268 W. H. TivenJiofel and W. H. Conine— The 



Aet. XYII. — The Post-Glacial Terraces of Anticosti 

 Island; by W. H. Twenhofel and W. H. Conine. 



Introduction. 



Detailed description of the terraces. 



The sea-level terrace. 



The terraces above sea -level. 

 Origin of the terraces. 

 Time of origin of the terraces. 



Glaciation of the island. 



Champlain submergence. 



Deposits of post-Champlain time. 



Age of the river valleys. 



Conclusions as to time of origin. 

 Correlation with terraces elsewhere. 



Introduction. 



There are probably no more impressive features in the 

 physiography of Anticosti Island than its terraces. Like 

 stairways for giants, they begin at the level of the sea — 

 possibly below sea-level — and continue into the interior as 

 far as the eye is able to follow. The highest measured 

 exceeds 400 feet. The cliffs or steep slopes which front 

 them vary greatly both in height and in extent. In places 

 a terrace may have a width of a mile or more ; in other 

 places it narrows to disappearance, with its cliif or front 

 slope merging with the cliff or front slope of one of those 

 above. The places of greatest width are about the inden- 

 tations of the coast; the places of least width are on the 

 salients. 



Anticosti Island is a cuesta with the escarpment facing 

 north, the dip slope facing to the south. The northern 

 channel occupies the inner lowland. The trend of the 

 island is not parallel to the structure nor is the strike of 

 the strata identical with the trend of the island. Pro- 

 gressively younger strata are met in proceeding eastward 

 along the north side, progressively older strata in going 

 westward and eastward from Southwest Point along the 

 south side. 



The asymmetry of the island's surface with respect to 

 its north and south slopes is reflected in its terraces. 

 On the south side, some of them are several miles ^\T.de, 

 and to reach the summit of the highest, it is necessary, in 

 most places, to go somewhere near the middle of the 

 island. On the north side, the highest observed terrace 

 may be reached in many places within a couple of miles 



