﻿NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  overdeepening- 
  of 
  the 
  valleys 
  has 
  taken 
  place 
  that 
  leads 
  to 
  exposures 
  

   of 
  deeper 
  beds 
  surrounded 
  by 
  younger 
  beds, 
  a 
  process 
  ascribed 
  by 
  

   some 
  glacialists 
  to 
  glacial 
  erosion. 
  While 
  on 
  account 
  of 
  the 
  con- 
  

  

  FlG. 
  

  

  Diagrammatic 
  section 
  of 
  a 
  " 
  s^r.k 
  " 
  or 
  " 
  cove", 
  the 
  black 
  lirxe 
  indicating 
  the 
  

   subterranean 
  water 
  course 
  

  

  siderable 
  depth 
  of 
  most 
  of 
  these 
  lakes, 
  there 
  is 
  no 
  doubt 
  that 
  their 
  

   bottoms 
  reach 
  down 
  even 
  into 
  Siluric 
  beds 
  when 
  their 
  shores 
  are 
  

   in 
  the 
  Devonic, 
  but 
  the 
  maps 
  do 
  not 
  suggest 
  this 
  fact, 
  except 
  in 
  a 
  

   very 
  few 
  instances. 
  One 
  of 
  these 
  that 
  appears 
  quite 
  convincing 
  

   is 
  the 
  exposure 
  of 
  Middlesex 
  black 
  shale 
  along 
  the 
  west 
  branch 
  

   of 
  Keuka 
  lake^ 
  and 
  in 
  the 
  lower 
  portion 
  of 
  the 
  valley 
  lying 
  in 
  

   the 
  continuation 
  of 
  the 
  lake 
  [see 
  text 
  fig. 
  19]. 
  This 
  long 
  out- 
  

   crop 
  of 
  Middlesex 
  shale 
  is 
  entirely 
  isolated 
  and 
  surrounded 
  by 
  the 
  

   overlying 
  Neodevonic 
  beds 
  "" 
  ( 
  Cashaqua 
  shale, 
  etc.) 
  In 
  this 
  case 
  it 
  

   would 
  seem 
  that 
  the 
  north-south 
  flowing 
  brook, 
  emptying 
  at 
  

   Branchport, 
  and 
  running 
  with 
  the 
  dip 
  of 
  the 
  rocks, 
  found 
  itself 
  in 
  

   the 
  condition 
  described 
  above 
  under 
  corrasion 
  inliers 
  and 
  thus 
  

   might 
  have 
  alone 
  been 
  competent 
  to- 
  produce 
  a 
  part 
  o'f 
  the 
  inlier, 
  

   although 
  its 
  short 
  length 
  and 
  small 
  size 
  and 
  the 
  great 
  length 
  of 
  the 
  

   inlier 
  and 
  depth 
  of 
  lake 
  basin 
  indicating 
  a 
  great 
  amount 
  of 
  erosion, 
  

   are 
  now 
  entirely 
  out 
  of 
  proportion 
  and 
  glacier 
  ice 
  is 
  therefore 
  to 
  

   be 
  appealed 
  to 
  as 
  a 
  factor, 
  especially 
  in 
  regard 
  to 
  the 
  inlier 
  of 
  the 
  

   west 
  branch 
  of 
  the 
  lake. 
  

  

  We 
  have 
  thus 
  far 
  considered 
  the 
  inliers 
  wdiich 
  originate 
  from 
  

   the 
  agency 
  of 
  water, 
  in 
  either 
  depositing 
  or 
  eroding. 
  We 
  now 
  

   j:urn 
  to 
  the 
  more 
  important 
  groups 
  of 
  inliers 
  produced 
  by 
  diastro- 
  

   phism. 
  These 
  are 
  the 
  fold 
  and 
  fault 
  inliers. 
  

  

  3 
  Fold 
  inliers. 
  These 
  are 
  formed 
  a 
  on 
  the 
  suinmits 
  either 
  of 
  a^ 
  

   normal 
  antichnes 
  or 
  a., 
  domes 
  (" 
  uplifts," 
  " 
  parmas 
  ") 
  or 
  b 
  through 
  

   overturned 
  folds 
  ('' 
  Klippen 
  "). 
  

  

  We 
  will 
  first 
  consider 
  those 
  very 
  frequent 
  cases 
  of 
  infiers 
  of 
  

   rocks, 
  appearing 
  on 
  summits 
  of 
  normal 
  folds 
  through 
  erosion. 
  

  

  ^ 
  Luther, 
  D. 
  D. 
  Penn 
  Yan-Hammondsport 
  Quadrangles, 
  N. 
  Y. 
  State 
  Mus. 
  

   Bui. 
  loi. 
  igo6. 
  

  

  