THE TERRANES AND THEIR STRUCTURAL RELATIONS. 481 



at Point Levis. They occur in the following geographical succession, begin- 

 ning toward the north : 



1. Lauren tian or Archean. 



2. Trenton. 



3. Utica. 



4. Lorraine. 



5. Quebec (massif). 



6. Levis. 



7. Sillery. 



Between the Laurentian and Trenton terranes, numbers 1 and 2, there 

 occur an unconformity and an overlap, as seen at Lorette and Charlesbourg. 

 There we find the Trenton directly overlain by the Utica terrane, which is 

 in turn overlain by the Lorraine shales — in the district lying between Lorette 

 and Cote Sauvageau, Quebec city, — these three affording a regular ascending 

 series of sedimentary strata, whose characters are readily seen and recognized 

 throughout the region in question. Then follow toward the south the cal- 

 careo-bituminous rocks, indurated shales, compact limestones, and conglom- 

 erate bands which form the Quebec city massif, bounded on the north by a 

 thrust fault which brings them against the disturbed and twisted edges of the 

 Lorraine shales, and bounded on the south by the St. Lawrence river and 

 another fault which brings them in contact with the Sillery rocks toward the 

 southwest and with the Levis toward the southeast. On the southern side 

 of the St. Lawrence we find next the Levis shales, limestones and conglom- 

 erate bands coming in over the Sillery shales (red, green and gray) and 

 sandstones, with which they are folded and faulted many times. Taking 

 these terranes in their natural and present geographical order as above, they 

 may be described in detail. 



Description of the Terranes. 



The Laurentian or Archean. — Granites and gneisses, hornblendic and 

 micaceous rocks of usual occurrence in the lowest divisions of this system of 

 rocks, are met with at Montmorency falls underlying the Trenton limestone; 

 at Lorette falls, below the lowest beds of Trenton limestone there exposed ; 

 and also north of Charlesbourg village and quarries, presenting a series of 

 more or less elevated rounded bosses which, toward the west, north and east, 

 develop into hills and mountains of greater magnitude, whose southern limit 

 in the Quebec city region and vicinity seems to mark the line of an ancient 

 escarpment, which predicates the existence of an extensive dislocation in 

 the Archean crust and accounts for the peculiar absence of that series south 

 of this line. Mr. A. P. Low, of the Canadian Geological Survey, is now 

 engaged in mapping the geological features of the Archean area north of 



