﻿Hatcher 
  — 
  Sedimentary 
  Hocks 
  of 
  Southern 
  Patagonia. 
  97 
  

  

  Toward 
  the 
  close 
  of 
  the 
  Eocene 
  there 
  began 
  over 
  southern 
  

   Patagonia 
  a 
  period 
  of 
  subsidence, 
  sufficient 
  to 
  bring 
  most 
  of 
  

   that 
  region 
  beneath 
  the 
  surface 
  of 
  a 
  shallow 
  sea. 
  Land 
  areas 
  

   continued 
  to 
  exist, 
  however, 
  along 
  the 
  Andes 
  and 
  an 
  important 
  

   land 
  mass 
  also 
  extended 
  over 
  what 
  is 
  now 
  the 
  central 
  interior 
  

   plains 
  region, 
  to 
  the 
  eastward 
  of 
  Lakes 
  Pneyrredon 
  and 
  

   Buenos 
  Ayres. 
  This 
  land 
  mass 
  was 
  perhaps 
  connected 
  with 
  

   the 
  continental 
  land 
  mass 
  to 
  the 
  northward. 
  From 
  the 
  com- 
  

   mencement 
  of 
  this 
  late 
  Eocene 
  subsidence 
  until 
  the 
  middle 
  of 
  

   the 
  Miocene, 
  marine 
  conditions, 
  more 
  or 
  less 
  extensive, 
  pre- 
  

   vailed 
  continuously 
  over 
  portions 
  of 
  this 
  region. 
  Such 
  marine 
  

   conditions 
  would 
  progress 
  or 
  recede 
  as 
  the 
  rate 
  of 
  subsidence 
  

   exceeded, 
  equalled 
  or 
  fell 
  below 
  the 
  rate 
  of 
  sedimentation 
  

   constantly 
  going 
  on 
  over 
  the 
  bottom, 
  and 
  thus 
  there 
  was 
  laid 
  

   down 
  over 
  this 
  region 
  a 
  series 
  of 
  deposits 
  of 
  marine 
  and 
  

   freshwater 
  or 
  aeolian 
  origin, 
  frequently 
  interstratified, 
  espec- 
  

   ially 
  about 
  the 
  shores 
  of 
  the 
  land 
  masses. 
  Such 
  marine 
  

   deposits 
  are 
  characterized 
  everywhere 
  by 
  abundant 
  remains 
  of 
  

   marine 
  invertebrates 
  of 
  shallow 
  water 
  forms 
  ; 
  while 
  the 
  lacus- 
  

   trine 
  and 
  aeolian 
  deposits, 
  though 
  less 
  rich 
  in 
  fossil 
  remains, 
  

   contain 
  the 
  bones 
  and 
  teeth 
  of 
  the 
  animals 
  inhabiting 
  the 
  

   lands 
  adjacent 
  to 
  or 
  over 
  which 
  they 
  were 
  deposited. 
  

  

  Eocene 
  and 
  Oligocene. 
  

  

  Magellanian 
  Series. 
  — 
  This 
  late 
  Eocene 
  subsidence 
  com- 
  

   menced 
  over 
  the 
  southern 
  regions 
  and 
  gradually 
  extended 
  

   northward. 
  In 
  the 
  vicinity 
  of 
  Punta 
  Arenas 
  there 
  are 
  repre- 
  

   sented 
  several 
  hundred 
  feet 
  of 
  marine 
  Tertiary 
  deposits 
  

   containing 
  a 
  marine 
  fauna 
  quite 
  distinct 
  and 
  of 
  decidedly 
  

   older 
  age 
  than 
  any 
  of 
  the 
  marine 
  Tertiary 
  deposits 
  known 
  

   from 
  the 
  Atlantic 
  coast 
  region 
  farther 
  north. 
  These 
  marine 
  

   deposits 
  have 
  been 
  named 
  by 
  Dr. 
  Ortmann 
  the 
  Magellanian 
  

   beds 
  and 
  a 
  brief 
  description 
  has 
  been 
  given 
  by 
  that 
  author 
  of 
  

   the 
  various 
  species 
  of 
  marine 
  invertebrates 
  collected 
  in 
  them 
  

   by 
  the 
  writer. 
  

  

  The 
  type 
  locality 
  for 
  the 
  Magellanian 
  beds 
  may 
  be 
  con- 
  

   sidered 
  to 
  be 
  the 
  bluffs 
  of 
  the 
  Rio 
  de 
  las 
  Minas 
  (Mines 
  Piver 
  

   on 
  the 
  map) 
  that 
  flows 
  through 
  the 
  town 
  of 
  Punta 
  Arenas 
  and 
  

   empties 
  into 
  the 
  Strait 
  of 
  Magellan. 
  These 
  beds 
  are 
  especially 
  

   well 
  represented 
  and 
  extensively 
  exposed 
  on 
  the 
  left 
  bank 
  of 
  

   that 
  stream 
  from 
  the 
  coal 
  mines 
  located 
  about 
  five 
  miles 
  above 
  

   the 
  town 
  to 
  a 
  point 
  some 
  three 
  miles 
  lower 
  down 
  where 
  the 
  

   stream 
  emerges 
  from 
  the 
  canon 
  onto 
  the 
  level 
  plain 
  that 
  

   extends 
  from 
  the 
  foot 
  of 
  the 
  hills 
  to 
  the 
  beach 
  north 
  of 
  the 
  

   town. 
  The 
  Pio 
  de 
  las 
  Minas 
  has 
  its 
  source 
  in 
  the 
  low 
  range 
  

   of 
  mountains 
  or 
  hills 
  separating 
  the 
  Magellan 
  Strait 
  from 
  

  

  