﻿92 
  Hatcher 
  — 
  Sedimentary 
  Hocks 
  of 
  Southern 
  Patagonia. 
  

  

  and 
  shown 
  to 
  Dr. 
  Ameghino. 
  This 
  horizon, 
  as 
  has 
  already 
  

   been 
  shown, 
  belongs 
  to 
  the 
  Cretaceous 
  and 
  not 
  to 
  the 
  Jurassic 
  * 
  

   It 
  seems 
  probable 
  that 
  Dr. 
  Ameghino 
  has 
  in 
  each 
  instance, 
  as 
  

   is 
  evident 
  in 
  this 
  one, 
  when 
  dealing 
  with 
  these 
  marine 
  Meso- 
  

   zoic 
  horizons, 
  based 
  his 
  remarks 
  on 
  the 
  discoveries 
  and 
  observa- 
  

   tions 
  of 
  others 
  and 
  made 
  his 
  correlations 
  to 
  agree 
  with 
  his 
  

   own 
  preconceived 
  ideas 
  ; 
  instead 
  of 
  submitting 
  such 
  correla- 
  

   tions 
  to 
  and 
  abiding 
  by 
  the 
  judgment 
  of 
  specialists 
  in 
  Mesozoic 
  

   invertebrates. 
  

  

  Although 
  the 
  present 
  known 
  surface 
  distribution 
  of 
  the 
  

   rocks 
  of 
  the 
  Pueyrredon 
  Series 
  is 
  exceedingly 
  limited, 
  it 
  is 
  

   quite 
  probable 
  that 
  future 
  explorations 
  will 
  show 
  that 
  they 
  

   are 
  represented 
  in 
  a 
  more 
  or 
  less 
  continuous 
  series 
  of 
  out- 
  

   crops 
  extending 
  all 
  along 
  the 
  eastern 
  range 
  of 
  the 
  southern 
  

   Andes. 
  

  

  San 
  Martin 
  Series. 
  — 
  In 
  this 
  series 
  it 
  is 
  proposed 
  to 
  include 
  

   some 
  3,500 
  feet 
  of 
  Upper 
  Cretaceous 
  rocks, 
  for 
  the 
  most 
  part 
  

   well 
  represented 
  at 
  various 
  places 
  throughout 
  southern 
  Pata- 
  

   gonia 
  and 
  more 
  especially 
  in 
  the 
  region 
  lying 
  directly 
  east 
  of 
  

   Lake 
  San 
  Martin. 
  

  

  The 
  Areniscas 
  Abigarradas 
  beds. 
  — 
  These 
  beds, 
  also 
  fre- 
  

   quently 
  referred 
  to 
  as 
  the 
  Variegated 
  Sandstones, 
  lie 
  at 
  the 
  base 
  

   of 
  the 
  San 
  Martin 
  series. 
  They 
  are 
  well 
  represented 
  in 
  the 
  

   bluffs 
  along 
  the 
  south 
  shore 
  of 
  the 
  east 
  end 
  of 
  Lake 
  Pueyrredon 
  

   and 
  of 
  the 
  deep 
  valley 
  extending 
  eastward 
  from 
  that 
  lake. 
  In 
  

   the 
  canon 
  of 
  Rio 
  Tarde 
  they 
  may 
  be 
  seen 
  in 
  a 
  series 
  of 
  hard, 
  

   well 
  stratified 
  sandstones 
  1,350 
  feet 
  thick, 
  overlying 
  the 
  Upper 
  

   Conglomerates 
  of 
  the 
  Pueyrredon 
  Series, 
  with 
  which 
  they 
  

   appear 
  slightly 
  unconformable. 
  They 
  are 
  usually 
  fine-grained 
  

   and 
  of 
  varying 
  colors, 
  with 
  light 
  pinks 
  and 
  pale 
  greens 
  pre- 
  

   dominating. 
  They 
  are 
  exceedingly 
  barren 
  of 
  fossils, 
  a 
  some- 
  

   what 
  careful 
  search 
  at 
  this 
  and 
  several 
  other 
  localities 
  being 
  

   rewarded 
  by 
  the 
  discovery 
  of 
  only 
  a 
  few 
  imperfect 
  and 
  unchar- 
  

   acteristic 
  plant 
  remains. 
  

  

  The 
  rocks 
  of 
  the 
  Areniscas 
  Abigarradas 
  beds 
  have 
  a 
  much 
  

   more 
  extensive 
  surface 
  distribution 
  than 
  any 
  of 
  the 
  other 
  

   Cretaceous 
  deposits 
  of 
  southern 
  Patagonia. 
  They 
  appear 
  

   over 
  large 
  areas 
  all 
  along 
  the 
  eastern 
  base 
  of 
  the 
  Andes 
  and 
  

   are 
  known 
  to 
  cover 
  a 
  considerable 
  portion 
  of 
  the 
  interior 
  

   plains 
  region 
  lying 
  to 
  the 
  eastward 
  of 
  Lakes 
  Pueyrredon 
  and 
  

   Buenos 
  Ayres, 
  extending 
  even 
  to 
  the 
  Atlantic 
  coast, 
  as 
  may 
  be 
  

   observed 
  at 
  Port 
  Desire. 
  They 
  also 
  outcrop 
  at 
  intervals 
  in 
  the 
  

   valley 
  of 
  San 
  Julian, 
  which 
  extends 
  inland 
  for 
  many 
  miles 
  from 
  

   the 
  head 
  of 
  the 
  present 
  bay 
  of 
  the 
  same 
  name. 
  

  

  Owing 
  to 
  the 
  great 
  thickness 
  and 
  uniform 
  hardness 
  of 
  these 
  

   sandstones 
  as 
  compared 
  with 
  most 
  of 
  the 
  other 
  sedimentary 
  

   deposits 
  of 
  southern 
  Patagonia, 
  wherever 
  found, 
  they 
  form 
  

  

  