4 STUDIES IN GEOLOGY, No. i 



unraveling some of the disputed and unsolved problems of 

 its geology. That they can not contribute the last word 

 they are fully aware; but their work has resulted in several 

 distinct additions to the subject. These consist primarily 

 in the first geologic map of Corocoro and vicinity, the first 

 measured sections of the Vetas and Ramos formations, the 

 recognition of the Desaguadero formation, and a more 

 exhaustive study of the flora of the Vetas formation. Credit 

 for whatever additions the authors may make to the geology 

 of the district must be shared with the management of the 

 two operating companies, as the work of 1915 and of 1919 

 was possible only through their aid and co-operation and 

 the facilities furnished by them. It is only fair to say 

 further, and with most enthusiastic appreciation, that credit 

 is due particularly to Mr. Fernando Dorion, general 

 manager of the Corocoro United Copper Mines, Ltd., and 

 members of his staff, who were not only always ready to 

 co-operate in and facilitate the work, but manifested an 

 interest and expectation in the results in no wise less than 

 that of the authors themselves. 



LOCATION 



The city of Corocoro is the capital of the province of 

 Pacajes of the department of La Paz and has a population 

 of about 10,000 inhabitants, almost exclusively Indian. 

 Topographically, it is situated toward the western edge of 

 the altiplanicie, or high plateau of Bolivia, in one of the 

 numerous groups of low hills that rise above the level of 

 the plain, at an altitude of a little over 13,000 feet. The 

 houses are strung out along several small valleys and gulch- 

 es at the foot of the north slope of the Cerro de Corocoro, 

 and the mines are located on the hills immediately surround- 

 ing the town. 



Until 1912 Corocoro was without railroad facilities. 

 Access to the district was then by muleback or stage from 

 La Paz, loo km. to the northeast. Ingress and egress of 



