COROCORO COPPER DISTRICT OF BOLIVIA 9 



the Vetas formation tend to be lighter in color than those 

 of the Ramos. Another important feature emphasized by 

 him is the abundance of igneous material entering into the 

 composition of these beds in the form of tuffaceous and 

 conglomeratic material. Indeed, Sundt himself comments 

 upon the fact that he is the first to recognize this. 



Dereims merely says that the Corocoro beds belong to 

 the Permian whi-ch extends over a great area on each bank 

 of the Desaguadero, and that they are everywhere identical 

 in mineralogical composition, consisting of rose-colored and 

 red sandstones and red shale with gypsum and salt. 



Steinmann considers both the Vetas and the Ramos 

 series members of his Puca sandstone formation. He says 

 that red sandstones are found in Bolivia ranging in age from 

 Silurian to Quaternary, but the thickest series (several 

 thousand meters) and most widely distributed is that which 

 covers a larger part of the high plateau and the eastern 

 range of the Andes. To this series he has given the name 

 Puca sandstone, from the Quechua word puca, which means 

 red. He describes the series of rocks as resembling very 

 strikingly the German Buntsandstein. Aside from local 

 intercalations of dark shales and dark, basic, porphyritic 

 rocks, and still more local limestone intercalations, the 

 prevailing rock, he states, is a red, medium to fine-grained, 

 occasionally conglomeratic sandstone of light to brilliant 

 red, but also dark-red or violet color. Cross-bedding is 

 common and carnelian nodules are occasionally encountered. 



"Almost everywhere the formation can be readily separated into 

 three divisions : a lower, consisting entirely of sandstone ; a middle, 

 in which red shales, often associated with gypsum and occasionally 

 with salt, prevail, and in the lower part of which the fossiliferous 

 limestones occur; and an upper, which includes the greater part of 

 the sandstone series." (p. 341) 



The Vetas formation Steinmann considers to be the lower 

 member of his Puca sandstone and the Ramos formation 

 the middle member. The age of the Puca sandstone as 

 determined by the fossils from the limestones is Cretaceous. 



