NORTH ATLANTIC CLIMATES OF THE PAST 1 3 



Not only floras and faunas, but also sediments give valuable information, 

 especially the rather thick Hmestones and the evaporites. 



If we consider only Greenland and the other Arctic islands in this connec- 

 tion, we must mention the limestones of the Cambrian and Ordovician, the 

 Old Red beds in east Greenland, the coals of the Upper Devonian and Lower 

 Carboniferous on Bear Island and Spitsbergen, gypsum beds in the Upper 

 Carboniferous of Spitsbergen and Greenland, reefs in the Rhaeto-Liassic of 

 Jameson Land, in the Cretaceous of Kome, Atane, and Patoot in western 

 Greenland, Spitsbergen, and King Charles Land. 



All these occurrences prove the same thing : that for a very long time there 

 was a climate completely different from today. There was no Arctic; not 

 just a moderate, but a warm or very warm chmate existed. In another connec- 

 tion 1 have explained comprehensively that the North Atlantic belonged to the 

 tropical reef-belt during the Paleozoic; Franz Lotze (1957) has shown that 

 also the Paleozoic belt of the northern evaporite zone, i.e. the hot desert belt 

 of the Earth, was situated there. In the Mesozoic, the temperatures were 

 already somewhat lower, e.g. in Greenland, and the northern boundary of 

 the reef corals shifted farther to the south. But the Mesozoic floras prove that 

 very favorable chmatic conditions were still present. 



The Rhaeto-Liassic floras of Jameson Land alone have revealed some 200 

 diff'erent species. I mention further the famous leaves and fruit of the bread- 

 fruit tree, Artocarpus, described in 1890 by Nathorst from the Cretaceous of 

 Greenland. 



I would hke to add that the modern direct measurements of temperature 

 with the aid of O^^jO^^ isotopes fit in rather well with the geologically deter- 

 mined climate. Belemnites from the Scottish Jurassic gave sea temperatures of 

 17-23°C, from Alaska of 17°. That is somewhat more than 10° higher than 

 today. 



It is not yet possible to say if there were large cUmatic fluctuations in the 

 Paleo- and Mesozoic of the northern Atlantic. Their existence seems possible, 

 especially at the turn of the Carboniferous-Permian with the big inland 

 glaciations of the Southern Hemisphere. But the influence of the Gondwana 

 Ice Ages must not have been large, in analogy with the small influence which 

 the Quaternary glaciations did show in the tropics. 



In any case, we do not find positive indications for cool temperatures in the 

 northern Atlantic and its surroundings. There are almost no tilhtes of 

 Paleo- or Mesozoic age. What has been described as such is very uncertain, 

 taking for instance the much-mentioned Squantum tillite near Boston; its 

 glacial origin is as doubtful as its stratigraphic position. 



This is not the right occasion to discuss the cause of the warm climate in 

 the North Atlantic region during Paleo- and Mesozoic time. But it must be 

 emphasized that another position of the pole and the equator would be a very 

 good explanation, at least in the Paleozoic. This fits in very well with modern 



