﻿Hatcher 
  — 
  Sedimentary 
  Bocks 
  of 
  Southern 
  Patagonia. 
  107 
  

  

  difference 
  of 
  46 
  feet, 
  takes 
  place 
  along 
  the 
  bedding 
  plains. 
  

   Thus 
  the 
  same 
  stratum 
  frequently 
  forms 
  the 
  surface 
  over 
  con- 
  

   siderable 
  areas, 
  and 
  the 
  present 
  slope 
  of 
  the 
  beach 
  is 
  often 
  for 
  

   considerable 
  distances 
  precisely 
  that 
  of 
  the 
  inclination 
  of 
  the 
  

   beds. 
  Consequently 
  in 
  this 
  region 
  when 
  a 
  particularly 
  rich 
  

   fossiliferous 
  horizon 
  is 
  found 
  in 
  the 
  bluff, 
  it 
  will 
  appear 
  at 
  its 
  

   proper 
  place 
  on 
  the 
  beach 
  owing 
  to 
  the 
  southeasterly 
  dip 
  of 
  

   the 
  beds, 
  and 
  will 
  form 
  the 
  surface 
  over 
  a 
  considerable 
  area 
  

   often 
  two 
  or 
  three 
  miles 
  in 
  extent, 
  each 
  bedding 
  plane 
  appear- 
  

   ing 
  successively 
  as 
  the 
  present 
  surface 
  of 
  the 
  beach, 
  exposed 
  

   to 
  view 
  only 
  at 
  low 
  tide. 
  When 
  such 
  localities 
  were 
  met 
  with 
  

   they 
  were 
  found 
  to 
  be 
  extremely 
  rich 
  in 
  fossils, 
  and 
  it 
  was 
  

   frequently 
  possible 
  while 
  standing 
  in 
  one 
  position 
  to 
  count 
  a 
  

   dozen 
  or 
  more 
  skeletons, 
  varying 
  in 
  completeness 
  according 
  as 
  

   they 
  had 
  been 
  more 
  or 
  less 
  uncovered 
  and 
  washed 
  away 
  by 
  the 
  

   tides. 
  Not 
  only 
  were 
  the 
  skeletons 
  of 
  these 
  animals 
  to 
  be 
  

   found, 
  but 
  in 
  several 
  places 
  their 
  fossil 
  footprints 
  were 
  observed, 
  

   and 
  owing 
  to 
  the 
  peculiarly 
  favorable 
  erosive 
  action 
  which 
  

   prevails 
  here, 
  series 
  of 
  such 
  footprints 
  were 
  occasionally 
  seen 
  

   extending 
  for 
  upwards 
  of 
  100 
  feet, 
  each 
  track 
  distinctly 
  

   impressed 
  so 
  that 
  it 
  would 
  have 
  been 
  possible 
  to 
  count 
  the 
  

   number 
  of 
  steps 
  taken 
  in 
  covering 
  a 
  given 
  distance 
  and 
  to 
  

   measure 
  the 
  exact 
  stride 
  of 
  the 
  animal. 
  All 
  these 
  conditions 
  

   taken 
  together 
  bear 
  conclusive 
  evidence, 
  it 
  seems 
  to 
  me, 
  that 
  

   the 
  skeletons 
  belong 
  to 
  the 
  same 
  animals 
  that 
  made 
  the 
  foot- 
  

   prints 
  and 
  therefore 
  that 
  these 
  animals 
  inhabited 
  this 
  very 
  

   region 
  during 
  the 
  time 
  when 
  the 
  sediments 
  now 
  forming 
  the 
  

   rocks 
  were 
  being 
  accumulated 
  in 
  the 
  bottoms 
  and 
  over 
  the 
  

   flood 
  plains 
  of 
  the 
  swamps, 
  small 
  lakes, 
  and 
  tributary 
  streams 
  

   which 
  existed 
  here. 
  Periodical 
  variations 
  in 
  the 
  amount 
  of 
  

   moisture, 
  together 
  with 
  other 
  conditions, 
  would 
  perhaps 
  account 
  

   for 
  the 
  lack 
  of 
  invertebrate 
  remains. 
  

  

  Since 
  the 
  Santa 
  Cruz 
  beds 
  conformably 
  overlie 
  the 
  Patago- 
  

   nian 
  beds, 
  which 
  have 
  been 
  shown 
  to 
  belong 
  to 
  the 
  Upper 
  Oli- 
  

   gocene 
  and 
  Lower 
  Miocene, 
  the 
  Santa 
  Cruz 
  beds 
  must 
  therefore 
  

   belong 
  to 
  the 
  Middle 
  and 
  Upper 
  Miocene. 
  This 
  stratigraphical 
  

   evidence 
  of 
  the 
  age 
  of 
  these 
  beds 
  is 
  strongly 
  supported 
  by 
  the 
  

   paleontological 
  evidences 
  afforded 
  by 
  the 
  mammalian 
  remains 
  

   found 
  in 
  them. 
  The 
  highly 
  specialized 
  character 
  of 
  most 
  of 
  

   the 
  genera 
  can 
  hardly 
  be 
  taken 
  to 
  indicate 
  a 
  greater 
  antiquity 
  

   for 
  any 
  of 
  the 
  strata 
  than 
  Middle 
  Miocene. 
  

  

  Cape 
  Fairweather 
  beds.— 
  The 
  close 
  of 
  the 
  Miocene 
  was 
  

   marked 
  by 
  a 
  general 
  subsidence, 
  so 
  that 
  the 
  sea 
  again 
  had 
  access 
  

   to 
  this 
  region, 
  and 
  during 
  Pliocene 
  times 
  marine 
  conditions 
  

   prevailed 
  here, 
  resulting 
  in 
  the 
  deposition 
  of 
  a 
  series 
  of 
  deposits 
  

   with 
  a 
  marine 
  invertebrate 
  fauna 
  which 
  originally 
  covered 
  

   almost 
  the 
  entire 
  region, 
  but 
  has 
  since 
  been 
  mostly 
  removed 
  

   and 
  now 
  appears 
  over 
  limited 
  and 
  widely 
  separated 
  areas, 
  rest- 
  

  

  