PLIOCENE PISLLYPAMPA BOLIVIA 149 



After the discovery of the lignite, mining claims or per- 

 tenencias were taken out and eight short drifts from the 

 stream level and one vertical shaft from the pampa surface 

 were opened, but at the time of my visit these were filled 

 with water to stream level, and as the drifts followed down 

 the dip, a very limited section was available for study. I was 

 fortunate, however, in having as a guide Sefior Serepio of 

 Cochabamba, who had originally discovered the outcrop and 

 who had been in charge of it during the development, so that 

 I was thus enabled to get data which I regard as fairly re- 

 liable regarding the total thickness of the deposit. 



The section is as follows : 



Recent or Pleistocene. FEET 



1 . Cobbly wash 2 



Pliocene. 



2. Compact buff tuff with fossil plants 8 



3. Similar material in thin seams alternating with lignitic 



layers usually i to 2 inches but sometimes 4 inches 



in thickness 4 



4. Brownish-buff, laminated, water laid clay with matted 



layers of mostly large leaf impressions 4 



5. Lignitic seam, consisting of irregular bands up to 8 or 



10 inches in thickness, with clay partings 3 



6. Beneath the water the guide reported definitely an 



argillaceous layer immediately below the second lig- 

 nite bed (No. 5) 4 



7 . Third lignite bed 3 



and more vaguely several still lower lignitic seams separ- 

 ated by rather uniform thicknesses of clay or tuff. 



The Tertiary materials have then, a maximum thickness 

 of 30 feet and a possible thickness of twice that amount. 

 Stratum No. 2 was recognized as probablv a tuff or ash 

 and stratum No. 4 appeared to be a clay. When studied in 

 the laboratory hand specimens of the former appeared so 

 light that they were carefully examined for diatoms without 

 positive result. They were, however, seen to consist of tiny 

 needles and angular particles of an isotropic material which 

 is obviously volcanic glass, and similar volcanic material 



