﻿NIAGARA 
  FALLS 
  AND 
  VICINITY 
  

  

  41 
  

  

  of 
  the 
  cuesta, 
  and 
  ultimately 
  prolong-ed 
  these 
  gullies 
  into 
  gorges, 
  

   and 
  carried 
  the 
  drainage 
  into 
  the 
  subsequent 
  streams. 
  Streams 
  of 
  

   this 
  type, 
  which 
  have 
  their 
  representatives 
  in 
  all 
  coastal 
  plain 
  

   regions, 
  have 
  been 
  called 
  obsequent 
  streams,^ 
  their 
  direction 
  of 
  flow 
  

   being 
  opposite 
  to 
  that 
  of 
  the 
  consequent 
  streams. 
  The 
  following 
  

   diagram 
  (fig. 
  4) 
  illustrates 
  this 
  type 
  of 
  a 
  stream 
  and 
  its 
  relation 
  to 
  the 
  

   subsequent 
  and 
  consequent 
  streams. 
  To 
  this 
  type 
  of 
  stream 
  belongs 
  

   the 
  ancient 
  St 
  Davids 
  gorge, 
  as 
  will 
  be 
  shown 
  more 
  fully 
  in 
  subse- 
  

   quent 
  pages. 
  

  

  Fig. 
  4 
  Diagram 
  of 
  a 
  portion 
  of 
  a 
  dissected 
  coastal 
  plain, 
  showing 
  old-land 
  on 
  the 
  left, 
  and 
  two 
  

   euestas 
  with 
  their 
  accompanying 
  inner 
  lowlands. 
  Three 
  consequent 
  streams 
  have 
  breached 
  the 
  

   cuestas, 
  and 
  subsequent 
  streams 
  from 
  the 
  lowlands 
  join 
  them. 
  An 
  obsequent 
  stream 
  is 
  shown 
  in 
  

   the 
  center 
  of 
  the 
  outer 
  cuesta. 
  

  

  If 
  we 
  assume 
  that 
  during 
  the 
  greater 
  part 
  of 
  the 
  Mesozoic 
  era, 
  

   the 
  land 
  in 
  this 
  region 
  remained 
  in 
  a 
  constant 
  relation 
  tO' 
  the 
  sea- 
  

   level, 
  it 
  becomes 
  apparent 
  that 
  the 
  southward 
  retreating 
  infaces 
  of 
  

   the 
  cuestas 
  formed 
  by 
  the 
  resistant 
  members 
  of 
  the 
  Paleozoic 
  rocks, 
  

   became 
  lower 
  and 
  lower, 
  as 
  the 
  southward 
  inclination 
  of 
  the 
  strata 
  

   carried 
  the 
  resistant 
  beds 
  nearer 
  and 
  nearer 
  to 
  sealevel. 
  Eventually 
  

   the 
  escarpment 
  character 
  of 
  the 
  infaces 
  must 
  have 
  become 
  obsolete, 
  

   from 
  the 
  disappearance, 
  beneath 
  the 
  erosion 
  level, 
  of 
  the 
  weaker 
  

   lower 
  strata, 
  which 
  permitted 
  the 
  undermining 
  of 
  the 
  capping 
  beds. 
  

   When 
  this 
  occurred, 
  the 
  capping 
  strata 
  alone 
  contiruued 
  ex- 
  

   posed 
  to 
  the 
  action 
  of 
  the 
  atmosphere, 
  and, 
  from 
  a 
  cliff 
  char- 
  

   acter, 
  their 
  exposed 
  ends 
  were 
  planed 
  ofif 
  to 
  a 
  wedge 
  shape, 
  thin- 
  

  

  'W. 
  M. 
  Davis 
  

  

  