﻿Related 
  Sedimentary 
  Surface 
  Forms. 
  269 
  

  

  the 
  existing 
  currents 
  and 
  oscillations. 
  Pure 
  muds 
  can 
  

   not 
  form 
  ripples 
  at 
  all. 
  

  

  2. 
  The 
  absence 
  of 
  tidal 
  currents, 
  that 
  is, 
  of 
  an 
  open 
  

   connection 
  with 
  the 
  ocean. 
  (Applies 
  to 
  current-ripples 
  

   only; 
  cf. 
  p. 
  243.) 
  

  

  3. 
  A 
  depth 
  too 
  great 
  in 
  proportion 
  to 
  the 
  area 
  of 
  the 
  

   water 
  body 
  to 
  allow 
  waves 
  and 
  drift 
  currents 
  to 
  touch 
  

   bottom. 
  (Cf. 
  p. 
  246.) 
  

  

  The 
  preservation 
  of 
  ripples 
  is 
  made 
  impossible 
  by 
  

  

  4. 
  The 
  absence 
  of 
  the 
  conditions 
  favorable 
  for 
  a 
  rapid 
  

   covering 
  of 
  the 
  ripples, 
  as 
  outlined 
  below. 
  

  

  5. 
  It 
  should 
  be 
  noted 
  especially 
  that 
  in 
  relatively 
  

   coarse 
  homogeneous 
  sediments, 
  coarse 
  sands 
  for 
  instance, 
  

   not 
  capable 
  of 
  being 
  carried 
  any 
  distance 
  in 
  suspension 
  

   and 
  covering 
  extensive 
  areas, 
  the 
  stirring 
  of 
  the 
  sedi- 
  

   ments 
  does 
  not 
  result 
  in 
  a 
  covering 
  of 
  the 
  ripples 
  formed. 
  

  

  Judging 
  from 
  these 
  points, 
  ripples 
  will 
  be 
  absent 
  from 
  

   (a) 
  sediments 
  deposited 
  in 
  a 
  landlocked 
  sea 
  or 
  lake 
  with 
  

   too 
  large 
  a 
  form 
  ratio 
  (points 
  2 
  and 
  3), 
  or, 
  if 
  the 
  form 
  

   ratio 
  were 
  small 
  enough 
  to 
  cause 
  the 
  action 
  of 
  waves 
  on 
  

   the 
  bottom, 
  with 
  sediment 
  too 
  coarse 
  or 
  too 
  fine 
  to 
  give 
  

   rise 
  to 
  ripples 
  (points 
  1 
  and 
  2). 
  

  

  (b) 
  Also 
  from 
  well 
  assorted, 
  coarse 
  sands 
  or 
  other 
  

   arenites, 
  accumulated 
  in 
  a 
  shallow 
  water 
  body, 
  with 
  or 
  

   without 
  strong 
  tidal 
  currents 
  and 
  waves, 
  distant 
  from 
  the 
  

   mouths 
  of 
  streams 
  and 
  of 
  coasts 
  with 
  sand-laden 
  winds 
  

   (points 
  4 
  and 
  5). 
  

  

  Xot 
  one 
  of 
  these 
  points, 
  on 
  the 
  other 
  hand, 
  applies 
  to 
  

   terrestrial 
  alluvial 
  deposits. 
  There 
  is 
  no 
  reason 
  why 
  

   ripples 
  of 
  practically 
  all 
  kinds 
  should 
  not 
  be 
  found 
  in 
  

   profusion 
  in 
  all 
  fluviatile 
  deposits, 
  especially 
  in 
  such 
  as 
  

   were 
  accumulated 
  under 
  more 
  or 
  less 
  arid 
  conditions, 
  

   with 
  clouds 
  of 
  wind-blown 
  silt 
  and 
  sand 
  settling 
  into 
  the 
  

   shifting 
  waters. 
  

  

  It 
  appears 
  to 
  be 
  very 
  doubtful, 
  however, 
  if 
  ripples 
  will 
  

   ordinarily 
  be 
  preserved 
  in 
  dune 
  sands, 
  in 
  view 
  of 
  

   point 
  5, 
  which 
  certainly 
  is 
  of 
  equal 
  importance 
  in 
  sub- 
  

   aerial 
  as 
  in 
  subaqueous 
  sediments. 
  In 
  my 
  own 
  observa- 
  

   tions 
  of 
  sections 
  of 
  recent 
  dunes, 
  limited 
  to 
  shore 
  dunes, 
  

   I 
  have 
  never 
  seen 
  ripples 
  preserved 
  in 
  the 
  sands, 
  and 
  they 
  

   are 
  not 
  mentioned 
  in 
  the 
  descriptions 
  of 
  such 
  typical 
  fos- 
  

   sil 
  dune 
  sands 
  as 
  the 
  Sylvania 
  sandstone. 
  67 
  

  

  University 
  of 
  Cincinnati, 
  

   Cincinnati, 
  Ohio. 
  

  

  67 
  Sherzer, 
  W. 
  H., 
  and 
  Grabau, 
  A. 
  W., 
  Michigan 
  Geological 
  and 
  Biological 
  

   Survey, 
  Geol. 
  Series, 
  1, 
  pp. 
  61-86, 
  1909. 
  

  

  