THE GEOLOGICAL KNOWLEDGE OF THE NORTH 

 ATLANTIC CLIMATES OF THE PAST 



Martin Schwarzbach 



Geologisches Institut, Universitat Koln, Cologne, Germany 



The climatic history of the northern Atlantic is of great importance for the 

 understanding of the history of the biota in this region. But we can recon- 

 struct it only in fragments. This is caused partly by the fact the the sea- 

 covered areas of the Earth give only few outcrops and insights to the geologist ; 

 the islands are an exception, but there are not many in the northern Atlantic. 

 It is true that the situation has improved since it is now technically possible to 

 bring up cores from the ocean floor. Thus we can gain at least some additional 

 facts about the Quaternary and in part the Tertiary too, and this is, of course, 

 the time which is especially interesting for us. But as concerns the Pre- 

 Tertiary period, we can rely only on the adjacent continental areas, i.e. 

 Europe and North America, and on Greenland and some other islands. 



Here we have to wholly disregard Iceland, at least at first, for there are no 

 known sediments older than Tertiary. The oldest rocks of the island are 

 basalts. It is not impossible that this volcanism began in the Upper Cretaceous 

 as it is supposed to have done in Greenland, but that is without special 

 importance for the climatic history, and only the plant-bearing Tertiary beds 

 of Iceland reveal something about it. 



We can distinguish 4 or 5 great divisions in this climatic history. Their 

 time-span varies greatly, and they are known to be very different in kind. 

 In part they differ considerably as regards climate. Their respective boundaries 

 are arbitrary, partly conditioned by the state of the investigation. These 

 divisions are : 



1. Pre-Cambrian, 



2. Eocambrian. 



3. Paleo- and Mesozoic. 



4. Tertiary. 



5. Quaternary. 



I. PRE-CAMBRIAN 



The Pre-Cambrian, i.e. the period which is older than 600 million years. 

 can be treated in a few sentences because we know nearly nothing of it. 

 Neither the large Pre-Cambrian areas of Scandinavia nor those of Canada or 



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