CHEONOLOGY DOUGLASS AND ANTEVS 321 



In the belt between Mattawa and Lake Timiskaming varved clay 

 is practically lacking. The ice retreat from the mouth of Montreal 

 Kiver on Lake Timiskaming to La Sarre on the Transcontinental 

 Railway northeast of Lake Abitibi took 1,208 years. Since the dis- 

 tance is 118 miles, this represents an average of 515 feet a year. The 

 rate was relatively uniform in wide belts, though it increased north- 

 ward. Later it became irregular, and when the ice front had reached 

 far north of Cochrane, it halted and began to move southward. This 

 readvance probably amounted to as much as 70 miles, for the ice 

 border finally reached Iroquois Falls and points 22 miles south of 

 Cochrane. Contemporaneous with the beginning of this readvance 

 the huge Lake Barlow-Ojibway, held in by the ice in the north, was 

 suddenly drained northwestward to Hudson Bay. This event took 

 place during the years 2,022 (or 2,015) to 2,027 after the uncovering 

 of the mouth of Montreal River on Lake Timiskaming. The drain- 

 age marks the end of the continuous varve chronology in these re- 

 gions, for subsequently there were only small, scattered lakes in 

 which varved clay could be deposited. At points farther east, how- 

 ever, it may be possible to extend the varve series toward the ice 

 center in the Labrador peninsula, though this is hardly profitable 

 until the wilderness of this region has become more easily accessible. 



In addition to these longer varve records, shorter ones comprising 

 from 100 to about 1,000 years have been obtained in New Jersey, 

 New York, New England, southeastern Quebec, the regions east and 

 north of Lake Huron, and northern Manitoba. Local glacial geology 

 has been correlated with these chronological fragments, which, it 

 is hoped, will ultimately be tied together with the longer varve 

 series. 



As touched upon, correlations of varve graphs from North America 

 and Europe are not possible. However, a correlation of the late- 

 glacial epoch in North America and Europe may be made on the 

 basis of the major changes of temperature that are recorded in the 

 rate of disappearance of the ice sheets. The climatic alteration that 

 set a stop to the growth of the ice sheets and introduced their wan- 

 ing was the greatest in late Quaternary time. Since its main factor 

 was a temperature rise, and since marked temperature changes in 

 the post-glacial epoch seem to have made themselves felt both in 

 North America and in Europe, it is more likely than not that the 

 last main ice sheets began to shrink at about the same time. If 

 they did not, the American ice sheet may have been the earlier to 

 commence waning, not vice versa. It is therefore probable that, gen- 

 erally speaking, the peripheral belts of the two main areas of glaci- 

 ation were uncovered at the same time. In the region between the 

 south side of Lake Ontario and Mattawa River, which forms the 



