8 
MUSEUM BULLETIN NO. 8, 
overlies the greywacke or the quartzite member of the lower 
series, so there is evidence of a considerable unconformity. 
Nevertheless, exact contacts are rarely visible and the very 
existence of the break in the succession is seldom appreciable. 
The basal conglomerate of the upper series is from 50 to 
125 feet thick and passes upward into 600-800 feet of white 
quartzite. This quartzite becomes dark and argillaceous at the 
top and in a thickness of 200 feet merges into what is usually 
called the upper slate conglomerate formation. In reality this 
is a complex alternation of greywacke, boulder conglomerate, 
quartzite, and finely laminated greywacke and greywacke- 
conglomerate. The succession as observed north of Rock lake 
is shown in Figure 3. On account of its distinctive lithological 
characters and great thickness (2,600-3,000 feet) this member 
is of more than ordinary importance for correlation of the suc- 
cessions in the various areas under discussion. 
The upper slate conglomerate group terminates in a Icimin- 
ated greywacke, which grades imperceptibly in 200-300 feet 
into a dull red, impure quartzite,, the base of the great upper 
quartzite formation. This quartzite, 5,500-6,000 feet thick, is 
dull red and impure at the base, but grades in about 1,000 feet 
into a white quartzite, which becomes still purer toward the 
top. About the middle of the formation the white quartzite 
carries conglomerate beds of small, well rounded pebbles of white 
and grey quartz and red jasper. Logan and Murray regarded 
these different phases of the quartzite as distinct formations, 
naming them the red quartzite, red jasper conglomerate, and white 
quartzite formations, but such a subdivision appears arbitrary 
and apt to obscure the fact that all three represent one continuous 
process of deposition. 
The white quartzite passes gradationally upward into 700 
feet of finely banded, chert-like quartzite, the individual beds of 
which are 12 inches or less thick and are coloured grey, buff, 
greenish, or white. This is the highest member of the upper 
series that occurs within Bruce area, but Logan and Murray 
record above it a white quartzite 1,500 feet thick, yellow chert 
and limestone 200 feet, and white quartzite 400 feet thick. 
