12 MARTIN SCHWARZBACH 



Greenland with their generally highly metamorphic rocks give us sufficient 

 paleoclimatic information. Moreover, we do not know the paleographic 

 situation in the North Atlantic region at that time. It is true that the Lewisian 

 gneisses of the Scottish Hebrides are regarded as equivalents of the Canadian- 

 Greenlandian shield. Hans Stille (1958), for instance, draws an eastern 

 projection of this shield which comprises the northern Atlantic including 

 Iceland; he called it "Laurentia Minor" (in analogy to the projection of Asia 

 Minor). But that is an hypothetical, though possible, idea. 



It is, therefore, impossible to say how far the North Atlantic region was 

 temporarily influenced by a glacial climate like the one presumed for Canada 

 in Huronian time — perhaps 1 billion years B.P. — taking the cobalt tillites into 

 consideration. 



2. EOCAMBRIAN 



The first important fix-point at the turn of the Pre-Cambrian to Cambrian 

 is in the so-called Eocambrian. This period is short, extending approximately 

 some 100,000 or, at most, some million years; it has an age of perhaps 600 

 million years. But in many places it is characterized very well by moraine-like 

 sediments, the so-called "tillites". There is no doubt that many of these are 

 not true morainal deposits but pseudo-tillites. The stratigraphical position is 

 also uncertain in many cases, but there remains a lot of locahties where we 

 must suppose glacial activities, especially in regions surrounding the North 

 Atlantic. Investigation of those phenomena started first in the Norwegian 

 mountains. Now we do also know such deposits from Sweden, Spitsbergen, 

 eastern and northern Greenland, and farther — but more doubtfully- — from 

 the British Isles, Normandy, and eastern Bohemia. At typical localities we 

 find poHshed and striated boulders, striated pavement, and superposition of 

 fossiliferous Cambrian. Not so clear are the occurrences in North America. 

 But the above-mentioned tillites found between Greenland and Sweden make 

 it nearly certain that there was an Arctic climate with big glaciers or inland 

 ice in the North Atlantic area during the Eocambrian. 



It is remarkable that nearly all these tillites are situated in regions with a 

 recent or Pleistocene glaciation. Therefore they should actually present no 

 more problems than the Quaternary Ice Ages do. However, there are also 

 occurrences in other continents, and these make the Eocambrian Ice Age a 

 puzzle. 



3. PALEO- AND MESOZOIC 



The following division of the Paleo- and Mesozoic comprises ca. 500 

 million years — a very long period. But it is possible to treat it collectively for 

 it presents rather uniform chmatic features. There is much climatic informa- 

 tion available in Europe and North America, Greenland, and Spitsbergen. 



