NORTH ATLANTIC CLIMATES OF THE PAST 17 



the distribution of Tertiary mammal faunas in Europe-Asia-North America 

 do not require such a land-bridge. 



it is to be hoped that the study of deep-sea cores will give more certain 

 answers to these questions. 



5. QUATERNARY 



The Quaternary Ice Age which began ca. 1 milHon years ago is of greatest 

 importance for the recent flora and fauna of the North Atlantic regions. 

 Nevertheless, we can treat it relatively briefly. One fact stands without doubt : 

 that these areas were covered more or less completely by ice during Glacial 

 times; looking out of the windows of the University of Reykjavik, we see 

 ice-polished rocks all around us. 



But there remain some questions of special interest: 



1. What was the detailed course of the Ice Age, i.e. the succession of 

 Glacials and Interglacials ? 



2. Where were the ice-free refugia? 



3. What about Quaternary land-bridges? 



The first question concerning the stratigraphy of the Quaternary Ice Age 

 can be answered only on a large scale. Generafly ice-bordered and temporarily 

 ice-covered areas are much less fit for a detailed stratigraphic division than 

 more distant regions. This is due to the fact that ice-erosion often removes 

 older deposits completely. But still it is certain also that in the polar regions 

 Glacial periods alternated with Interglacials in which climate, and vegetation, 

 were about the same as today or even a httle more favorable. There are 

 several known Interglacials in Iceland, for instance from Snaefeflsnes and 

 from the neighborhood of Reykjavik, and Thorarinsson will tell us something 

 about new finds in southern Iceland. Likewise, it seems to be certain that 

 these Interglacial floras and faunas belong to several, i.e. temporally different, 

 Interglacial periods. 



There are also Interglacials in Greenland, from where Bryan (1954) 

 described an occurrence of Picea mariana, and also in Alaska and Arctic 

 Canada (Terasmae et al. ; cf. Craig and Fyles, 1961). 



Until now it has been completely impossible to equate all these Inter- 

 glacials with the standard divisions of Europe or North America. 



But the studies of deep-sea sediments will perhaps help us to get better 

 results. The cores from the floor of the oceans prove a repeated alternation of 

 warm and cool periods, confirmed by foraminiferal faunas or directly isotopic 

 temperatures. The core no. 280, for instance — from the northern Atlantic at 

 35° N. Lat. — shows according to Emiliani (1958) a change between tempera- 

 tures of 11° and 18°C. The 11° record corresponds to a Glacial, the 18° to an 

 Interglacial time, with perhaps an age of 90,000 years. But most age calcula- 

 tions are very uncertain, especially for the periods beyond C^'* determinations, 



