified clay, without marine fossils, and often without either stones or boulders, though these sometimes occur, especially toward the north. The clay, however, contain^, drifted fragments of coniferous trees. Above this clay are sand and gravel, and the principal deposit of travelled stones r-nd boulders rests on these. I cannot affirm that a similar succession occurs on tho great inland plains of Europe and Asia; but I think it probable that to some extent it does. The ex- planation of this inland drift by the advocates of a great continental glacier is as follows: (1) In the Pliocene period the continents were higher than at present, and many deep valleys, since filled up, wero cut in them. (2) In the Post-pliocene these elevated continents became covered with ice, by the movement of which the valleys were deepened and the surf^jces striated. (3) This ice-period was followed by a depressioi and submergence, in which the cJays were deposited, filling up old channels, and much changing the levels of the land. Lastly, as the land rose again from this submergence, sand and gravel were deposited, an(? oulders scattered over the surface by floating Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Dawson, J. W. (John William), Sir, 1820-1899. Toronto : Copp Clark
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