GEOLOGY OF THE TORONTO REGION 



PALAEOZOIC. 

 ORDOVICIAN. 



The rocks of the Archaean are usually well 

 exposed on the flanks of hills, while the valleys are 

 more or less drift-covered ; but the Palaeozoic rocks 

 seldom rise as hills and their beds have only a slight 

 dip, so that they are commonly buried under boulder 

 clay or old lake deposits. Their outcrops are to be 

 looked for mainly along lake shores or river valleys 

 and there are hundreds of square miles of southern 

 Ontario where no exposures of solid rock have been 

 found. 



The Ordovician (Lower Silurian or Cambro- 

 Silurian) forms the bed rock in most of the Toronto 

 region, occurring at many points on the shore of 

 Lake Ontario and less often at a distance from it. 

 The subdivisions usually recognized are as follows: 



Queenston. 

 Lorraine. 



~ , Utica. 



Ordovician { ~ ,,. , 



Collmgwood. 



Trenton. 

 Black River. 



Feathering out toward the north upon the uneven 

 surface of the Archaean peneplain south of Bala, 

 Washago and other points between Georgian Bay and 

 the Thousand Islands one finds solid beds of Black 

 River limestone. They are well exposed in quarries 

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