34 STUDIES IN GEOLOGY, No. i 



Meters 



.9 Brown shale grading into sandstone 

 2.8 Light gypsiferous sandy clay and brown sandstone 

 10.6 Reddish-brown shale 

 .6 Sandstone 



31.6 Brown hackly shale 



2.5 Sandstone, brownish below, greenish and more gypsiferous 



above 



3.4 Hackly brown clay, copper at base 



5 Gypsiferous sandstone 



23.4 Red shale, badly weathered 



2.0 Cupriferous gypsum 



21.7 Light-brown gypsiferous clay 



. 35.0 Red gypsiferous shales with bands of gypsum at intervals 



.6 Contorted cupriferous gypsum 



167 Red, very gypsiferous shale 



3 Copper band 



81.4 Red, gypsiferous shale 



160.1 Covered in Corocoro valley across town 

 Bed at top of preceding section 



The entire measured section of the Ramos beds includes 

 81 per cent shales, 18.7 per cent sandstones, 0.3 per cent 

 conglomerates.' The shales are light-red to dark-red in 

 color and at some horizons grade into brown. Thin inter- 

 calations of green shale are abundant. The sandstones 

 show the same range in color as the shales, except that near 

 the fault are several horizons of gray sandstones similar to 

 the gray sandstones of the Vetas formation. The color of 

 the Ramos formation is, therefore, more pronounced red 

 than that of the Vetas formation. 



Gypsum is a prominent feature of the Ramos strata, 

 occurring both as beds and as impregnations, veinlets, and 

 stringers, through the rocks. North of Corocoro and south 

 of the Pontezuelo River is a group of dull-gray to white 

 hills called the Cerros Blancos, covering an area of 3 kilo- 

 meters long from north to south and nearly 2 km. wide from 

 east to west. The color of these hills is due to the abundance 

 of gypsum in the rocks which seems to have grown by 



