146 ROYAL SOCIETY OF CANADA 



eighty feet. The shaly beds of the Chazy do not appear in this direction, 

 but the upper part of the plateau is occupied by the lower portion of the 

 Trenton proper. 



A somewhat extensive and important outlier is that found on the 

 Bonnechère and extending on both sides of that stream for several miles. 



To the east of Lake Doré, a ridge of a hundred feet or so in height is 

 thickly strewn with large blocks of Black Eiver limestone and with 

 boulders of Laurentian gneiss, the former holding characteristic fossils of 

 the formation. Well defined ledges, however, ravel}' appear, though 

 they are found at several points, rendering it proljable that they underlie 

 the area over a very considei-able extent. These massive blocks of the 

 Black Eiver limestone form a ])eculiar feature, not only here but at 

 several widely separated points and show that the Black Eiver formation 

 has had a very considerable development, being probably spread in a 

 regular sheet at about the same elevation over long distances, throughout 

 that part of the Ottawa basin above the Chats Falls in the vicinity of 

 Arnprior, the beds near which place would seem to mark a second stage 

 of elevation in the deposition of this formation. 



In the bed of the Bonnechère Eiver near the village of Douglas, well 

 defined ledges of the Chazy shales and sandstones are seen which dip at 

 angles of 5° to 20° and these pass upward into the characteristic Chazy 

 limestone which at the summit of the ridges to the north and south 

 graduates into the Black Eiver formation. What are regarded as Trenton 

 beds are stated to occur at Jessup's Eapids about seven miles west of 

 Douglas and not ftir below the town of I'^ganville ; but as the lower 

 (3hazv occupies the bed of the stream at that place, dislocations must 

 occur which have broken the regular succession of strata. The beds of 

 the Black Eiver are well exposed at this place, both along the stream and 

 on the hills to the south, the thickness of the formation here being 

 apparently not far from one hundred feet. Sections of the formations at 

 these places on the Bonnechère were published by Murray in 1854.' 



The elevation of the Eiver Bonnechère at Douglas, is given by Murray 

 at 383 feet The area along the stream is separated to the north by a 

 ridge of crystalline limestone and gneiss, on which Douglas village is 

 built, from a more extensive area which occupies a very considerable 

 portion of the townships of Bi'omley and Wilberforce, and extends from 

 the eastern side of Doré Lake for some fifteen miles in a southeast direction 

 with an average breadth of from four to five miles. The upper beds of 

 this outlier clearly belong to the Trenton formation, while to the south 

 of the Bonnechère, Black Eiver beds have a breadth of over one mile and 

 extend for several miles eastward in a ridge along tiie south side of the 

 stream. The two areas presumably connect in the fiat-lying country to 

 the east of Douglas. To the south of Egan ville also an extension of the 



• Report of Progress, 1853-50, pp. 94-9S. 



