﻿148 
  

  

  H. 
  E. 
  Gregory 
  — 
  La 
  Paz 
  (Bolivia) 
  Gorge. 
  

  

  " 
  20 
  to 
  30 
  feet 
  in 
  thickness," 
  Forbes 
  considered 
  as 
  part 
  of 
  a 
  

   wide-spread 
  " 
  diluvial 
  formation," 
  occupying 
  a 
  basin 
  between 
  

   the 
  Silurian 
  rocks 
  of 
  the 
  high 
  Andes 
  and 
  the 
  low 
  Devonian 
  

   hills 
  to 
  the 
  west, 
  and 
  believed 
  the 
  impure 
  lignite 
  to 
  be 
  an 
  

   extension 
  of 
  the 
  carbonaceous 
  strata 
  exposed 
  at 
  the 
  foot 
  of 
  

   Illimani 
  and 
  also 
  near 
  Poto-poto. 
  The 
  material 
  composing 
  

  

  Fig. 
  7. 
  

  

  — 
  If 
  i 
  \ 
  ' 
  '' 
  ' 
  _ 
  "^ 
  ° 
  Q 
  ° 
  ' 
  = 
  o"^- 
  

  

  >£> 
  .:».=> 
  

  

  Fig. 
  7. 
  Portion 
  of 
  gravel 
  lens 
  ; 
  extent 
  and 
  thickness 
  of 
  gravel 
  and 
  sand 
  

   and 
  orientation 
  of 
  cross-bedding 
  laminae 
  drawn 
  to 
  scale. 
  

  

  Fig. 
  

  

  a, 
  sand 
  with 
  irregularly 
  distributed 
  gravel, 
  b, 
  gravel 
  with 
  two 
  lenses 
  of 
  clay. 
  

  

  Fig. 
  8. 
  Section 
  on 
  line 
  of 
  Arica-La 
  Paz 
  railroad, 
  showing 
  contact 
  

   between 
  gravel 
  and 
  sand. 
  Drawn 
  to 
  scale. 
  

  

  these 
  beds 
  lias 
  its 
  source, 
  according 
  to 
  Forbes, 
  in 
  the 
  Silurian 
  

   strata 
  of 
  the 
  Cordillera 
  Real 
  ; 
  with 
  the 
  exception 
  of 
  the 
  vol- 
  

   canic 
  ash, 
  which 
  he 
  assumes 
  had 
  been 
  carried 
  by 
  streams 
  from 
  

   Achacachi 
  on 
  the 
  shores 
  of 
  Lake 
  Titicaca. 
  Zundt* 
  assigns 
  the 
  

  

  * 
  Appendix 
  to 
  Spanish 
  edition 
  of 
  D'Orbigny, 
  La 
  Paz, 
  1907. 
  

  

  