﻿210 
  F. 
  Leverett- 
  — 
  Pleistocene 
  Fluvial 
  Planes 
  of 
  

  

  Taking 
  into 
  consideration 
  all 
  the 
  known 
  facts, 
  it 
  certainly 
  

   seems 
  premature 
  to 
  urge, 
  without 
  distinct 
  qualification, 
  the 
  

   acceptance 
  of 
  a 
  hypothesis 
  of 
  northward 
  drainage 
  for 
  any 
  of 
  

   these 
  streams 
  during 
  the 
  interglacial 
  epoch, 
  and 
  much 
  more 
  so 
  

   to 
  impose 
  a 
  name 
  for 
  the 
  unproven 
  river. 
  

  

  Moraine-headed 
  terraces. 
  — 
  President 
  Chamberlin's 
  descrip- 
  

   tion 
  of 
  the 
  moraine-headed 
  terraces 
  and 
  general 
  remarks 
  upon 
  

   the 
  history 
  of 
  the 
  several 
  fluvial 
  planes 
  embody 
  so 
  well 
  the 
  

   essential 
  facts 
  that 
  further 
  remarks 
  are 
  unnecessary. 
  From 
  

   his 
  paper 
  the 
  following 
  extracts 
  are 
  taken 
  verbatim.* 
  

  

  " 
  The 
  third 
  group 
  of 
  terraces 
  are 
  sharply 
  distinguishable 
  

   from 
  those 
  which 
  have 
  just 
  been 
  considered; 
  first, 
  in 
  the 
  fact 
  

   that, 
  instead 
  of 
  being 
  rock 
  platforms 
  covered 
  by 
  fluvial 
  mate- 
  

   rial, 
  they 
  are 
  made 
  up 
  bodily 
  of 
  coarse 
  alluvium, 
  mainly 
  gravel. 
  

   They 
  have 
  their 
  chief 
  development 
  in 
  the 
  rivers 
  entering 
  the 
  

   Ohio 
  from 
  the 
  north, 
  and 
  when 
  traced 
  up 
  they 
  are 
  found 
  to 
  

   head 
  on 
  one 
  of 
  the 
  moraines 
  of 
  the 
  later 
  glacial 
  epoch, 
  or 
  at 
  

   least 
  of 
  a 
  later 
  glacial 
  epoch 
  following 
  at 
  a 
  considerable 
  inter- 
  

   val 
  an 
  earlier 
  one. 
  The 
  uppermost 
  of 
  these 
  terraces 
  has 
  for 
  its 
  

   surface 
  plane 
  the 
  ancient 
  flood 
  deposits 
  of 
  the 
  glacier-fed 
  streams. 
  

   The 
  lower 
  terraces 
  have 
  been 
  cut 
  out 
  of 
  it 
  by 
  subsequent 
  

   erosion. 
  Near 
  the 
  moraine 
  this 
  upper 
  glacial 
  flood 
  surface 
  

   may 
  be 
  traced 
  continuously, 
  rising 
  somewhat 
  rapidly 
  as 
  the 
  

   moraine 
  is 
  approached, 
  and 
  passing 
  gradually 
  into 
  a 
  series 
  of 
  

   undulations 
  which 
  merge 
  into 
  the 
  gravelly 
  knobs 
  and 
  basins, 
  

   and 
  thence 
  into 
  the 
  unassorted 
  hills 
  of 
  the 
  moraine. 
  This 
  

   relationship 
  was 
  satisfactorily 
  observed 
  by 
  Mr. 
  Gilbert 
  and 
  

   nryself, 
  separately 
  or 
  jointly, 
  on 
  Conewango 
  creek, 
  near 
  Rus- 
  

   sellburg 
  ; 
  on 
  the 
  Little 
  Brokenstraw, 
  near 
  Freehold 
  ; 
  on 
  the 
  

   Big 
  Brokenstraw, 
  near 
  Horn's 
  Siding 
  ; 
  and 
  on 
  Oil 
  creek 
  near 
  

   Hydetown. 
  On 
  Sugar 
  creek, 
  French 
  creek, 
  and 
  Sandy 
  creek 
  

   phenomena 
  of 
  similar 
  significance 
  appeal', 
  but 
  they 
  are 
  less 
  

   clear 
  in 
  their 
  import. 
  On 
  Beaver 
  river 
  and 
  Little 
  Beaver 
  

   creek 
  analogous 
  features 
  are 
  more 
  satisfactorily 
  displayed. 
  

  

  The 
  streams 
  of 
  gravel 
  starting 
  in 
  these 
  morainic 
  heads 
  run 
  

   down 
  through 
  the 
  rock 
  channels 
  cut 
  below 
  the 
  old 
  river 
  bottom 
  

   as 
  above 
  described. 
  The 
  surfaces 
  of 
  these 
  later 
  glacial 
  gravel 
  

   streams 
  are 
  generally 
  much 
  below 
  that 
  of 
  the 
  earlier 
  terrace 
  

   deposits, 
  but 
  as 
  they 
  slope 
  more 
  rapidly 
  there 
  is 
  no 
  constant 
  

   difference. 
  An 
  interval 
  of 
  from 
  100 
  to 
  200 
  feet 
  may 
  be 
  taken 
  

   as 
  representative. 
  The 
  bottom 
  of 
  these 
  later 
  glacial 
  gravels 
  

   extends 
  below 
  the 
  present 
  river-beds, 
  reaching 
  depths 
  varying 
  

   from 
  40 
  feet 
  to 
  250 
  feet 
  or 
  more, 
  showing 
  a 
  considerable 
  depth 
  

   of 
  channel 
  before 
  this 
  late 
  filling. 
  These 
  terraces 
  reach 
  their 
  

   greatest 
  height 
  above 
  the 
  present 
  stream, 
  so 
  far 
  as 
  observed, 
  at 
  

   the 
  junction 
  of 
  the 
  Beaver 
  river 
  with 
  the 
  Ohio. 
  There 
  the 
  

  

  * 
  Bulletin 
  No. 
  58, 
  U. 
  S. 
  Geol. 
  Sur., 
  1890, 
  pp. 
  32-36. 
  

  

  