GEOLOGY OF tHE TORONTO REGION 



valley, which it entered near Toronto. Probably 

 the Ontario basin did not then exist and the valley 

 sloped eastwards toward the sea. 



When the first record begins the surface possessed 

 a higher relief than now, the escarpment rising as 

 cliffs of 300 or 400 feet, and the old river valley at 

 Toronto having a depth of at least 200 feet below the 

 general level. 



GLACIAL DEPOSITS. 



The greater part of the region is covered with 

 glacial deposits, especially boulder clay, and mor- 

 aines are frequent, sometimes rising as tumultuous 

 hills as in the Oak Ridges north of Toronto, at others 

 having low and inconspicuous forms. They have 

 been worked out in much of the region by Mr. F. B; 

 Taylor, but no general map of the glacial deposits 

 has yet been published. With the moraines in 

 various places there are kame deposits of coarse 

 gravel and sand where sub-glacial rivers emptied, 

 and in some cases narrow esker ridges of sand indi- 

 cate the course of such rivers beneath the ice. The 

 general surface of the boulder clay is apt to be gently 

 rolling, as north of Toronto, but in some places there 

 are drumlin hills of a more striking kind. 



The boulder clay is charged with a great variety 

 of stones, including Archaean rocks, such as granite, 

 gneiss, diorite and crystalline limestone, and Palaeo- 

 zoic rocks, such as limestones, shales and sandstones 

 of the Ordovician. The matrix is commonly bluish 

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