﻿98 
  Hatcher 
  — 
  Sedimentary 
  Rocks 
  of 
  Southern 
  Patagonia. 
  

  

  Otwaj 
  Water 
  and 
  forming 
  the 
  northern 
  portion 
  of 
  the 
  Bruns- 
  

   wick 
  peninsula, 
  the 
  southernmost 
  point 
  of 
  the 
  mainland 
  of 
  South 
  

   America. 
  The 
  river 
  has 
  a 
  nearly 
  east 
  and 
  west 
  course, 
  and 
  

   throughout 
  its 
  entire 
  length 
  the 
  bluffs 
  on 
  either 
  side 
  of 
  the 
  

   stream 
  are 
  composed 
  of 
  sedimentary 
  deposits 
  of 
  varying 
  age 
  

   from 
  Upper 
  Eocene 
  to 
  Pliocene, 
  excepting 
  certain 
  bowlder 
  

   deposits 
  on 
  the 
  top 
  of 
  the 
  mountains 
  and 
  other 
  loess 
  deposits 
  

   in 
  the 
  valley, 
  both 
  of 
  which 
  are 
  unfossiliferous 
  and 
  evi- 
  

   dently 
  of 
  Pleistocene 
  age. 
  

  

  Ascending 
  the 
  river 
  from 
  Punta 
  Arenas, 
  the 
  Magellanian 
  

   beds 
  are 
  first 
  seen 
  just 
  where 
  the 
  stream 
  emerges 
  from 
  the 
  

   mountains 
  about 
  two 
  miles 
  above 
  the 
  town. 
  At 
  a 
  short 
  dis- 
  

   tance 
  above 
  this 
  point 
  a 
  more 
  important 
  exposure 
  may 
  be 
  seen 
  

   on 
  the 
  left 
  bank 
  of 
  the 
  stream 
  where 
  the 
  axis 
  of 
  a 
  very 
  gentle 
  

   anticline 
  is 
  passed. 
  From 
  the 
  axis 
  of 
  this 
  anticline 
  the 
  strata 
  

   on 
  one 
  side 
  dip 
  gently 
  to 
  the 
  eastward 
  or 
  down 
  stream 
  and 
  

   soon 
  successively 
  disappear 
  beneath 
  the 
  bed 
  of 
  the 
  stream, 
  

   while 
  on 
  the 
  other 
  side 
  they 
  dip 
  to 
  the 
  westward 
  or 
  up 
  stream 
  

   at 
  an 
  angle 
  of 
  perhaps 
  five 
  degrees. 
  This 
  westward 
  inclina- 
  

   tion 
  of 
  the 
  strata 
  is 
  continuous 
  from 
  the 
  axis 
  of 
  the 
  anticline 
  

   to 
  the 
  source 
  of 
  the 
  river 
  except 
  where 
  affected 
  by 
  some 
  

   local 
  fault 
  or 
  landslide, 
  as 
  frequently 
  happens 
  above 
  the 
  coal 
  

   mines 
  and 
  therefore 
  in 
  the 
  beds 
  above 
  the 
  Magellanian 
  beds. 
  

   No 
  such 
  faults 
  were 
  observed 
  in 
  the 
  Magellanian 
  beds 
  below 
  

   the 
  mines. 
  

  

  In 
  the 
  bluff 
  at 
  the 
  anticline, 
  a 
  few 
  feet 
  above 
  the 
  bed 
  of 
  the 
  

   stream, 
  there 
  is 
  a 
  layer 
  with 
  numerous 
  flattened 
  concretions 
  

   frequently 
  a 
  foot 
  or 
  two 
  in 
  diameter 
  and 
  of 
  a 
  light 
  gray 
  color, 
  

   with 
  fairly 
  abundant 
  leaf 
  impressions, 
  belonging 
  principally 
  to 
  

   the 
  genus 
  Fagus. 
  Some 
  fifty 
  feet 
  higher 
  up 
  in 
  the 
  bluff 
  

   another 
  concretionary 
  layer 
  is 
  encountered 
  containing 
  in 
  great 
  

   abundance 
  the 
  remains 
  of 
  marine 
  invertebrates. 
  In 
  ascend- 
  

   ing 
  the 
  river 
  some 
  two 
  or 
  three 
  miles 
  until 
  the 
  coal 
  mines 
  are 
  

   reached, 
  several 
  hundred 
  feet 
  of 
  strata 
  are 
  passed 
  through 
  

   containing 
  numerous 
  fossil-bearing 
  layers. 
  Two 
  such 
  layers, 
  

   each 
  about 
  ten 
  or 
  twenty 
  feet 
  thick, 
  are 
  especially 
  prominent, 
  

   appearing 
  as 
  bold 
  projecting 
  ledges 
  due 
  to 
  the 
  harder 
  nature 
  of 
  

   the 
  rocks 
  composing 
  them, 
  and 
  made 
  up 
  largely 
  of 
  the 
  shells 
  

   of 
  various 
  species 
  of 
  mollusca. 
  

  

  Dr. 
  A. 
  E. 
  Ortmann, 
  who 
  has 
  studied 
  the 
  invertebrate 
  Collec- 
  

   tions 
  from 
  these 
  beds, 
  has 
  decided 
  that 
  they 
  are 
  not 
  only 
  quite 
  

   distinct 
  from 
  the 
  faunas 
  of 
  the 
  Patagonian 
  and 
  Supra-Pala- 
  

   gonian 
  beds 
  of 
  the 
  Atlantic 
  coast 
  farther 
  north, 
  but 
  also 
  that 
  

   they 
  differ 
  entirely 
  from 
  the 
  invertebrate 
  faunas 
  of 
  the 
  marine 
  

   beds 
  overlying 
  the 
  coal 
  beds 
  at 
  this 
  locality. 
  He 
  considers 
  

   the 
  fauna 
  of 
  the 
  Magellanian 
  beds 
  as 
  indicative 
  of 
  a 
  decidedly 
  

   greater 
  age 
  for 
  these 
  beds 
  than 
  should 
  be 
  accorded 
  to 
  the 
  Pata- 
  

  

  