Chalmers — Shore Lines of the St. Lawrence Valley. 175 



Art. XXII. — The Geomorphic Origin and Development of 

 the Raised Shore Lines of the St. Lawrence Valley and 

 Great Lakes ; by R. Chalmers, LL.D., of the Geological 

 Survey of Canada. 



[Published by permission of the Acting Director of the Geological Survey.] 



In a paper published by the writer in 1896 on the "Pleisto- 

 cene Marine Shore Lines on the South Side of the St. Lawrence 

 Valley, "* and in an official report issued in 1897, t it was shown 

 that the valley referred to and the region of the Great Lakes 

 must have stood at a lower level at the close of the Pleistocene J 

 than at the present day, the movements of the ice in the glacial 

 period and the existing altitudes of the shore lines clearly prov- 

 ing this. Investigations regarding the position and elevation 

 of the shore lines of the St. Lawrence basin have been con- 

 tinued at intervals since and considerable new data obtained. 

 Very interesting observations have been made on the north side 

 of the two lower great lakes, Ontario and Erie, showing the 

 geomorphism which the region has undergone in the post- 

 glacial or recent stages of the Post-Tertiary. The following 

 notes, deduced from the field work of the last seven years, 

 are preliminary to a more detailed discussion of the results. 



High-level shore lines of marine origin fronting the St. 

 Lawrence to the north have been traced almost without inter- 

 ruption from the Gulf of St. Lawrence westward along the 

 northern base of the Notre Dame Mountains, a distance of 550 

 miles or more, the altitude of the highest at Gaspe being 210 

 feet, while as we approach the international boundary east of 

 Lake Champlain it is 865 feet. Another series extends along 

 the north side of the St. Lawrence and Ottawa rivers at approx- 

 imately the same altitude, reaching 900 feet north of the city 

 of Ottawa. Besides the regional upheaval indicated by the 

 shore lines observed on both sides of the valley, differential ver- 

 tical movements of a local character have taken place at inter- 

 vals along these strands since they were at sea level, or in a hori- 

 zontal attitude ; in some places there appears to have been a 

 greater uplift than in others, and such uplift seems occasionally 

 to have been followed by still more local downward movements. 

 On the south side of the valley and in the maritime districts 

 wherever the shore lines rest upon crystalline, or igneous rocks, 

 they were observed to be deformed to a greater extent than else- 

 where and raised above the average height. This singular and 



*This Journal, April, 1896, vol. i (4th series), pp. 302-308. 



f Annual report, (ieol. Surv. Can., vol. x, 1897 (new series), pp. 12-54 J. 



JThe term Pleistocene embraces the period beginning with the Post-Ter- 

 tiary and ending with the Champlain, or with the deposition of the Leda clay 

 and Saxicava sand. 



