STRUCTURAL RELATIONS OF PRE-CAMBRIAN AND PALAEOZOIC. 3 
The Hastings Road section, according to these geologists, shows 
a thickness for the Grenville series of 9,440 feet or 1*788 miles. 1 
In some areas the intrusive element of the Archaean, represented 
chiefly by great granite batholiths, predominates, while in others 
interbedded limestone and other sediments of highly altered 
character are comparatively free from igneous intrusions. In 
the Burleigh-Chandos section of the Haliburton and Bancroft 
areas, there is 8,350 feet of limestone out of a total of 17,824 
feet. 2 This great series of Pre-Cambrian sediments shows, 
nearly everywhere, highly inclined beds which seldom have 
dips of less than 45 degrees. Upon the truncated and profoundly 
eroded edges of these ancient and highly altered sediments the 
Palaeozoic beds rest with approximate horizontality. 
The basal beds of the Palaeozoic series begin with different 
members in different parts of the Palaeozoic areas. Throughout 
much, but not all, of the Palaeozoic area, the Potsdam sandstone 
forms the base of a Palaeozoic section which comprises sandstone, 
shale, and limestone. The Potsdam is unknown above Quyon on 
the Ottawa river and appears to be absent west of Kingston. 
East of Quebec the Potsdam is absent and the section begins with 
a later horizon of the Trenton than occurs farther west. The 
Palaeozoic section appears to reach its maximum thickness south 
of Montreal where deep wells have penetrated the Palaeozoic to 
a depth of 2,400 feet without reaching the base of the series. In 
the Ottawa valley the Palaeozoic section apparently attains its 
maximum thickness a few miles southeast of Ottawa where the 
beds have a total thickness of more than 2,000 feet. The Ottawa 
well section (Somerset street) shows that 1,276 feet of this thickness 
is below the top of theTrenton. The Queenston red shale (“Lower 
Medina'’) is the youngest formation to escape complete denuda- 
tion, if we except the unique remnant of Devonian beds at Mont- 
real. The Queenston shale is represented by small remnants 
in the Ottawa district and in the St. Lawrence valley northeast of 
Montreal. The Nicolet River section, together with the record 
of deep wells near St. Hyacinthe, shows the Queenston red shale 
northeast of Montreal to have a thickness of 1,000 feet or more. 
1 Adams and Barlow, Geol. Surv., Canada, Mem. No. 6, 1910, p. 33. 
2 Idem, p. 35. 
