16 



large and small, detached areas which are surrounded and 

 penetrated by Carboniferous measures. 



PHYSIOGRAPHY. 

 (J. W. GOLDTHWAIT.) 



Eastern Quebec and the Maritime Provinces lie at 

 the northeastern end of the Appalachian Mountain region 

 of eastern United States and Canada. This region, 

 although not generally mountainous at the present time, 

 possesses a complex and crumpled rock structure which 

 can only have been produced by diastrophism. Since 

 Cambrian, Ordovician, Silurian, and Devonian sediments 

 are all involved in the close folds, and partake of the 

 regional metamorphism that characterizes the province, 

 it is evident that the region was very mountainous in 

 Palaeozoic time. While the Mesozoic rocks have 

 suffered much less deformation, they too, show that as 

 late as the end of the Jurassic period diastrophism was 

 taking place on a large scale. It is probable then, that 

 at the beginning of the Cretaceous period this whole 

 region was occupied by lofty mountain chains. During 

 the closing part of the Mesozoic, however, subaerial 

 denudation appears to have held sway without interrup- 

 tion from diastrophism. The mountains were slowly 

 but surely reduced to a plain of low relief, or "peneplain". 

 Remnants of this great baselevelled surface of the Cre- 

 taceous can be found along the Appalachian system all 

 the way from New Brunswick to Alabama. Locally, 

 in districts remote from the coast, and where stronger 

 rock structures appeared just above the Cretaceous base- 

 level, the reduction of the surface was incomplete, and 

 many residual mountains or "monadnocks" were left. 

 On the whole, however, the baselevelling was very thorough, 

 planing away the harder rocks as well as the weaker. 



This almost complete cycle of denudation was brought 

 to a close at about the beginning of the Tertiary by regional 

 uplifts of continental extent. All along the Appalachian 

 province, in United States and Canada, the Cretaceous 

 peneplain was raised, with more or less warping converting 

 the lowland into an upland. The uplift seems everywhere 

 to have been greatest in the interior and least near the 

 coast. By it, the seaward flowing rivers were revived, 



