[ELLS | GEOLOGY OF THE OTTAWA PALÆOZOIC BASIN 119 
fact that the fossiliferous strata of this period have been involved in a 
great series of foldings and fractures at several widely separated points. 
lt is presumable therefore that the main lines of disturbance, west of 
Rigaud mountain, may belong to the same period. 
The fact has also been conclusively established that in connection 
with the great area of the crystalline rocks, north and south of the 
Ottawa river, masses of intrusive rocks, consisting of granites, gabbros 
and diabases, are to be found. Some of these are evidently of later 
date than the Calciferous limestone with which, they are sometimes 
associated and which at certain points have been altered by these in- 
trusive masses; while at one point at least on the upper Ottawa, the 
Black River limestones at the contact with the crystalline rocks are 
broken up and also altered to some extent, and are inclined at an angle 
of nearly fifty degrees in close proximity to masses of intrusive granite 
associated with the gneiss and crystalline limestones. | 
The fact that some of the most pronounced displacements in the 
vicinity of Ottawa city and in the area to the west, occur where granitic 
masses are conspicuous, may have a bearing on this question. In con- 
nection with the heavy faults in Huntley and Fitzroy it has already 
been shown that these sometimes follow the outlines of the ridges of 
crystalline rocks with which masses of granite and diorite are associated. 
The same relations are seen in the township of Hull. In the case of the 
large mass of granite seen near Grenville, which is apparently one of 
the most recent of these, since it cuts the diabase dykes which traverse 
the rocks of the Grenville series, it is quite possible that the age of such 
masses is not far removed from that of the eruptive hills nearer Mon- 
treal. It is to be regretted that, owing to the-prevalence of the drift 
in this area, more precise contacts of these granites with the rocks of 
the Paleozoic series cannot be readily observed. 
The great movement which produced the extensive fractures in the 
district east of Montreal, among which may be placed the great St. 
Lawrence and Champlain fault, is comparatively recent. It was 
evidently from the south-east, and the amount of displacement in this 
area aggregated several thousands of feet. The denudation over this 
part of the province must have been enormous, since in most cases the 
newer formations have been almost entirely removed and are now re- 
presented by solitary patches, sometimes of very limited extent. In 
the upper Ottawa basin also a similar denudation must have occurred, 
since limited areas of the fossiliferous sediments, some of which are as 
recent as the age of the Niagara formation, are now met with, resting 
on the crystalline rocks at widely, separated points. 
