ICE AGE IN NORTH AMERICAN ARCTIC — FLINT 251 



cf the glaciers from their former great extent. As recorded by a 

 variety of features, chiefly in the glacial drift, the shrinkage seems 

 to have been generally concentric, inward toward a "last stand" of the 

 shrunken main body of the ice sheet in the regions of Hudson Bay 

 and the Quebec-Labrador highlands. But wherever there were con- 

 spicuous highlands their cold and moist climates favored the per- 

 sistence of glacier ice upon them. Thus southeastern Quebec, Labra- 

 dor, and Baffin and Ellesmere Islands and their high-standing neigh- 

 bors, as well as Greenland, continued to nourish glaciers of various 

 kinds separate from the main residual ice body. Some of these sepa- 

 rate glaciers, notably the Greenland Ice Sheet, persist today despite 

 a somewhat unfavorable climate and conspicuous contemporary 

 shrinkage. 



EVIDENCE OF REPEATED GLACIAL AGES 



Most of the evidence that glaciation was repeated comes from the 

 temperate region, where the southern margins of the great glaciers 

 piled up at least four overlapping layers of drift, each separated from 

 the one below it by a zone of deep weathering-decomposition that in- 

 dicates a lapse of perhaps hundreds of thousands of years. During 

 each glacial age most of the arctic region lay beneath ice, and in the 

 mountainous areas the intensity of glacial erosion favored the destruc- 

 tion of earlier-formed drifts. Hence, as yet, the Arctic has contributed 

 little to our growing knowledge of the succession of glacial ages. In 

 no arctic locality has clear evidence of more than two glacial ages 

 yet come to light. If the Arctic alone were considered, this fact might 

 be taken to mean that glaciers continued to cover much of the arctic 

 region during the interglacial ages proved to exist in lower latitudes. 

 But when the whole glaciated region is examined, such a condition is 

 seen to be very improbable, for the fossil plants and animals contained 

 in some of the interglacial deposits imply arctic climates as warm as, 

 or warmer than, those of today. This in turn implies very widespread 

 deglaciation. 



Within the arctic region perhaps the best evidence of repeated gla- 

 ciation is a series of exposures in the district south and west of James 

 Bay (McLearn, 1927, pp. 30C-31C) . Here, between two sheets of till, 

 is a layer of peat, the compressed remains of a spruce-pine-birch-fir 

 forest. Clearly there were two glaciations of this district and, al- 

 though the length of the intervening time is not evident, it is probable 

 that both glaciations are of very late date. 



In the Carmacks district, Yukon, there are present two till sheets 

 of which the younger contains firm, fresh stones while the stones in the 

 older are thoroughly decomposed. A long interglacial process of soil 

 formation is indicated (Bostock, 1936, p. 48) . 



