32 



In the Geology of Canada, 1863, Logan [8] described 

 the Quebec group in great detail, tracing it from the well 

 known exposures at Point Levis both east and southwest, 

 where it was supposed to have been altered into a complex 

 series of crystallines. He still believed the Sillery to 

 be above the Levis, "provided the series was not inverted." 

 He gives a map showing the structure at Point Levis, 

 and divides the Levis into 17 zones, with a total thickness 

 of 5,025 feet (1530 m.). The thickness of the Sillery 

 was estimated at 2,000 feet (600 m.). 



A comparison of the sections in Canada and Newfound- 

 land led Billings [9] in 1865 to the opinion that the shales 

 at Point Levis were at least 2,000 feet (600 m.) above 

 the Calciferous (Beekmantown). 



Lapworth, [10] in 1886, identified a number of collections 

 of graptolites made by T. C. Weston, and correlated the 

 fauna found at Point Levis with that found in the Arenig 

 of England. He also studied the graptolite fauna which 

 had been collected in the City of Quebec, and stated 

 that their age was probably Black River or Lower Trenton. 

 The above correlations have since that time been univer- 

 sally adopted. 



Ells, [11] in 1888, gave an excellent summary of all work 

 up to that time, a detailed description of the various 

 formations in this region, and many new lists of fossils, 

 the latter determined by H. M. Ami. 



A POSSIBLE EXPLANATION OF THE GEOLOGICAL 

 STRUCTURE. 



The prevailing strike of all the sedimentary rocks in this 

 area being NE-SW, and the dips generally to the SE, it 

 was at first supposed that the strata formed a regular 

 ascending series from the gneiss at Montmorency to the 

 supposed Upper Silurian red shales of the Sillery south of 

 the St. Lawrence. The discovery of fossils, however, 

 showed this view to be incorrect, and each subsequent 

 collection of fossils has shown the structure to be more com- 

 plicated than it had previously appeared. 



