﻿268 
  Bucher 
  — 
  Origin 
  of 
  Ripples, 
  and 
  

  

  such 
  as 
  tropical 
  cyclones 
  or, 
  more 
  probably, 
  those 
  of 
  

   intermediate 
  latitudes. 
  

  

  In 
  the 
  paper 
  referred 
  to, 
  considerable 
  emphasis 
  is 
  laid 
  

   on 
  a 
  sufficient 
  rate 
  of 
  sedimentation 
  as 
  the 
  chief 
  condition 
  

   for 
  a 
  preservation 
  of 
  the 
  ripples 
  formed. 
  The 
  discus- 
  

   sion, 
  which 
  involves 
  an 
  interpretation 
  of 
  the 
  origin 
  of 
  

   the 
  more 
  or 
  less 
  rhythmic 
  repetition 
  of 
  shales 
  and 
  lime- 
  

   stones 
  in 
  the 
  Upper 
  Ordovician 
  of 
  the 
  Cincinnati 
  Anti- 
  

   cline, 
  can 
  not 
  be 
  given 
  here. 
  

  

  The 
  fact 
  that 
  at 
  least 
  four 
  independent 
  factors 
  had 
  to 
  

   combine 
  for 
  the 
  production 
  of 
  these 
  ripples, 
  namely 
  suffi- 
  

   ciently 
  strong 
  tidal 
  action, 
  frequent 
  periods 
  of 
  strong 
  

   storms, 
  a 
  relatively 
  small 
  depth 
  of 
  water, 
  and 
  a 
  sufficient 
  

   rate 
  of 
  sedimentation 
  to 
  insure 
  their 
  preservation, 
  

   explains 
  why 
  such 
  large 
  current-ripples 
  are 
  not 
  found 
  

   commonly 
  over 
  wide 
  areas 
  in 
  the 
  sedimentary 
  record 
  of 
  

   other 
  seas. 
  

  

  The 
  large 
  ripples 
  produced 
  along 
  the 
  shores 
  by 
  ordi- 
  

   nary 
  tidal 
  currents, 
  also 
  have 
  much 
  poorer 
  chances 
  for 
  

   preservation 
  than 
  smaller 
  ripples, 
  because 
  they 
  require 
  

   a 
  thicker 
  cover 
  in 
  order 
  to 
  be 
  preserved. 
  This 
  explains 
  

   their 
  scarcity 
  in 
  shore 
  deposits. 
  The 
  same 
  is 
  true 
  of 
  

   fluviatile 
  ripples. 
  

  

  In 
  view 
  of 
  the 
  fact 
  that 
  strong 
  tidal 
  currents 
  are 
  found 
  

   only 
  in 
  waterbodies 
  which 
  are 
  in 
  direct 
  open 
  connection 
  

   with 
  the 
  sea 
  and 
  not 
  in 
  landlocked 
  seas, 
  whether 
  mediter- 
  

   raneous 
  or 
  epicontinental 
  seas, 
  the 
  presence 
  of 
  para-rip- 
  

   ples 
  in 
  marine 
  deposits 
  ranging 
  in 
  age 
  from 
  the 
  Lower 
  

   Ordovician 
  to 
  the 
  Comanchean, 
  all 
  from 
  the 
  United 
  States 
  

   west 
  of 
  "Appalachia," 
  is 
  of 
  fundamental 
  interest. 
  

   Many 
  more 
  will 
  be 
  recorded 
  66 
  and 
  will 
  doubtless 
  furnish 
  

   valuable 
  checks 
  on 
  many 
  lines 
  that 
  will 
  be 
  drawn 
  on 
  

   future 
  paleogeographic 
  maps. 
  

  

  IV. 
  General 
  absence 
  of 
  Eipples 
  in 
  certain 
  Formations. 
  

  

  One 
  question 
  remains 
  to 
  be 
  answered 
  : 
  Why 
  are 
  ripples 
  

   entirely 
  absent 
  from 
  certain 
  formations, 
  while 
  they 
  are 
  a 
  

   conspicuous 
  feature 
  throughout 
  others? 
  

  

  The 
  formation 
  of 
  ripples 
  is 
  prevented 
  by: 
  

  

  1. 
  Sediments 
  too 
  coarse 
  or 
  too 
  fine 
  in 
  proportion 
  to 
  

  

  ' 
  Every 
  occurrence 
  of 
  such 
  large 
  ripples 
  deserves 
  publication. 
  The 
  wave- 
  

   length, 
  amplitude, 
  degree 
  of 
  asymmetry, 
  direction 
  of 
  trend 
  and 
  a 
  detailed 
  

   account 
  of 
  the 
  texture 
  of 
  the 
  sediment 
  should 
  be 
  given 
  besides 
  detailed 
  

   topographic 
  and 
  stratigraphic 
  location. 
  

  

  