﻿H. 
  E. 
  Gregory 
  — 
  La 
  Paz 
  (Bolivia) 
  Gorge. 
  149 
  

  

  granite 
  bowlders 
  to 
  the 
  Cordillera 
  Real 
  at 
  the 
  north, 
  the 
  quartz 
  

   to 
  the 
  same 
  area, 
  and 
  also 
  to 
  the 
  mountains 
  near 
  Viacha 
  and 
  

   Colquencha 
  to 
  the 
  west, 
  clays 
  to 
  the 
  Ramos 
  formation 
  (Terti- 
  

   ary?) 
  underlying 
  the 
  altiplano, 
  and 
  the 
  ash 
  to 
  the 
  Letania 
  

   mountains. 
  

  

  As 
  to 
  the 
  condition 
  of 
  deposition 
  of 
  these 
  deposits, 
  D'Or- 
  

   bigny 
  and 
  Forbes 
  appear 
  to 
  have 
  held 
  no 
  definite 
  views. 
  

   Evans- 
  expresses 
  the 
  opinion 
  that 
  "the 
  enormous 
  deposits 
  of 
  

   alluvium 
  . 
  . 
  . 
  represent 
  not 
  the 
  alluvium 
  of 
  a 
  lake, 
  but 
  the 
  

   iirfillings 
  of 
  a 
  longitudinal 
  valley." 
  Zundtf 
  speaks 
  of 
  the 
  ash 
  

   deposit 
  as 
  carried 
  by 
  wind, 
  dropped 
  into 
  a 
  lake 
  or 
  sea 
  and 
  

   spread 
  by 
  the 
  waves. 
  Minchin^: 
  speaks 
  of 
  lake 
  beds, 
  a 
  part 
  of 
  

   the 
  floor 
  of 
  ancient 
  Titicaca, 
  now 
  covered 
  by 
  glacial 
  gravels. 
  

   D'Arlach§ 
  speaks 
  of 
  floods 
  induced 
  by 
  earthquakes 
  which 
  cut 
  

   the 
  La 
  Paz 
  gorge 
  and 
  drained 
  an 
  interior 
  sea. 
  Posnansky|| 
  

   apparently 
  considers 
  the 
  base 
  of 
  the 
  La 
  Paz 
  beds 
  as 
  marine- 
  

   built, 
  the 
  upper 
  portion 
  deposited 
  in 
  an 
  ancient 
  sea 
  detached 
  

   from 
  the 
  Pacific 
  by 
  uplift. 
  Zundt, 
  whose 
  previous 
  views 
  

   involved 
  the 
  existence 
  of 
  a 
  salt 
  sea, 
  considers 
  the 
  deposits 
  in 
  

   the 
  La 
  Paz 
  gorge 
  as 
  lacustrine, 
  — 
  the 
  fillings 
  of 
  a 
  temporary 
  

   lake 
  formed 
  by 
  blocking 
  an 
  ancient 
  river 
  which 
  drained 
  the 
  

   interior 
  basin. 
  The 
  upper 
  end 
  of 
  the 
  La 
  Paz 
  gorge 
  is 
  believed 
  

   by 
  this 
  writer 
  to 
  have 
  been 
  excavated 
  by 
  glaciers. 
  Bowman^f 
  

   recognized 
  the 
  fluviatile 
  origin 
  of 
  the 
  La 
  Paz 
  beds, 
  but 
  in 
  

   speaking 
  of 
  the 
  deposits 
  as 
  "the 
  coarsest 
  alluvium, 
  the 
  sort 
  of 
  

   material 
  that 
  mountain 
  torrents 
  carry," 
  evidently 
  had 
  in 
  mind 
  

   the 
  upper 
  beds 
  of 
  the 
  section 
  and 
  the 
  material 
  forming 
  the 
  

   banks 
  of 
  the 
  present 
  stream, 
  rather 
  than 
  the 
  fine-textured, 
  

   stratified 
  deposits 
  to 
  the 
  west 
  and 
  south 
  of 
  the 
  city. 
  

  

  From 
  the 
  general 
  and 
  detailed 
  sections 
  described 
  and 
  figured 
  

   above 
  it 
  appears 
  that 
  the 
  deposits 
  which 
  line 
  the 
  La 
  Paz 
  gorge 
  

   are 
  in 
  no 
  way 
  typical 
  of 
  lacustrine 
  formations. 
  The 
  absence 
  

   of 
  continuous 
  beds 
  of 
  thinly 
  laid 
  clays, 
  silts 
  and 
  the 
  finest 
  

   sands 
  of 
  uniform 
  texture, 
  the 
  presence 
  of 
  cross-bedding 
  and 
  

   channeling 
  and 
  the 
  rapid 
  alternation 
  of 
  gravels 
  and 
  sands 
  both 
  

   horizontally 
  and 
  vertically 
  argue 
  against 
  deposition 
  in 
  the 
  quiet 
  

   waters 
  of 
  a 
  lake. 
  All 
  the 
  phenomena 
  disclosed 
  by 
  the 
  study 
  of 
  

   the 
  sections 
  may 
  be 
  accounted 
  for 
  on 
  the 
  theory 
  that 
  the 
  region 
  

   was 
  traversed 
  by 
  low 
  grade, 
  piedmont 
  streams. 
  Such 
  streams 
  

   with 
  a 
  shifting 
  net-work 
  of 
  distributaries 
  and 
  interlaced 
  chan- 
  

   nels 
  alternately 
  depositing 
  and 
  cutting 
  in 
  a 
  capricious 
  manner 
  

  

  *Geog. 
  Jour., 
  vol. 
  xxii, 
  pp. 
  634-35, 
  1903. 
  

  

  f 
  Loc. 
  cit, 
  1907. 
  

  

  i 
  Geog. 
  Jour. 
  vol. 
  xxxvi, 
  pp. 
  396-7, 
  1910. 
  

  

  § 
  Bol. 
  Oficina 
  National 
  de 
  Estadistica, 
  No. 
  64-66, 
  p. 
  756, 
  La 
  Paz, 
  1911. 
  

  

  || 
  Bol. 
  Oficina 
  National 
  de 
  Estadistiea, 
  No. 
  64-66, 
  pp. 
  689-702, 
  1911. 
  

  

  IT 
  This 
  Journal, 
  vol. 
  xxviii, 
  p. 
  400, 
  1909. 
  

  

  