Page:The Journal of geology (IA journalofgeology21894univers).pdf/247
This is followed by a general view of the entire series of deposits of eastern Canada and a discussion of these, in the course of which he states the views of the origin of the deposits which are set forth more fully in a subsequent part of the book. In the course of the chapter he presents a scheme of correlation of the phenomena of the glacial period in the Cordilleran region conjointly with those of the region of the great plains (in ascending order), in which epeirogenic movements constitute the leading feature. The following is an abbreviation:
| Cordilleran Region. | Region of the Great Plains. |
|---|---|
| Cordilleran zone at a high elevation; severe glaciation; maximum development of Cordilleran glacier. | Correlative subsidence and submergence of the great plains with possible contemporaneous elevation of Laurentian axis and maximum development of the ice upon it. |
| Gradual subsidence of Cordilleran region; boulder clay of interior plateau and Yukon basin; lower boulder clay of coast region; interglacial silty beds at later stage. | Correlative elevation of western part of great plains, probably irregular; formation of extensive lakes; interglacial deposits, including peat beds. |
| Re-elevation of Cordilleran region; maximum of second glaciation. | Correlative subsidence of plains; submergence to base of Rocky Mountains; formation second boulder clay. |
| Partial subsidence Cordilleran region; formation of white silts; upper boulder clay of coast region, probably. | Correlative elevation of plains, probable formation of Missouri Coteau along shore line. |
| Renewed elevation of Cordilleran region; general amelioration, closing glacial period. | Simultaneous elevation of great plains to present levels; exclusion of the sea; formation of Lake Agassiz; gradation into present period. |
Sir William Dawson would make three subdivisions of the Pleistocene period embracing (a) Earlier Pleistocene; irregular depression of the continents, with cold climate and great local glaciers; (b) Middle Pleistocene; submergence of coasts and re-elevation of interior plateaus, with milder climate—interglacial period; and (c) Later Pleistocene; submergence of plains and general ice drift with local glaciers in mountains. The succeeding thirty pages of the chapter are devoted to the description of the deposits.
The third chapter is devoted to physical and climatal conditions. In the course of this the author introduces a map to show the distribution of glaciated and unglaciated land, and of ice-laden and of ice-free