ii2 STUDIES IN GEOLOGY, No. 4 



if proof be necessary, that the prevailing winds of those times 

 were westerly as they are today. . 



What is more interesting they show that there was abun- 

 dant volcanic activity in the Miocene. This in itself would 

 seem to indicate the presence of mountains such as have not 

 been demonstrated in the Andean region farther north. 

 Some further evidence on this point is furnished by a consid- 

 eration of the contemporaneous climate of Patagonia. The 

 time has perhaps not yet arrived for a precise evaluation of 

 the climatic conclusions to be derived from the wonderful 

 assemblage of mammals described by Professor Scott from 

 the Santa Cruz beds of Argentina. It is a great pity that the 

 contemporaneous flora of that region has not been discovered. 

 The Santa Cruz vertebrates predominate in plains types, the 

 discovered birds are flightless forms, and no snakes, croco- 

 diles or tortoises have been found. The arboreal forms are 

 limited, but include tree porcupines, and there were hosts of 

 ground sloths. This evidence may all be negative, but it 

 seems plausible to suppose that the country was a plains or 

 savanna country lacking forests except in scattered clumps 

 and along streams. Hence the precipitation was less than 

 in the corresponding region, of Chile, although the evidence 

 that the climate of Patagonia at that time was more genial 

 than at present is overwhelming and everywhere admitted. 



If the Patagonian climate was drier than that of Chile 

 in Miocene time, and the available evidence points in that 

 direction, the only plausible explanation is the presence of an 

 intervening mountain chain that also contained the volcanoes 

 that were the source of the ashes so much in evidence in 

 southern Argentina. The Miocene climate did not, however, 

 furnish the extreme contrast that the present climate of Pata- 

 gonia and southern Chile exhibits and both the Chilean fossil 

 flora and the Patagonian fossil vertebrates are in concor- 

 dance in proving that at that time more genial climatic 

 conditions prevailed far to the southward of their existing 

 limits. 



