GEOLOGY OF THE TOEONTO EEGION 



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^&nd other rocks are apt to be squeezed into 

 synclinal bands between the oval gneissoid masses. 

 This )S 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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