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. 
GriaciaL DeEposits. 
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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