TRANSACTIONS OF SECTION C. '641 



These newer gneisses and limestones which have been staled by Logan the 

 * Grenville Series ' are, without doubt, tor the most part of sedimentary origin, 

 though they are invaded in all directions by masses of granite, greenstone, and 

 other I'orms of igneous rock. As for the Fundamental Gneiss, also once supposed 

 to l)e largely of sedimentary origin, it has been very conclusively demonstrated, 

 chiefly through the agency of the microscope, that this is for the most part at least 

 an altered igneous rock, and that the supposed bedding planes owe their existence 

 to other causes than those of sedimentation. 



The original upper Laurentian division, which included the great area of the 

 Anorlhosite rocks, also supposed at one time to represent altered sedimentary 

 deposits, has been removed from the position it once occupied, since it has been 

 proved, both by the evidence in the field and in the laboratory, to be of igneous 

 origin and subsequent to the deposition of the limestone and quartzite series with 

 which it is associated, so that the Grenville Series, according to the earlier view as 

 to the succession of strata, may now be taken to represent the upper portion of the 

 liaurentian system. 



It may also be assumed to represent the lowest division of the clastic or sedi- 

 mentary rocks in Canada. The relations of these to the rocks which have been 

 styled the ' Hastings Series ' in Ontario are such that they may, in part at least, 

 be regarded as portions of the same series which have been described in different 

 portions of the field under different names ; but whether these be regarded as 

 belonging to the Laurentian or Huronian systems is of small moment so long as 

 their true relationship to each other and to the underlying Fundamental Gneiss is 

 clearly understood. 



To the east of the St. Lawrence the old dispute aslo the age of the fossiliferous 

 rocks near the city of Quebec, as well as of their relations to the crystalline schists 

 of the mountain area in the interior of the province, may now be considered as 

 satisfactorily settled. The former hypothesis by which the crystalline schists were 

 regarded as the equivalents, in point of time, of the fossiliferous sediments of the 

 St. Lawrence Valley has been clearly shown to be unfounded, and the schists of 

 the Sutton Mountain area are now assigned to the Huronian system, or are at 

 least beneath the lowest Cambrian of the district. The relative position of the 

 several divisions of the fossiliferous Quebec group has also been ascertained, and 

 it is now established that the Sillery division is situated stratigraphically beneath 

 the L(5vis, instead of being, as was at one time supposed, above it. As regards the 

 age of the several divisions of the Quebec group (fossiliferous) it may be said that 

 the L^vis is the apparent equivalent of the Calciterous formation, and that in its 

 upper portion it approaches the Chazy ; while the upper portion of the Sillery is 

 the apparent equivalent of the Potsdam Sandstone formation. Between the Upper 

 Sillery and the great mass of the rocks which have been referred to this division, 

 there is a fault of considerable magnitude, so that the lower portion of the Sillery 

 presumably includea rocks which have been elsewhere classed as Cambrian, and 

 these may extend as low as the Paradoxides zone or division of that system. 



The areas of black slate and limestone, which, in the General Report for 1863, 

 were regarded as beneath the crystalline schists, and referable to the Potsdam 

 formation, have been determined, on the evidence of the contained fossils, to be 

 much newer, and to be in fact the equivalents of the lower portion of the Trenton 

 formation ; and to this horizon may also now be assigned the greater portion of 

 the strata in the city of Quebec. Here, however, there are a number of anti- 

 clinal folds, and the presence of certain fossils, similar to those obtained from 

 the Levis beds, indicates that along some of these folds beds of that horizon may 

 be found. The same age may be assigned to the great extension of the black slates 

 find limestones which occur at intervals along the south shore of the St. Lawrence, 

 nearly to the extremity of the Gasp6 Peninsula, and which appear to dip beneath 

 the strata of the Sillery formation at many points. 



In regard to the use of the term Potsdam a distinction must now be made be- 

 tween the Potsdam formation and the Potsdam Sandstone. The latter has been 

 clearly proved in Canada to be the lower portion of the Calciferous formation, and 

 is not separable from it, while there is a manifest break between this and the 



1897. T T 



