NATURAL HISTORY, TORONTO REGION 
glacial episodes was long, and that it included great 
changes of climate and of physical conditions is 
proved by the extent and character of the deposits 
and by their fossils. This set of interglacial beds, 
which has been called the Toronto Formation, 
includes a thickness of 185 feet of sand and clay 
deposited as a delta by a great river flowing from 
the north into an interglacial Lake Ontario. 
_ Three outcrops are of special interest, one at the 
Don Valley brickyard, another at Scarborough 
Heights, and a third near Christie and Shaw Streets. 
At the brickyard, which is just east of Rosedale, the 
lowest boulder clay is seen resting upon the Lorraine 
shale, followed by 25 feet of stratified clay and sand 
containing many shells and leaves of trees as well as 
logs of wood. Above this there are 21 feet of strati- 
fied clay with a little peaty matter, but no other 
organic remains. This is followed by a second 
sheet of boulder clay and then by 80 feet of stratified 
clay from which no fossils of any kind are known. 
Boulders on the Iroquois terrace above imply a third 
boulder clay removed by wave action. 
The fossils from the Don valley interglacial sec- 
tion include a dozen species of the Unionidae, four of 
which now live in Lake Ontario, three others in 
Lake Erie, while the other five do not occur in 
Canada but are found in the Mississippi waters. 
There are in addition twenty-nine species of smaller 
shells. 
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