GLACIAL AND INTERGLACIAL BEDS 301 



At Mr. Adare's sand pit a considerable number of fossils have 

 been obtained, including numerous campelomas, two or three 

 species of pleurocera, Valvata sincera, two or more species of 

 sphaerium, and fragments of unios, all shells which occur in 

 the Don beds. Beside these fossils bits of elephant tusks 

 and a large atlas vertebra, probably of Bison americanus 

 occur, but none of the species is decisive as to climate, though 

 the mammoth or mastodon suggests a cool climate. 



The sand and gravel beds have a thickness of at least 78 

 feet and rise 130 or 140 feet above Lake Ontario, but their 

 extent is unknown, as they are in general buried under bowlder 

 clay. It is certain that these beds were formed under different 

 conditions from those either of the Don or Scarboro'. They 

 are of coarser and more variable materials, often showing very 

 marked cross bedding, probably produced by currents rather 

 than waves, and sometimes apparent unconformities such as are 

 made by a stream changing its bed. We may suppose that an 

 interglacial Humber river coming in from the west or north- 

 west brought down sand and gravel at the edge of the great bay, 

 mingling them at some points with the clayey delta materials of 

 the Laurentian river. 



This brings to a close the series of deposits composing the 

 Toronto Formation. In all there are four varieties, the sands 

 and clays of the Don with their warm climate trees and Missis- 

 sippi unios ; the peaty clays of Scarboro' with their seventy 

 extinct beetles and their small flora, suggesting a cool, but 

 not arctic climate ; the stratified sands overlying them, prob- 

 ably forming a continuation of the cool climate period ; and 

 the western sands and gravels with elephants, bisons and some 

 shellfish affording little evidence as to climate. The maximum 

 thickness observed in each set of deposits is as follows : 



3. Scarboro' sands - - 60 feet. ) 



2. Scarboro' peaty clays 94 " \ 4. Western sands and gravels, 78 ft. 



1. Don beds - - 41 ]/ 2 " ) 



I95X 

 The greatest thickness measured at one place is at Scarboro' 



