Sea- Cliff of the Zotoer Saint Laiorence. 293 



by a slow elevation of 20 feet. A brief description of the f nil 

 series of Chaniplain beaches will first be given, in order to 

 emphasize the unique character of the twenty-foot strand. 

 Two working hypotheses to explain the peculiar strength of this 

 terrace will then be presented; and a number of reasons will 

 be given for the view that the post-glacial movements of the 

 coast, in southern Quebec, have consisted in an uplift, a 

 subsidence, and a second uplift. 



The Raised Beaches op the Lower Saint Lawrence. 



The Higher Beaches. 



The elevated shorelines along the south side of the Saint 

 Lawrence, below the city of Quebec, are as a rule very weak 

 in topographic expression. This Weakness is especially notice- 

 able near the upper limit of submergence. In most places the 

 utmost care is required to select the critical horizontal line which 

 marks the highest stand of the sea since the ice age. During 

 the course of the field season of 1910, this upper limit of sub- 

 mergence was measured at fifteen localities on the south shore 

 between Matane and Quebec. At many of these localities the 

 highest beach is hardly more than an upper limit to stratified 

 sands. Even where it possesses definite form, such as a low 

 beach ridge or a hooked spit, this feature cannot be traced far 

 before it disappears more or less completely against a hillside 

 where the slope or the structure of the ground was originally 

 unfavorable to the development of a distinct beach. 



At not a single place, during the season of 1910, was the 

 higbest shoreline found to consist of a sea-cliff and wave-cut 

 terrace. This was a source of surprise for two reasons : because 

 of the long-standing use of the word " terrace " in the literature 

 on the beaches of this region ; and because there are strongly- 

 cliffed shorelines around the borders of the extinct lakes Algon- 

 quin and Nipissing, where one might expect less vigorous wave 

 action and less definite shore topography than along the borders 

 of a great estuary like the Saint Lawrence. 



The inference to be drawn from the weakness of the highest 

 marine beach is either that the upwarping began almost imme- 

 diately after the withdrawal of the ice and the opening of the 

 estuary to the sea, or that it began while the ice still lingered 

 in the region, and was alread}' in progress when the estuary 

 was opened. 



Traces of wave work along the south coast of the Saint 

 Lawrence were found at all altitudes below the upper limit of 

 submergence. Contrary to expectation, again, there proved to 

 be no shoreline below the highest one, with the exception of 

 the twenty-foot strand, which possesses enough individuality 



