PROCEEDINGS 



OF THE 



AMERICAN PHILOSOPHICAL SOCIETY 



HELD AT PHILADELPHIA 

 FOR PROMOTING USEFUL KNOWLEDGE 



A POSSIBLE EXPLANATION OF UPPER EOCENE 



CLIMATES. 



By EDWARD W. BERRY. 



{Read April 21, 1922.) 



No single problem has awakened more interest among geologists 

 and botanists than the climatic significance of the fossil floras discov- 

 ered in Arctic lands. This interest, although losing some of the zest 

 of novelty, has remained unabated since the first announcements by 

 Professor Heer nearly two generations ago, down to the present. A 

 great variety of hypotheses have been advanced to explain their ap- 

 parent anomalous distribution. These range all the way from Neu- 

 mayr's naive suggestion that organisms have completely changed their 

 environmental requirements during the ages to the thesis recently 

 advanced by Knowlton^ that Cretaceous and Tertiary climates, as well 

 as those of earlier geologic periods, were controlled by earth heat, and 

 were not subject to solar control, as they are at the present time. 



Everyone will, I think, admit that the faunal and floral evidence 

 throughout the major part of geologic time, in so far as it is known, 

 indicates a greater uniformity of climatic conditions and less contrast 

 between high and low latitudes than exists at the present time. There 

 are few, however, who will deny that there were contrasts at all times 

 between high and low latitudes. Throughout most of known geologic 

 time climatic zones appear less marked than now, and I believe that 

 we can rely on the validity of appearances on this point. There are, 

 however, several times in the past when climatic zones were sharply 

 marked, and all of these were at times of land extension and sea 



1 Knowlton, F. H., Geol. Soc. Amer., Bull, Vol. 30, pp. 499-566, 1920. 



PROC. AMER. PHIL. SOC, VOL. LXI, A, AUG. IC, I922. 



