﻿ProUcms in Quebec Geology. 501 



a large area has clearly shown that in their original form 

 the greater part of these are igneous rocks and that 

 in point of time they are among the newest of our rock 

 formations. Thus while they are often found closely 

 associated with strata that extend downward as low 

 as the pre- Cambrian, they are also seen in connection 

 with Silurian and Devonian strata and have altered these 

 to a very considerable extent. They may, in part, 

 therefore, be considered as newer than Upper Silurian, or 

 in fact than the lower part of the Devonian, since 

 the fossiliferous strata of these formations have been 

 altered by their action. 



The recent age of these rock masses will probably apply 

 to the greater portion of the igneous rocks lying to 

 the east side of the Sutton Mountain anticlinal which 

 extends from the Vermont boundary for at least 150 

 miles to the north-east. It also applies presumably to a 

 number of isolated mountains which rise from the 

 generally level country of the St. Lawrence plain. 



There are, however, quite extensive areas of altered 

 igneous rocks in connection with the crystalline schists of 

 the mountain range. Some of these undoubtedly underlie 

 the lowest Cambrian strata of quartzites and slates, 

 and must, therefore, be older than these. The serpentines 

 are, however, closely associated with the diabase moun- 

 tains east of the anticlinal, and, therefore, belong to 

 the newer period of igneous action. They are apparently 

 altered diabase or olivine rocks. These diabase mountains 

 sometimes form areas of considerable extent and are 

 always conspicuous features in the landscape. 



The igneous rocks of the Gaspe peninsula are of two 

 kinds. Some of the masses are undoubtedly comparatively 

 new, while others, as in the case of the Shick-Shock 

 range, consist of hornblende, epidote, chlorite and serpen- 

 tine, portions of which are apparently older than the 

 slates of the Cambrian system, which occur along their 

 northern flank. 



