276 W. H. Tivenhofel and W. H. Conine— The 



streams of the first group are probably in large part post- 

 Glacial. 



Concliisions as to the time of formation of the terraces. 

 — The terraces are shown along the valley walls of each 

 type of stream, but are not present on every stream, par- 

 ticularly those of youthful appearance. Many are known 

 to truncate Glacial and post-Glacial deposits, and beach 

 gravels have been seen on essentially every one of them. 

 Since the island was glaciated, the glaciers would have re- 

 moved the gravels, but might also have carried others 

 upward from the beach. Till is generally absent, but its 

 removal could have been most extensively and completely 

 accomplished by beach washing. The age of the lower 

 terraces is unquestionably determined. If the higher ter- 

 races be Tertiary, they would appear to be older than the 

 larger river valleys, but they are shown on the sides of 

 most of the latter, and are therefore subsequent. The 

 facts lead to the conclusion that all of the terraces are 

 post-Glacial. 



The question may be approached from another angle. 

 How long a time would be required to cut these terraces! 

 How long a time is required to cut a terrace a mile wide on 

 the rocks of the island! Wave erosion on Anticosti ap- 

 pears to be very rapid. The rock as an average is not 

 particularly strong, is much jointed, and there is much 

 frost wedging. At Heath Point, Mr. Christopher Hubert, 

 the light keeper, pointed out a road which had been moved 

 twice between 1909 and 1919, and the rock at that place, if 

 anything, is somewhat more resistant than the average. 

 The estimated width eroded in the ten years is 20 feet, or 

 a mile in a little over 2500 years, and at this rate, to cut 

 the present sea-level terrace at its greatest width would 

 have required about 7500 years. As the average width 

 of this terrace is not much more than a mile, it may be 

 assumed that about 3000 years were required for its devel- 

 opment. On the south side of the island the gradient of 

 the surface is gentle, and the surface low, so that in the 

 cutting of any one of the terraces the quantity of material 

 to be eroded and transported was not great, thus permit- 

 ting the terraces to develop to great width. On the north 

 side, erosion is just as easy, but the elevation above sea- 

 level is so much greater that a move of one foot inland 

 required the removal of from five to forty times as much 

 material as is the case for a movement inland of the same 



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