Goldthwait — Twenty-Foot Terrace and Sea-Cliff. 291 



Art. XXXV.— The Twenty-Foot Terrace and Sea-Cliff of the 

 Lower Saint Lawrence ;* by James Walter Goldthwait. 



Contents : 



Page 



Introduction - 291 



The raised beaches of the Lower Saint Lawrence 293 



The higher beaches 293 



The twenty-foot terrace and sea-cliff 294 



The significance of the Micmac shoreline 305 



The place of a cliffed coast in shoreline morphology.. 305 

 Hypothesis of an interval of stability between two 



uplifts ". 307 



Hypothesis of an interval of coastal subsidence be- 

 tween two uplifts 309 



Independent evidence of subsidence 309 



Post-glacial movements in Scandinavia 311 



Conclusion 317 



Introduction. 



Among the raised beaches which border the Saint Lawrence 

 estuary in southern Quebec, one is so conspicuous and so 

 peculiar that it deserves especial attention. It is a strongly 

 cut sea-cliff and terrace which stands hardly 20 feet above the 

 present sea level. Although this is a much more maturely 

 developed shoreline than the higher beaches which mark the 

 work of the "Cham plain" sea, on the one hand, or the faint 

 beach which marks the modern high tide level, on the other, 

 the twenty -foot terrace and cliff seem to have excited little 

 interest. This is probably due in large measure to the fact 

 that the few investigators of the Champlain deposits who have 

 worked in this field have been so intent upon tracing the high- 

 est level of marine submergence that they have passed by the 

 lower strand as a feature of comparatively little significance. 

 The only recognition of the twenty-foot terrace which the 

 present writer has found, in the literature on the surface 

 geology of this region, appears in Sir William Logan's " Geol- 

 ogy."f It is there stated, presumably on the authority of Sir 

 William Dawson, who collaborated in the writing of the 

 chapter on surface geology, that 



"At Riviere dn Loup, the shells of Mya and Tell in a are found 

 imbedded in the sand and disintegrated shale of an ancient beach 

 only a few feet above the present sea level. Similar beaches, 

 which seldom attain more than fifteen feet above high-water mark, 



* Published by permission of the Director of the Geological Survey of 

 Canada. 



f Geology of Canada. Eeport of progress of the Geological Survey of 

 Canada, from its commencement to 1863. Montreal, 1863, p. 921. 



