524 REPORT— 1898. 



found along the Don Valley extend "widely beneath the clays of the 

 region, and that the warm-climate beds underlie the cold-climate beds 

 conformably. As the Don beds rest upon a layer of boulder clay, and the 

 cold-climate beds are covered by another layer of boulder clay, both are 

 clearly inter-glacial. 



Professor Chamberlin, of Chicago University, has suggested the name 

 ' Toronto formation ' for these fossilif erous deposits, and thinks that they 

 probably occupy the interval between the lowan and Wisconsin till sheets, 

 and are a possible equivalent of Dr. James Geikie's ISTeudeckian, in the 

 Old World.' 



Starting from a level more than 40 feet below the surface of Lake 

 Ontario, the following section is found at Scarborough : — 



Feet 



G. Complex till with inter-bedded stratified sand and clay . . 200 



Great interval of erosion. 



5. Stratified sand with shells and trees of a cold climate . . 55 



4. Peaty clays with plants and beetles of a cold climate . . 95 



3. Clays and sands with unios and trees of a warm climate . . 35 



2. A lowest till of variable thickness — 



1. Eroded surface of Hudson River (Cambro-silurian) shales . — 



During the past year the area known to be covered by the unio beds 

 and the peaty clays has been greatly extended. The former have been 

 shown to stretch seven miles from east to west and a mile and a half from 

 north to south, indicating an area of ten square miles and possibly very 

 much more. The peaty clay has been followed seventeen miles from east 

 to west and six miles to the north of Lake Ontario. It probably covers 

 at least 100 square miles of territory. The two series, together witli the 

 overlying inter-glacial fossiliferous sands, are more than 185 feet in thick- 

 ness at Scarborough. 



We may look on the Toronto formation as representing a great delta 

 deposit in a lake extending some miles farther north than Lake Ontario 

 does at Toronto at present. At first this great inter-glacial lake stood 

 about 80 feet higher than the present water-level, and the climate was 

 like that of Ohio or Pennsylvania. The lake then deepened till its 

 surface stood at least 150 feet above the present Lake Ontario, and the 

 climate altered to one like that of Southern Labrador. 



We must suppose that these immense beds of clay and sand were not 

 deposited by feeble streams like the present Don and Humber, but 

 probably by an inter-glacial successor of Dr. Spencer's pre-glacial ' Lauren- 

 tian river,' draining the upper Great Lakes directly from the Georgian 

 Bay, instead of through the present circuitous route by Lake Erie and 

 Niagara. Even with so powerful a river the formation of these massive 

 inter-glacial beds must have required a great length of time. 



After they were laid down the inter-glacial predecessor of Lake 

 Ontario was drained below its present level long enough to allow various 

 small streams to erode wide valleys through the strata just referred to, 

 since the second till sheet fills in two or three such valleys, as shown at 

 the Scarborough escarpment. The time required for these erosive opera- 

 tions must have been long, perhaps as long as the time since the final 

 retreat of the ice from the region of Toronto ; and the whole length of 

 time demanded for this inter-glacial period cannot be less than five or ten 

 thousand years. 



' Jov/rnal of Geology, vol. iii., No. 3, pp. 273-275. 



