FOSSIL PLANTS FKOM BOLIVL^ AND THEIR BEARING 

 UPON THE AGE OF UPLIFT OF THE EASTERN ANDES. 



By Edward W. Berry, 

 Of the Johns Hopkins University, Baltimore. 



INTRODUCTION. 



The present contribution includes a description of the fossil plants 

 from two weU-known localities in Bolivia — the copper district of 

 Corocoro and the silver and tin district of Potosi — both classic local- 

 ities that have been worked since the sixteenth century. The rather 

 definite results regarding the age of these deposits has not only an 

 important bearing on the time of mineralization in these regions, but 

 is of the greatest value in mdicating the period of elevation of the 

 Andes, which is shown to be much later and more profound than has 

 hitherto been supposed. This study is based upon material col- 

 lected in 1915 by Profs. J. T. Singewald, jr., of the Johns Hopkins 

 University, and Benjamm L. MiUer, of Lehigh University. The 

 types and figured specimens have been presented to the United 

 States National Museum . A discussion of the results of this study is 

 followed by a description of the flora, and by an account of a new 

 species of Brachiopod contributed by Prof. Charles Schuchert, of 

 Yale University. 



PRESENT PHYSIOGRAPHY AND CLIMATE. 



A brief outline of the present physiography, geology, and climate 

 of Bolivia are necessary to an understanding of the bearing of the 

 fossil floras discussed in the following pages on the geological history 

 of the region. 



Although lying wholly within the Torrid Zone the combination of 

 elevation, mountain barriers, and prevailing winds has had a most 

 profound influence on the climate, and consequently upon the flora 

 and fauna. Except for certain transverse and irrigated valleys and 

 the relatively low and barren Coast Range the country bordering the 

 Pacific (now belonging to Chile) is a desert of shifting sands. This is 

 bounded on the east by the Western Andes or Cordillera Occidental, 

 which parallels the coast at a distance of from 50 to 100 miles. ^ 



1 The relatively low Coast Range Is omitted, as It is of no importance in the present connection. 



Proceedings U. S. National Museum, Vol. 54— No. 2229. 



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