BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 33, pp. 553-570 September 30, 1922 



RECONNAISSANCE OF THE EASTERN ANDES BETWEEN 

 COCHABAMBA AND SANTA CRUZ, BOLIVIA 1 



BY KENNETH C. HEALD AND KIRTLEY F. MATHER 



(Presented before the Society by the Senior Author December 29, 1921) 



CONTENTS 



Page 



Introduction 553 



Physiography 555 



The area examined 555 



The Cordillera Oriental 555 



Santa Cruz plains 556 



Stratigraphy 558 



Character of the rocks 558 



Arani formation 558 



Totora formation s 559 



Materal formation 560 



Bermejo formation 561 



Cajones limestone 565 



San Ysidro formation 567 



Quaternary 569 



Structure 569 



Introduction 



The eastern Andes of central Bolivia were crossed by the authors in 

 December, 19 19, during the progress of geological exploration for Rich- 

 mond Levering and Company, whose courtesy makes this paper avail- 

 able. The observations made during the traverse, 200 miles long and 

 10 days in duration, between Cochabamba, on the west, and Santa Cruz, 

 on the east, were rendered more comprehensive and understandable by 

 subsequent work north and south of Santa Cruz, along the east front 

 of the mountains. 



Our exploratory expedition left Cochabamba on December 3 and pro- 

 ceeded by train to Arani, the terminus of a short narrow-gauge railway, 

 which now (October, 1921) is being extended farther eastward toward 



1 Manuscript received by the Secretary of the Society February 3, 1922. 



(553) 



