J. A. Dresser— Study in Metamorphic Hocks. 67 



Art. Y. — A Study in the Metamorphic Rocks of the St. 

 Francis Valley, Quebec • by John A. Dresser. 



The Quebec group as originally defined embraced several com- 

 paratively narrow belts running parallel to the folding of the 

 Appalachians throughout the extent of that system in Canada.* 

 They were found to consist of much altered strata of Cambro- 

 Silurian age, which had been deposited under peculiar condi- 

 tions such as to strongly distinguish them from normally depos- 

 ited strata of the same age. In structure they were thought to 

 generally form synclinal folds, often highly distorted and 

 overturned. All lay to the east of the dislocation run- 

 ning from the northern end of Lake Champlain to the St. 

 Lawrence river in the vicinity of Quebec city, which is known 

 as the Champlain and St. Lawrence fault. 



It was subsequently ascertainedf that within the Quebec 

 Group thus defined there had also been included certain older 

 measures belonging to the Cambrian and Precambrian systems, 

 and also frequent and extensive masses of ancient and highly 

 altered rock of volcanic origin,:}; whose igneous character 

 had not been previously recognized. Accordingly, in the 

 re- examination more recently made by the Geological Survey of 

 Canada,^ these rocks along with certain of the associated vol- 

 canics have been separated from the Quebec Group, but the 

 progress of geological investigation has not yet admitted of a 

 very detailed subdivision. 



The most extensive of the older belts thus brought to light 

 is that which comprises the Sutton Mountain anticline, fig. 1, the 

 course of which, in common with the other principal axes of 

 the Appalachians is a northeast-southwesterly one. Near the 

 St. Francis river, which crosses it about at right angles, it is 

 rather less than six miles wide, including a small band of 

 Trenton whose position within the older measures has been 

 hitherto explained as " due to an intricate system of folding 

 and faults."| 



A section across the Sutton Mountain series and the included 



* " Geology of Canada," 1863, pp. 225-297, Sir W. E. Logan. 



\ " The Quebec Group in Geology," Transactions of the Eoyal Society of 

 Canada, vol. i, 1882, Dr. A. R. C. Selwyn. 



% ' ' Notes on the Microscopic Structure of some Rocks of the Quebec 

 Group," Report Geological Survey of Canada, 1880-1-2. Dr. F. D. Adams, 

 "The Quebec Group," Appendix A to Harrington's " Life of Sir W. E. 

 Logan," by Sir J. W. Dawson, 1883. 



§ Annual Reports Geological Survey of Canada, 1880-1-2, and 1887-8, Dr. 

 A. R. C. Selwyn ; 1886, 1887-8 and 1894, Dr. R. W. Ells. 



|| Ann. Report Geol. Survey, 1886, p. 18 J. 



