10 
MUSEUM BULLETIN NO. 8. 
fault. On both sides of the fault, dykes and larger bodies of 
diabase like that of Bruce area invade these sediments and 
the crystalline basement. 
The sediments overlying the crystalline basement are 
separated by an unconformity into lower and upper series as 
in Bruce area, and the succession in each is much the same 
as in that area. The basal member of the lower series is a feld- 
spathic quartzite 1,500 feet, and possibly 2,000 feet thick. It 
rests immediately upon a surface of decayed granite. The 
unaltered granite beneath grades imperceptibly upward into 
2 or 3 feet of decomposed, disintegrated granite, now recemented 
into a greenish granite devoid of dark minerals, and this, in its 
turn, into an arkose of much the same composition but in which 
rounded quartz and feldspar grains, and even an occasional 
small quartz pebble, are perceptible. A little higher up the 
arkose carries a few pebbles of quartz but there is no pronounced 
basal conglomerate like that found on the islets near Thessalon. 
The arkose changes in the first 100 feet into a more or less 
■feldspathic white quartzite which varies but little in lithological 
character from there to the top; the only variations are some 
thin conglomerate beds carrying well-worn pebbles of white 
and grey quartz and about 150 feet of a dark grey, fine-grained 
quartzite. 
Except in one place, this is the only member of the lower 
series that survived the subsequent Pre-Cambrian erosion. On 
the Lake Huron coast a mile west of Blind river a few feet 
of banded, siliceous limestone like that of Bruce area also remain. 
This vestige of limestone is overlain directly by 60 feet of con- 
glomerate carrying numerous limestone pebbles. Both for- 
mations at this place are on edge and the line of contact is 
slightly at variance with the bedding planes in the limestone. 
At various points on Lauzon lake and Lake of the Mountains 
this basal conglomerate of the upper series overlies the lower 
quartzite. The contact line is slightly undulating. The 
conglomerate is 60-125 feet thick and consists usually 
of large, closely packed, rounded boulders, up to 2 feet in dia- 
meter, of granite, gneiss, greenstone, crystalline schists, conglom- 
erate, greywacke, quartzite, and other rocks, but none of lime- 
