GEOLOGY OF THE TORONTO REGION 
all crystalline rocks of eruptive origin, the dark 
green diorite or gabbro or hornblende schist being 
earlier than the flesh-colored granite and gneiss. The 
schistose cleavage generally to be observed in these 
rocks has a steep dip in most cases, and when traced 
for a distance tends to sweep as wide curves. The 
mapping of a considerable area usually shows that 
the granite masses are oval in shape and pass out-' 
wards into gneiss, the quartz and feldspar and mica 
taking on a parallel arrangement; while the green- 
schists and other rocks are apt to be squeezed into 
synclinal bands between the oval gneissoid masses. 
This is the arrangement characteristic of the batho- 
lithic type of mountain structure, and the present 
surface of hummocky hills displays a cross section 
through the base of former batholithic domes, long 
ago carved down to mere stumps. 
Near Parry Sound rocks of the Grenville series, 
mica schists and fine-grained gneisses with crystalline 
limestone or marble, have been caught in the moun- 
tain-building process and are found in long bands 
between the elongated domes of granite and gneiss. 
In all cases the metamorphosed sediments just men- 
tioned, and the green eruptives which have been 
upheaved by the ascending granite of the domes, are 
the oldest rocks. They formed the cold and solid 
crust which was invaded by the molten granite. 
The later members of the Archaean, such as the 
Huronian, have not been found in the region within 
100 or 150 miles of Lake Ontario, and the next for- 
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