﻿102 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  small 
  overthrusts 
  in 
  the 
  Canajoharie 
  shale 
  occur 
  at 
  the 
  dam 
  at 
  

   Fort 
  Edward. 
  Here 
  the 
  shale 
  is 
  already 
  somewhat 
  contorted 
  and 
  

   folds 
  that 
  are 
  inverted 
  to 
  the 
  northwest 
  are 
  exposed. 
  The 
  entire 
  

   mass 
  of 
  rock 
  is, 
  however, 
  cut 
  by 
  a 
  great 
  number 
  of 
  slip 
  or 
  over- 
  

   thrust 
  faults, 
  dipping 
  southeast 
  at 
  12° 
  to 
  14 
  . 
  The 
  throw 
  is 
  always 
  

   very 
  small 
  and 
  the 
  thicker 
  and 
  harder 
  beds 
  in 
  the 
  shale 
  are 
  seen 
  

   to 
  be 
  broken 
  by 
  the 
  slip 
  planes, 
  the 
  upper 
  part 
  being 
  thrust 
  for- 
  

   ward 
  a 
  little 
  over 
  the 
  lower, 
  the 
  whole 
  suggesting 
  surface 
  thrusts. 
  

   These 
  small 
  slips 
  and 
  folds 
  in 
  the 
  eastern 
  margin 
  of 
  the 
  flat 
  shales 
  

   of 
  the 
  western 
  basin 
  were 
  produced 
  either 
  below 
  the 
  overriding 
  

   eastern 
  rock 
  masses 
  or 
  in 
  front 
  of 
  them. 
  The 
  step 
  faults 
  prevail 
  

   therefore 
  in 
  the 
  western 
  part 
  of 
  the 
  belt 
  and 
  the 
  slip 
  faults 
  in 
  the 
  

   eastern. 
  

  

  At 
  Hudson 
  Falls, 
  a 
  few 
  miles 
  north 
  of 
  the 
  Schuylerville 
  quad- 
  

   rangle, 
  the 
  Canajoharie 
  shale, 
  in 
  being 
  pushed 
  northwestward 
  be- 
  

   fore 
  the 
  eastern 
  rock 
  masses, 
  appears 
  to 
  have 
  encountered 
  some 
  

   resistant 
  body 
  which 
  twisted 
  the 
  shales; 
  they 
  are 
  here 
  shattered 
  

   and 
  filled 
  with 
  a 
  great 
  profusion 
  of 
  calcite 
  veins. 
  It 
  seems 
  as 
  

   if 
  the 
  spur 
  of 
  limestones 
  and 
  dolomites 
  that 
  protrudes 
  through 
  the 
  

   shales 
  a 
  mile 
  farther 
  west, 
  at 
  Glens 
  Falls, 
  had 
  been 
  this 
  resistant 
  

   boss. 
  

  

  Folded 
  area. 
  The 
  structure 
  of 
  the 
  folded 
  area 
  is 
  of 
  the 
  most 
  

   complex 
  character 
  imaginable. 
  It 
  will 
  be 
  discussed 
  in 
  two 
  parts, 
  

   (1) 
  the 
  structure 
  of 
  the 
  Ordovicic 
  shale 
  in 
  the 
  Hudson 
  River 
  

   plain, 
  (2) 
  the 
  structure 
  of 
  the 
  Georgian 
  rocks 
  and 
  associated 
  Or- 
  

   dovicic 
  formations 
  in 
  the 
  eastern 
  (Greenwich) 
  hill 
  region. 
  

  

  The 
  shale 
  belt 
  of 
  the 
  Hudson 
  River 
  plain 
  in 
  the 
  folded 
  area 
  

   consists 
  principally 
  of 
  the 
  Normanskill 
  shale 
  in 
  the 
  middle 
  and 
  

   the 
  Snake 
  Hill 
  shale 
  on 
  both 
  sides. 
  This 
  entire 
  mass 
  is 
  uniformly 
  

   thrown 
  into 
  a 
  mass 
  of 
  closely 
  packed, 
  small 
  closed 
  folds 
  that 
  are 
  

   asymmetric 
  and 
  uniformly 
  overturned 
  or 
  inverted 
  to 
  the 
  west, 
  

   so 
  that 
  on 
  the 
  surface 
  and 
  in 
  sections 
  where 
  the 
  tops 
  of 
  the 
  

   anticlines 
  are 
  eroded 
  away, 
  the 
  entire 
  mass 
  has 
  an 
  isoclinal 
  struc- 
  

   ture, 
  all 
  beds 
  dipping 
  to 
  the 
  east 
  with 
  varying 
  angles, 
  averaging 
  

   about 
  70 
  . 
  This 
  is 
  especially 
  true 
  where 
  only 
  shales 
  are 
  involved. 
  

   Where, 
  however, 
  more 
  resistant 
  beds, 
  especially 
  the 
  grit 
  beds, 
  are 
  

   present, 
  these 
  appear 
  to 
  be 
  folded 
  into 
  less 
  compact 
  or 
  closed 
  folds, 
  

   and 
  they 
  are 
  liable 
  to 
  form 
  broad 
  open 
  folds 
  in 
  one 
  place 
  and 
  

   recumbent 
  ones 
  in 
  places 
  near 
  by, 
  as 
  on 
  Snake 
  hill. 
  In 
  the 
  Rocky 
  

   tucks 
  each 
  leg 
  of 
  the 
  inverted 
  anticline 
  forms, 
  as 
  a 
  rule, 
  a 
  ridge 
  

   by 
  itself, 
  the 
  roof 
  or 
  top 
  of 
  the 
  anticline 
  being 
  broken 
  out. 
  These 
  

  

  