[WILSON] PALEOZOIC TO THE PRE-CAAIBRIAN 21 



Alumette Island, and the Kingston district on the west and are absent 

 outside this region not only on the east and west but in the outliers of 

 Palaeozoic occurring far within the Laurentian highlands on Lake 

 Timiskaming^ and on Lake St. John.^ 



It may be concluded, therefore, that the early Palaeozoic forma- 

 tions occurring in the lower St. Lawrence basin were deposited in a 

 widely extended depression which had a depth equal to the thickness 

 of these formations or from 600 to over 1,000 feet throughout nearly 

 its entire extent. 



It has been previously noted that throughout the greater part of 

 the region adjoining the southern border of the Laurentian highlands 

 the Palaeozoic formations dip to the southward away from the Pre- 

 Cambrian upland and in consequence outcrop in successive parallel 

 belts trending approximately parallel to the margin of the plateau, 

 and, since these formations were presumably laid down originally in 

 horizontal position, they have evidently been down warped relatively 

 to the pre-Cambrian highlands since they were deposited. Thus in 

 the region adjoining the southern border of the Laurentian highlands, 

 between Montreal and Quebec and in central Ontario, the Palaeozoic 

 formations have been depressed from several hundred to several 

 thousand feet with respect to the adjoining highlands, and similarly in 

 the region which lies between the Laurentian highlands and the 

 Adirondack mountains, of New York State, despite the fact that the 

 relationships in this locality have been somewhat obscured by faulting, 

 the distribution of the Palaeozoic formations indicates clearly that 

 these have been folded into a broad syncline. As a consequence of 

 this folding the top of the Trenton formation in southeastern Ontario 

 stands approximately at the same elevation as the base of the Potsdam 

 outcropping along the northern border of the Adirondack mountains 

 in New York State, so that the Palaeozoic strata in Ontario with 

 respect to those occurring a few miles to the southward in New York 

 State have been depressed over 1,200 feet.^ 



So far as known, nearly all the important faults that intersect 

 the Palaeozoic strata outcropping in the northern part of the lower 

 Ottawa and St. Lawrence valleys are confined to a belt of territory 

 lying along the Ottawa river between a point a few miles west of 

 Ottawa and Montreal. These faults, as shown in the figure on page 

 16, generally trend in an east-west or northwest direction and have 



» Williams, M. Y., Mus. Bull., No. 17, Geol. Surv., Dept. of Mines, Can., 1915. 

 » Dresser, J. A., Mem. 92, Geol. Surv., Dept. of Mines, Can., 1916, pp. 29-35. 

 Hume O.S. Sum. Rep., Geol. Surv., Dept. of Mines, Can. 1916, pp. 188-192. 

 *See map accompanying N.Y. State Mus. Bull. No. 191, by H. P. Gushing. 



