WIDESPREAD PLEISTOCENE SUBMERGENCE. .°>19 



and I have never seen in the Leda clay the assemblage of forarainiferal forms 

 now dredged from 200 to 300 fathoms in the Gulf of St. Lawrence. 



I infer that the subsidence of the Leda clay period and of the interglacial 

 beds of Ontario belongs to the time of the sea beaches from 450 to 600 

 feet in height, which are so marked and extensive as to indicate a period of 

 repose. In this period there were marine conditions in the lower and middle 

 St. Lawrence and in the Ottawa valley, and swamps and lakes on the upper 

 Ottawa aud the western end of Lake Ontario ; and it was at this time that the 

 plants described in this paper occupied the country. It is quite probable, 

 nay certain, that during this interglacial period re-elevation had set in, since 

 the upper Leda clay and the Saxicava sand indicate shallowing water, and 

 during this re-elevation the plant-covered surface would extend to lower 

 levels. 



This, however, must have been followed by a second subsidence, since the 

 water-worn gravels and loose, far-traveled bowlders of the later drift rose 

 to heights never reached by the till or the Leda clay, and attained to the 

 tops of the highest hills of the St. Lawrence valley, 1,200 feet in height, and 

 elsewhere to still greater elevations. This second bowlder drift must have 

 been wholly marine, and probably not of long duration. It shows no 

 evidence of colder climate than that now prevalent, nor of extensive glaciers 

 on the mountains; and it was followed by a paroxysmal elevation in succes- 

 sive stages till the land attained even more that its present height, as subsi- 

 dence is known to have been proceeding in modern times. 



The above sequence applies to the districts of Ontario, Quebec, the arctic 

 coast, aud the maritime provinces, and might be illustrated by a great 

 accumulation of facts ; but these may be found in papers published in the 

 Canadian Naturalist and the Canadian Record of Science and in the reports 

 of the Geological Survey, more especially those by Dr. G. M. Dawson, Mr. 

 Chalmers, aud the writer. 



For the region between the great lakes and the Rocky Mountains and for 

 the Pacific coast the sequence is similar, but either the interior region has 

 experienced a greater elevation or the times must have been somewhat 

 different. In the mountainous regions of the west, also, more especially 

 in the interior of British Columbia, the evidence of .great local glaciers is 

 much more pronounced than on our lower mountains of the east* 



I am quite aware that the above sequence and the causes assumed are 

 somewhat different from those held by many geologists with reference to 

 regions south of Canada, but must hold that they are the only rational con- 

 clusions which can be propounded with reference to the facts observed from 

 the parallel of 45° to the Arctic ocean. 



*G. M. Dawson, Superficial Geology of British Columbia: Quart. Jour. Geol. Soc, vol. 34, 1878, p. 

 89, et seq.; ibid, vol. 37, 1881, p. 272, et seq. 



XLII— Bull. Geol. Soc. Am., Vol. 1, 1889. 



