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 stratified 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 section 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.