25 



Kilometres ^e southeastern portion of the plain is 



occupied by closely folded and faulted measures 

 of Ordovician and, possibly, Cambrian age. 

 These disturbed measures are lithologically and 

 faunally unlike the flat-lying, in part, at least, 

 contemporaneous strata of the northwestern 

 portion of the region. They belong to the 

 geological province which includes the elevated 

 bordering uplands on the southeast underlain 

 by strata ranging in age from Pre-Cambrian to 

 Devonian and which are accompanied by 

 igneous rocks of both volcanic and plutonic 

 types. 



The boundary between the gently dipping 

 Ordovician on the northwest and the much 

 disturbed, in part metamorphosed, strata on 

 the southeast, though it traverses the length of 

 the lowlands, is not marked at the surface by 

 any topographical feature. The level, plain- 

 like surface extends uninterruptedly across the 

 boundary which is formed by a zone of faulting, 

 known as the St. Lawrence and Champlain 

 fault. This zone of faulting extends in a nearly 

 straight course northeast from the foot of Lake 

 Champlain to the St. Lawrence river a few 

 miles above Quebec. From there it continues 

 northeastward down the channel of the St. 

 Lawrence. This fault or zone of faulting, first 

 recognized by Sir W. E. Logan, has a length of, 



162.8 m. presumably, about 900 miles (1450 km.). 



262 km. Levis. (Opposite Quebec city). 



QUEBEC AND VICINITY. 



(Percy E. Raymond.) 



INTRODUCTION. 



The beetling cliffs which make Quebec the "Gibraltar 

 of America" have been a puzzle to geologists since the 

 earliest days of the science in America. The "Quebec 



*See Map, -Quebec and Vicimty. 



