SECTION IV., 1900. [ 99 ] Trans. R.S. C. 
IV.—The Physical Features and Geology of the Palæozoic Basin, between 
the Lower Ottawa and St. Lawrence Rivers. 
By R. W. Ezzs, LL.D. 
(Read May 29, 1900.) 
In a paper read before this Society in 1894, the distribution of the 
principal Paleozoic outliers in the Ottawa basin was given. Since that 
date, however, a large amount of field work has been done by the officers 
of the Geological Survey in the district, not only along the Ottawa river 
itself, but in the country between the lower Ottawa and the St. Law- 
rence rivers, and many additional facts, relating to the structure of 
the fossiliferous rocks in the area, have been obtained. Some of these 
new facts are of interest, as relating to certain points of structure, more 
particularly as regards the presence of faults and anticlines which affect 
the generally horizontal formations, which have not heretofore been 
pointed out. They also elucidate some features in connection with 
economic questions pertaining to portions of the area, more especially 
with reference to the probability of the occurrence of natural gas and 
oil, concerning which considerable inquiry has lately arisen. 
In the area between the lower Ottawa and the St. Lawrence rivers, 
there is a widespread development of the lower Paleozoic formations. 
These range upward from the base of the Potsdam sandstone, which is 
seen at a number of points resting upon the denuded surface of the 
crystalline rocks of the Archean system, to the Medina shales, which 
here represent the lowest member of the Silurian proper. While these 
are all affected by low undulations, they lie generally in the form of a 
broad synclinal basin, the northern margin of which is seen along the 
Ottawa river, where it is bounded by the great area of the crystalline 
rocks which cross that stream from the south about thirty-five miles 
west of Ottawa city. 
The western margin of this basin is also defined by crystalline rocks 
such as gneiss, limestone and certain granites, which belong to the 
Hastings series. The eastern margin of these rocks extends in a some- 
what irregular outline from the vicinity of Arnprior to the Rideau Lakes 
and thence to the St. Lawrence river near the city of Brockville. On 
the south the area of the Paleozoic rocks extends across the St. Law- 
rence into the state of New York, where there is a large development 
of the Calciferous limestone and the Potsdam sandstone, which also in 
many places are there seen to rest upon the crystalline rocks. 
R Sec. IV , 1900. 5a. 
