44: Dressar — ContribiiMon to the Geology of Quebec, 



As origiDally defined by Logan and Billings, the Quebec 

 Group embraced all the rocks of the Eastern Townships that 

 are essential to the present investigation, and all were then 

 regarded as of sedimentary origin. Subsequently, however, 

 Hunt, on stratigraphical grounds, and Selwyn on stratigraphi- 

 cal and lithological evidences, distinguished certain older 

 measures, which were referred by the latter to the early Cam- 

 brian and pre-Cambrian ages. The amplification of the views 

 has been fully carried out by Ells in the reports of the geo- 

 logical survey of Canada for the years 1886 and 1894. 



The only lithological changes embodied in these re- 

 ports are in the recognition of the eruptive origin of 

 the serpentines and the diorites, diabases, porphyrites 

 and granites generally associated with them. These had 

 been previously regarded as metamorphosed sediments. 

 The silicates of magnesia were correlated with its carbonates, 

 where dolomite occurred in the vicinity of the serpentine belt, 

 and even in 1886, Dr. Selwyn, who had been the first to 

 recognize the igneous origin of the serpentines, in a footnote 

 appended to Dr. Ell's report, maintains that the hornblende 

 granites are probably products of metamorphism in situ and 

 not true intrusives through the serpentine, as the latter writer 

 correctly considers them to be. 



In respect to age, the serpentines and certain of the elastics 

 were referred to the early Cambrian and the other eruptions to 

 middle or late Silurian time, while three belts of supposed 

 sedimentary rocks, running approximately parallel to the north- 

 easterly trend of the Appalachians were classed as pre-Cam- 

 brian. One of these appears for only a relatively short dis- 

 tance along the boundary line between the province of 

 Quebec and the State of Maine. The second crosses the St. 

 Francis river between the city of Sherbrooke and the vil- 

 lage of Lennoxville. This may be known as the Ascot or 

 Stoke Mountain belt, while the third, which crosses the St. 

 Francis river a little way north of the town of Richmond, 

 twenty- five miles northwest of the second, is generally designated 

 as the Sutton Mountain belt. The structure of these bands, 

 especially of the last mentioned, was long a crucial point in 

 the Quebec group controversy, they being interpreted as syn- 

 clines by the earlier investigators, and as anticlines by the 

 latter. 



Petrography. — Recent petrographical investigations by 

 the writer have, however, shown that both the second and 

 third of these pre- Cambrian belts consist largely, and in places 

 entirely, of altered volcanic rocks. These are so highly 

 altered and consequently so much disguised, that they have 



