ROCK DIVISIONS ON THE ST. LAWRENCE. 401 



Cambrian ; but in the section south of Levis these are in turn succeeded by 

 the great series of red aud green slates of the Sillery, which, thrown into 

 complicated folds, occupy a surface breadth of some miles between the river 

 and the interior ridge. All the formations here developed have a very uni- 

 form strike, following for the most part the trend of the St. Lawrence. In 

 the course of our examinations, many sections were made directly across 

 the measures, the structure in nearly every case proving to be the same and 

 sustaining the views already expressed in regard to the southeastern area. 



What we now consider the lowest portion of the unaltered Quebec group, 

 as developed in the vicinity of Quebec and Levis and for some miles south 

 of the latter place, is seen in a sectiou on the north side of the St. Lawrence, 

 beginning about ten miles above the city of Quebec. From this point, which 

 marks the line of fault bringing into contact the rocks of the Hudson River 

 formation, what appears to be a regularly ascending sequence of beds is ob- 

 served till we reach Pte. a Pizeau, about two miles above Quebec, in the dis- 

 trict of Sillery. This section we have divided into four parts, and may briefly 

 summarize as follows : 



Division 1. Consists largely of quartzose sandstone interstratified with 

 black and gray shales, and contains at one point a band of fine conglomerate 

 made up of small pebbles of limestone and quartz in a highly siliceous paste. 

 No fossils have yet been found. 



Division 2. Comprises green, black, and gray shales or slates, with occa- 

 sional bands of hard sandstone. Thin beds of purple-tinted slates occur in 

 the upper portion. Many of the slaty surfaces are covered with worm trails, 

 styled fucoids in the earlier reports of the Geological Survey. These beds 

 are also well seen on the hill in the rear of Cape Rouge village. 



Division 3. Comprises mostly reddish and green shales without sandstones, 

 or with the latter in but small quantity. 



Division 4. Consists of sandstones largely developed, with partings (often 

 of considerable thickness) of red, gray, green, and black shale. The sand- 

 stones are local, the areas thinning out in either direction ; and the green 

 shales, which are associated with the red, contain Obolella pretiosa. These 

 are the typical Sillery sandstones described in the Geology of Canada, 1863. 



From Pte. a Pizeau the rocks of division 4 apparently strike diagonally 

 across the St. Lawrence and appear on the south side of the river at Point 

 Levis, where their characteristic red color serves well to indicate them. At 

 Levis these are succeeded by the rocks of division 5, which consist of 

 blackish green and gray shales with dolomitic limestone and limestone con- 

 glomerate. The black shales contain graptolites, and the conglomerates are 

 fossiliferous both in the paste and in the pebbles. These make up the bulk 



LXI— Bull. Geol. Soc. Am., Vol. 1, 1889. 



