﻿Related 
  Sedimentary 
  Surface 
  Forms. 
  247 
  

  

  commonly 
  found 
  but 
  close 
  to 
  the 
  shore. 
  Within 
  half 
  a 
  

   meter 
  from 
  the 
  shore 
  they 
  disappear 
  at 
  depths 
  measuring 
  

   in 
  centimeters. 
  On 
  the 
  shores 
  of 
  Lake 
  Geneva, 
  Forel 
  

   observed 
  ripples 
  down 
  to 
  a 
  depth 
  of 
  nearly 
  9 
  meters, 
  

   which 
  can 
  represent 
  but 
  a 
  relatively 
  narrow 
  zone, 
  as 
  the 
  

   mean 
  depth 
  of 
  the 
  lake 
  is 
  154 
  m. 
  16 
  

  

  In 
  all 
  sediments 
  deposited 
  in 
  basin-shaped 
  depressions, 
  

   especially 
  in 
  smaller, 
  more 
  or 
  less 
  enclosed 
  arms 
  of 
  the 
  

   sea, 
  or 
  bays, 
  such 
  as 
  for 
  instance 
  the 
  sea 
  of 
  Azof, 
  or 
  in 
  

   lakes, 
  we 
  should 
  expect 
  to 
  find 
  the 
  ripples 
  restricted 
  to 
  a 
  

   relatively 
  narrow 
  marginal 
  zone, 
  because 
  of 
  too 
  large 
  a 
  

   form 
  ratio. 
  This 
  explains 
  why 
  lacustrine 
  sediments 
  

   ordinarily 
  do 
  not 
  show 
  any 
  ripples 
  at 
  all. 
  

  

  It 
  is 
  probable 
  that 
  a 
  compilation 
  of 
  numerous 
  observa- 
  

   tions 
  on 
  presence 
  or 
  absence 
  of 
  ripples 
  in 
  clastic 
  forma- 
  

   tions 
  in 
  favorable 
  cases 
  might 
  yield 
  positive 
  results 
  

   concerning 
  the 
  general 
  trend 
  of 
  the 
  shore 
  line. 
  Accord- 
  

   ing 
  to 
  Daly, 
  for 
  instance, 
  ripple 
  marks 
  are 
  absent 
  from 
  

   the 
  very 
  fine-grained 
  quartzites 
  of 
  the 
  Creston 
  formation 
  

   of 
  the 
  Purcell 
  Mountain 
  System, 
  while 
  ' 
  * 
  elsewhere 
  within 
  

   the 
  Boundary 
  belt 
  these 
  markings 
  were 
  found. 
  ' 
  nl 
  Cases 
  

   like 
  this 
  deserve 
  consideration 
  in 
  detailed 
  stratigraphic 
  

   studies. 
  The 
  stratigraphic 
  position 
  and 
  dimensions 
  of 
  

   the 
  ripples 
  of 
  many 
  formations 
  deserve 
  as 
  well 
  a 
  place 
  

   in 
  the 
  field 
  geologist's 
  notebook 
  as 
  fossils. 
  

  

  (d) 
  There 
  are 
  two 
  observations 
  of 
  ripples 
  on 
  record, 
  

   which, 
  so 
  far 
  as 
  I 
  know, 
  seem 
  to 
  imply 
  true 
  shore 
  condi- 
  

   tions, 
  18 
  and 
  therefore 
  are 
  of 
  special 
  interest 
  to 
  the 
  paleo- 
  

   geographer. 
  Dawson 
  19 
  figures 
  a 
  " 
  rippled 
  surface 
  in 
  

   Potsdam 
  Sandstone 
  with 
  marks 
  of 
  worms 
  or 
  molluscs 
  

   arranged 
  in 
  the 
  hollows 
  of 
  the 
  ripples. 
  The 
  marks 
  are 
  

   simple 
  trails, 
  of 
  that 
  curious 
  circular 
  or 
  chain-like 
  form 
  

   sometimes 
  observed, 
  and 
  seem 
  to 
  have 
  been 
  made 
  by 
  

   animals 
  creeping 
  in 
  the 
  furrows 
  between 
  the 
  ridges 
  of 
  the 
  

   ripple-marks." 
  It 
  is 
  of 
  no 
  little 
  interest 
  to 
  see 
  very 
  

   similar 
  if 
  not 
  identical 
  tracks 
  confined 
  in 
  the 
  same 
  way 
  

   to 
  the 
  troughs 
  of 
  ripples 
  figured 
  by 
  Stuchlik 
  (1906; 
  table 
  

   8, 
  fig. 
  3) 
  from 
  the 
  Oligocene 
  Molasse 
  Sandstone 
  of 
  Lech- 
  

   bruck 
  (foot 
  of 
  Bavarian 
  Alps). 
  The 
  conclusion 
  seems 
  

   to 
  be 
  unavoidable 
  that 
  the 
  animals 
  were 
  concentrated 
  in 
  

  

  18 
  A. 
  Supan, 
  Grundzuege 
  d. 
  phys. 
  Erdkunde, 
  1911, 
  p. 
  753. 
  

   17 
  Geol. 
  Survey, 
  Canada, 
  Memoir 
  38, 
  Pt. 
  I, 
  p. 
  123, 
  1912. 
  

   18 
  Not 
  necessarily 
  marine, 
  of 
  course. 
  

  

  1!) 
  J. 
  W. 
  Dawson, 
  On 
  burrows 
  and 
  tracks, 
  etc., 
  Q. 
  J. 
  Geol. 
  Soc, 
  London, 
  

   vol. 
  46, 
  p. 
  611, 
  fig. 
  14, 
  1890. 
  

  

  