27 



between Quebec and Levis, but is seen along the northern 

 side of Orleans island, where the Levis formation is thrust 

 upon the Quebec city formation. The second fault passes 

 from above Cape Rouge on the St. Lawrence along the 

 northern side of the ridge on which the city is situated 

 and thence along the valley of the St. Charles into the 

 St. Lawrence, where it passes between Orleans island and 

 the north shore at Montmorency. By this fault the 

 Quebec City formation is thrust over the Sillery and 

 Lorraine. The third fault is well shown at Montmorency, 

 where, by a drop of about 600 feet (180 m.) the Lorraine 

 is brought down to abut against the Pre-Cambrian. 



The main structure and the faults are shown in the 

 accompanying generalized section across the valley. 



In the absence of any detailed knowledge, the amount 

 of lateral movement involved in the thrusts can only be 

 conjectured. It must be very great however, for the 

 Sillery, Levis and Quebec City formations do not belong 

 to the same province of deposition as the Trenton, Utica, 

 and Lorraine. In the region north of the Si . Lawrence the 

 Trenton rests upon the Pre-Cambrian with sponges and 

 corals adhering to the gneiss in the position in which they 

 grew, thus showing that the contact is not due to a fault. 

 Yet, only a mile away, on the Island of Orleans, is a great 

 thickness of older (Lower Ordovician) rocks. Logan 

 explained this by assuming a very great steepness for the 

 shore line here, so that the gneiss of Montmorency was 

 not submerged till Trenton time, but now that we know 

 that both the Quebec City formation and the limestone 

 at Montmorency are of Trenton age, though with hardly 

 a fossil in common, it becomes impossible to accept this 

 explanation. In New York State, the strata containing the 

 same fauna as the Quebec City rocks, lie nearly 50 miles 

 (80 km.) east of the nearest outcrop of strata containing 

 the typical Trenton fauna, but the thrust need not 

 necessarily have been so much as that. 



The following formations, amongst others, occur in 

 the vicinity of Levis, Quebec, and Montmorency. 



