[amr] GEOLOGY OF SOME CITIES IN EASTERN CANADA 139 
The Black River, Trenton, Utica and Lorraine formations as de- 
veloped about Quebec, form an ascending series of rock formations which 
are found to overlie unconformably, and come in contact with, the 
Laurentian crystalline rocks to the west of the Great Fault. 
One of the most prominent features about the geology of Quebec 
is the occurrence of the great St. Lawrence-Champlain or Appalachian 
Fault, which brings the fossiliferous beds of the Quebec group in direct 
. ecntact and close proximity to other Ordovician formations. This 
great fault or dislocation must be pre-Sillery at least and was un- 
doubtedly a conspicuous factor in marking the limit of the different 
areas in which the conditions of sedimentation differed widely, at one 
and the same time, to the north-west and to the south-east. It has 
often been a question in the mind of the writer whether the peculiar de- 
velopment of the three formations comprising the Quebec group in this 
locality, viz: the Sillery, Levis, and Quebec, was not synchronous with 
that of the Potsdam, Calciferous and Chazy formations met with in 
and about Montreal, Ottawa and other typical localities in the undis- 
turbed regions of the interior Continental Paleozoic Plateau ; neverthe- 
less there is evidence at hand to show the Lower Trenton age of some of 
the strata of the Quebec formation in Quebec city. 
The absence of the typical Potsdam Calciferous and typical Chazy 
formations about Quebec city, must be due to the peculiar conditions of 
deposition at the time. There is little doubt, however, that the general 
conditions under which the Sillery, Levis and Quebec formations were 
deposited remained practically the same during that portion of the 
Ordovician and upper Cambrian, and continued on and prevailed to the 
south-east of the great break later on through the Silurian, Devonian 
and even Carboniferous times in which oceanic Atlantic currents existed 
which gave rise to the various sedimentary formations peculiar to the 
Eastern Acadian or Atlantic Province. 
Overlying the Ordovician formations and forming the cuttivated 
soil of the fertile valley of the St. Lawrence and its tributaries about 
Quebec, we find a regular succession of Pleistocene formations to be 
prevalent. 
THE LAURENTIAN OR ARCHÆAN. 
The granitoid gneisses and other crystalline rocks referable to this 
portion of the great protaxis, have been studied to some extent in de- 
tail by Mr. A. P. Low, of the Geological Survey, during his field explora- 
tions in this district and also microscopically by Mr. W. F. Ferrier. 
The general topography of the Archean rocks is practically the 
same as is met with everywhere, with this additional feature that some 
