﻿Appalachian 
  Geosyncline. 
  437 
  

  

  development 
  of 
  continental 
  as 
  contrasted 
  to 
  littoral 
  and 
  marine 
  

   deposits 
  and 
  the 
  criteria 
  which 
  may 
  thence 
  be 
  drawn 
  for 
  sepa- 
  

   rating 
  the 
  snbaerial 
  from 
  the 
  subaqueous 
  beds 
  of 
  deltas. 
  This 
  

   article 
  in 
  fact 
  is 
  a 
  logical 
  sequence 
  of 
  earlier 
  papers, 
  and 
  here 
  

   only 
  a 
  summary 
  of 
  the 
  more 
  important 
  criteria 
  will 
  be 
  given.* 
  

  

  Many 
  features 
  from 
  which 
  an 
  observer 
  ma} 
  7 
  gain 
  an 
  impres- 
  

   sion 
  as 
  to 
  the 
  mode 
  of 
  origin 
  of 
  a 
  deposit 
  are 
  really 
  not 
  definite 
  

   proofs. 
  Thus 
  ripple-marked, 
  cross-bedded, 
  and 
  fossil 
  -barren 
  

   deposits 
  may 
  be 
  developed 
  either 
  beneath 
  a 
  permanent 
  water 
  

   cover 
  or 
  upon 
  river 
  plains, 
  though 
  doubtless 
  the 
  quantity 
  and 
  

   quality 
  of 
  their 
  development 
  differ 
  in 
  the 
  two 
  cases. 
  

  

  fled 
  beds 
  have 
  been 
  regarded 
  b} 
  7 
  souie 
  because 
  of 
  their 
  color 
  

   as 
  evidences 
  of 
  terrestrial 
  deposition 
  ; 
  by 
  others, 
  of 
  seas 
  barren 
  

   of 
  life. 
  Again, 
  they 
  have 
  been 
  cited 
  as 
  indications 
  of 
  a 
  deeply 
  

   decayed 
  regolith, 
  of 
  a 
  humid 
  climate, 
  or 
  of 
  aridity. 
  The 
  

   present 
  writer 
  holds 
  that 
  redness 
  in 
  rocks 
  may 
  in 
  fact 
  accom- 
  

   pany 
  any 
  of 
  these 
  conditions 
  and 
  is 
  not 
  therefore 
  a 
  criterion 
  

   by 
  itself 
  of 
  anyone. 
  

  

  Mud 
  cracks 
  and 
  conglomerates 
  have 
  been 
  cited 
  usually 
  as 
  

   evidences 
  of 
  ancient 
  tidal 
  flats 
  and 
  beaches, 
  but 
  are 
  now 
  

   observed 
  to 
  occur 
  chiefly 
  in 
  river 
  deposits 
  of 
  continental 
  inte- 
  

   riors. 
  Those 
  formed 
  in 
  the 
  littoral 
  zone 
  furthermore 
  except 
  

   on 
  the 
  fronts 
  of 
  deltas 
  are 
  rather 
  unfavorably 
  situated 
  for 
  geo- 
  

   logical 
  preservation, 
  and 
  are 
  to 
  be 
  distinguished 
  by 
  associations 
  

   which 
  are 
  commonly 
  absent 
  in 
  ancient 
  examples. 
  Thus 
  it 
  is 
  

   clear 
  that 
  it 
  is 
  the 
  character, 
  the 
  quantitative 
  development, 
  

   and 
  associations 
  of 
  the 
  stratigraphic 
  features 
  which 
  are 
  signifi- 
  

   cant 
  rather 
  than 
  their 
  mere 
  occurrence. 
  

  

  In 
  general, 
  traditional 
  criteria 
  are 
  liable 
  to 
  lead 
  into 
  error, 
  

   because 
  they 
  become 
  accepted 
  as 
  axioms 
  and 
  are 
  applied 
  with- 
  

   out 
  further 
  thought. 
  They 
  lag 
  behind 
  the 
  development 
  of 
  a 
  

   science, 
  whereas 
  the 
  very 
  word 
  ' 
  research 
  ' 
  implies 
  the 
  neces- 
  

   sity 
  of 
  continually 
  testing 
  the 
  correspondence 
  of 
  the 
  images 
  of 
  

   science 
  with 
  nature. 
  

  

  Attention 
  may 
  now 
  be 
  turned 
  to 
  what 
  may 
  be 
  regarded 
  in 
  

   the 
  present 
  state 
  of 
  knowledge 
  as 
  fairly 
  definite 
  criteria 
  which 
  

   will 
  be 
  of 
  use 
  in 
  discussing 
  the 
  origin 
  of 
  the 
  Catskill 
  and 
  asso- 
  

   ciated 
  formations. 
  

  

  Marine 
  fossils 
  on 
  the 
  one 
  hand, 
  or 
  abundance 
  of 
  land 
  fossils 
  

   on 
  the 
  other, 
  furnish 
  of 
  course 
  clear 
  cases 
  save 
  in 
  those 
  minor 
  

   instances 
  where 
  the 
  blowing 
  inland 
  of 
  sand 
  from 
  beaches 
  or 
  

   the 
  reworking 
  by 
  rivers 
  of 
  the 
  mud 
  of 
  an 
  abandoned 
  sea 
  flat 
  

   may 
  have 
  mixed 
  small 
  marine 
  fossils 
  into 
  closely 
  related 
  land 
  

  

  * 
  Eelative 
  geological 
  importance 
  of 
  continental, 
  littoral, 
  and 
  marine 
  sedi- 
  

   mentation. 
  Jonr. 
  Geol., 
  xiv, 
  pp. 
  316-356, 
  430-457, 
  524-568, 
  1906. 
  

  

  Criteria 
  for 
  the 
  recognition 
  of 
  ancient 
  delta 
  deposits. 
  Geol. 
  Soc. 
  Am., 
  

   Bull., 
  xxiii, 
  pp. 
  377-446, 
  1912. 
  

  

  