500 J. A. DRESSER IGNEOUS ROCKS OF EASTERN QUEBEC 



Selwyn reached the conclusion that these folded ridges were anticlines, 

 not synclines, and held that the rocks composing them were older than 

 the Quebec group and consequently formed no part of it. The results 

 of the subsequent investigations of Doctor Ells substantiated this view. 



The first igneous rocks recognized in the Eastern townships were the 

 granites of Stanstead and Megantic, the syenitic rocks of Monteregian 

 hills, Brome and Shefford, and the Gabbro-diorites of Brompton, Orford, 

 and Ham. These were described at some length in the Geology of Can- 

 ada, 1863, and had been previously discussed by Hunt. 



Both Hunt and Logan regarded the serpentines as altered sediments 

 and correlated them stratigraphically with the dolomites, in view of their 

 magnesian contents. Doctor Selwyn seems to have been the first to point 

 out the probable origin of the serpentines, and also suggested that the 

 stratigraphic questions then under discussion were complicated by the 

 fact that some of the other highly metamorphosed rocks were in reality 

 disguised volcanics. A suite of specimens of doubtful rocks submitted 

 by him to Dr F. D. Adams* proved the serpentines to be altered igneous 

 rocks generally of the peridotite class, the so-called diorite to be diabases 

 and allied rocks, and some of the other highly altered rocks of the region 

 to be of sedimentary origin. 



The reexamination of the areal geology of the district which was 

 necessitated by this information was entrusted to Dr E. W. Ells, the 

 results of whose investigations appear in the annual reports of the years 

 1886, 1887, and 1894, and in the maps which accompany them. 



In these maps the crystalline belts of Sutton and of Stoke mountain 

 are represented as pre-Cambrian in age, and an area along the inter- 

 national boundary line is included in the same horizon. The sediments 

 intervening are assigned to the Cambrian and Cambro-Silurian, with 

 the exception of some very minor areas, which, as has been said, were 

 found to have been occupied with remnants of Devonian and possibly 

 of Silurian measures. The serpentines are included with the igneous 

 rocks and the occurrences of "diorite" are shown to be more numerous 

 than appeared in the earlier maps. The great body of the pre-Cambrian, 

 however, remained among the sedimentary rocks. 



Besides these investigations a few independent papers have been pub- 

 lished on the region. 



In 1876 Sir J. William Dawson discussed the mode of entombment of 

 certain fossils, referring especially to localities in the Eastern townships. 

 Some of the occurrences of fossils thus mentioned are of essential im- 

 portance to these investigations. 



* Annual Report, Geological Survey of Canada, 1880-1881-1882. 



