244 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 52 



epoch is also known as the "Ice Age," the latter term is not a good one ; 

 it is too simple. It does not imply that it includes the interglacial 

 ages, whose combined length was greater than that of the combined 

 glacial ages. 



Most of the information on which we have formed our concepts of 

 Pleistocene conditions comes from temperate regions. Knowledge of 

 the former glaciation of arctic regions is scanty and is based in part 

 on inferences from research carried on in lower latitudes. At pres- 

 ent our reconstruction of glacial and interglacial events in the Arctic 

 consists of broad generalizations, meagerly supported at one place or 

 another by detailed data. As exploration and research fill in the wide 

 blanks in our knowledge much will be learned that will modify our 

 concepts concerning the extent of the former glaciers, their growth 

 and decay, and the paths they made possible for large mammals and 

 for early man emigrating from northeast Asia into North America. 



EVIDENCE OF GLACIATION 8 



Today only a minor proportion of the arctic and subarctic regions is 

 covered with glacier ice. But it is now well known that during the 

 glacial ages a very large proportion of the land areas of these regions 

 was overspread by glaciers, while the seas were largely covered with 

 ice consisting of frozen sea water plus icebergs broken off from the 

 glaciers along the coasts. 



This knowledge is based on evidence of various kinds. Direct evi- 

 dence of former sea ice is little known as yet, but it is unmistakable. 

 In 1936 the Western Union Telegraph Co.'s ship Lord Kelvin made 

 a cable-repairing voyage from Canada to Britain. On board was 

 Dr. C. S. Piggot, who had invented a device for taking a 10-foot core 

 sample of the soft sediments beneath the sea floor. A study of the 

 series of cores he made from the region between Newfoundland and 

 Ireland showed that the sea floor in that region is underlain by al- 

 ternating layers of foraminiferal ooze and pebbly grit (Bradley et al., 

 1940). The single-celled Foraminifera contained in the ooze are 

 characteristic of the warm surface waters of the Gulf Stream. The 

 pebbly grit likewise contains some Foraminifera, but they are of types 

 peculiar to colder northern waters. 



There can be no reasonable doubt that the layers of pebbly grit were 

 deposited by sea ice as it floated southward and melted during glacial 

 times. The layers of foraminiferal ooze, on the other hand, were de- 

 posited under warmer conditions much like those of the present day. 

 Hence there is firm ground for the belief that in the glacial ages the 

 northern seas yielded sea ice that was far more abundant and that ex- 

 tended much farther south than at present. 



• Systematically discussed In Flint, 1947. 



