﻿14 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  of 
  thrust 
  faulting- 
  are 
  here 
  absent. 
  In 
  many 
  places 
  the 
  close 
  

   proximity 
  of 
  folded 
  gneiss 
  and 
  overlying 
  quartzite 
  show 
  the 
  great 
  

   discordance 
  in 
  the 
  dip 
  of 
  the 
  two 
  and 
  less 
  distinctly, 
  though 
  plainly, 
  

   in 
  that 
  of 
  the 
  strike. 
  In 
  places 
  the 
  two 
  are 
  so 
  near 
  that 
  for 
  all 
  

   practical 
  purposes 
  we 
  are 
  dealing 
  with 
  the 
  actual 
  contacts. 
  The 
  

   relationship 
  presents 
  the 
  aspect 
  of 
  an 
  overlapping 
  sea. 
  Leaving 
  the 
  

   gneisses 
  at 
  the 
  south, 
  one 
  successively 
  passes 
  over 
  the 
  quartzite 
  

   and 
  overlying 
  limestones 
  northward 
  until 
  lost 
  in 
  the 
  close 
  folding 
  

   there 
  prevailing. 
  Erosion 
  has 
  greatly 
  trenched 
  the 
  comparatively 
  

   soluble 
  limestones 
  of 
  the 
  Fishkill 
  belt 
  and 
  has 
  planed 
  these 
  strata 
  

   down 
  nearly 
  to 
  a 
  common 
  level 
  across 
  the 
  faults 
  and 
  folds. 
  The 
  

   confusion 
  resulting 
  does 
  not 
  conceal 
  the 
  substantial 
  thickness 
  of 
  the 
  

   limestone 
  strata 
  and 
  the 
  great 
  thickness 
  of 
  the 
  slates 
  and 
  schists 
  

   of 
  the 
  Hudson 
  valley 
  to 
  the 
  northward 
  only 
  strengthens 
  the 
  con- 
  

   viction 
  that 
  they, 
  with 
  the 
  limestones, 
  once 
  covered 
  the 
  tops 
  and 
  

   filled 
  the 
  valleys 
  of 
  the 
  Highlands 
  over 
  which 
  they 
  were 
  carried 
  

   by 
  an 
  overlapping 
  sea 
  that 
  progressively 
  advanced 
  over 
  a 
  subsiding 
  

   Precambric 
  land 
  mass. 
  

  

  It 
  is 
  proposed 
  in 
  the 
  later 
  report 
  to 
  discuss 
  in 
  this 
  connection 
  

   the 
  occurrence 
  of 
  scattered 
  masses 
  of 
  the 
  younger 
  rocks 
  met 
  with 
  

   in 
  the 
  Highlands 
  and 
  to 
  suggest 
  explanations 
  for 
  these 
  occurrences. 
  

   It 
  is 
  purposed, 
  also, 
  to 
  discuss 
  the 
  significance 
  of 
  the 
  great 
  block 
  

   fault 
  south 
  of 
  the 
  Highlands, 
  which 
  has 
  dropped 
  the 
  younger 
  rocks 
  

   of 
  southeastern 
  New 
  York 
  and 
  the 
  shattering 
  which 
  the 
  Highlands 
  

   mass 
  received 
  from 
  the 
  forces 
  producing 
  this- 
  and 
  other 
  faults. 
  

   Some 
  treatment 
  will 
  necessarily 
  be 
  given 
  to 
  the 
  proposition 
  that 
  a 
  

   combination 
  of 
  forces, 
  acting 
  as 
  a 
  gigantic 
  couple, 
  the 
  resultant 
  of 
  

   the 
  westward 
  tangential" 
  pressures 
  operated 
  with 
  the 
  Adirondack 
  

   Precambric 
  buttress 
  to 
  induce 
  strike 
  and 
  transverse 
  faulting 
  of 
  an 
  

   exceptionally 
  violent 
  sort 
  in 
  the 
  powerfully 
  elastic 
  rocks 
  of 
  the 
  

   Hudson 
  valley. 
  

  

  Highlands 
  of 
  the 
  quadrangle. 
  The 
  general 
  petrography 
  and 
  

   stratigraphy 
  point 
  to 
  a 
  Precambric 
  sedimentary 
  series 
  v/ith 
  a 
  Pre- 
  

   cambric 
  intrusive 
  sill, 
  or 
  bathylith', 
  and 
  some 
  apparently 
  later 
  in- 
  

   trusions. 
  The 
  discovery 
  of 
  an 
  altered 
  limestone 
  interbedded 
  with 
  

   the 
  gneisses, 
  the 
  heterogeneous 
  character 
  of 
  the 
  gneisses 
  them- 
  

   selves 
  and 
  the 
  occurrence 
  of 
  repetitions 
  within 
  them 
  of 
  certain 
  

   rock 
  types, 
  as 
  well 
  as, 
  apparently, 
  some 
  plainer 
  evidence 
  of 
  bed- 
  

   ding, 
  are 
  taken 
  as 
  the 
  principal 
  evidences 
  of 
  a 
  sedimentary 
  origin. 
  

   Microscopic 
  evidence 
  will 
  be 
  presented. 
  No 
  graphitic 
  strata 
  have 
  

   been 
  noted. 
  The 
  structural 
  features 
  belong 
  both 
  to 
  Precambric 
  and 
  

   later 
  time. 
  Later 
  deformations 
  have 
  been 
  superimposed 
  on 
  earlier 
  

  

  