﻿FIFTH 
  REPORT 
  OF 
  THE 
  DIRECTOR 
  I908 
  I3 
  

  

  extensive 
  fault 
  and 
  thrust 
  movements 
  we 
  may 
  infer 
  the 
  existence 
  of 
  

   similar 
  ones 
  to 
  the 
  south 
  and 
  east 
  which 
  may 
  serve 
  to 
  explain 
  

   some 
  of 
  the 
  difficult 
  phenomena 
  there 
  exhibited, 
  in 
  the 
  presence, 
  

   or 
  absence, 
  or 
  metamorphism 
  of 
  the 
  younger 
  rocks 
  and 
  in 
  the 
  

   intrarelationships 
  among 
  the 
  basal 
  gneisses. 
  

  

  Thrust 
  movements 
  of 
  considerable 
  magnitude, 
  measured 
  by 
  

   hundreds 
  or 
  a 
  few 
  thousand 
  feet, 
  are 
  occasional 
  and 
  numerous 
  

   smaller 
  adjustment 
  faults 
  are 
  frequent. 
  No 
  evidence 
  has 
  been 
  

   secured 
  of 
  displacements 
  on 
  the 
  west 
  of 
  the 
  Highlands 
  axis 
  which 
  

   are 
  supposed 
  to 
  have 
  carried 
  the 
  strata 
  for 
  distances 
  of 
  miles 
  ; 
  and 
  

   were 
  the 
  strata 
  that 
  once 
  overlay 
  this 
  region 
  to 
  be 
  restored 
  it 
  is 
  

   probable 
  that 
  the 
  extent 
  of 
  overturning 
  and 
  overthrusting 
  could 
  be 
  

   measured 
  by 
  a 
  few 
  thousand 
  feet. 
  

  

  The 
  present 
  altitude 
  of 
  the 
  Highlands 
  with 
  respect 
  to 
  the 
  

   neighboring 
  Paleozoics 
  serves 
  in 
  general 
  as 
  no 
  indication 
  of 
  the 
  

   former 
  early 
  relations 
  between 
  these 
  great 
  rock 
  divisions. 
  Folding, 
  

   faulting 
  and 
  erosion, 
  each 
  or 
  all, 
  perhaps, 
  repeated, 
  have 
  combined 
  

   to 
  efface 
  the 
  original 
  early 
  relationship. 
  We 
  seize 
  upon 
  what 
  

   time 
  has 
  left 
  with 
  the 
  hope 
  of 
  untangling 
  the 
  maze 
  that 
  now 
  con- 
  

   fronts 
  us. 
  

  

  The 
  sky-line 
  of 
  the 
  summits 
  of 
  the 
  Highlands 
  knobs 
  and 
  ridges 
  

   even 
  with 
  that 
  of 
  more 
  distant 
  hills 
  among* 
  the 
  younger 
  rocks 
  

   presents 
  the 
  aspect 
  of 
  a 
  former 
  base 
  level 
  that 
  is 
  unmistakable. 
  

   What 
  masses 
  of 
  overlying 
  strata 
  have 
  been 
  removed 
  from 
  these 
  

   crystalline 
  Highlands 
  rocks 
  we 
  can 
  only 
  guess 
  from 
  the 
  thickness 
  

   of 
  those 
  to 
  the 
  northward, 
  the 
  character 
  of 
  the 
  folding 
  there, 
  and 
  

   the 
  length 
  of 
  time 
  the 
  region 
  has 
  suffered 
  denudation. 
  Lofty 
  

   mountain 
  ridges 
  were 
  reduced 
  from 
  alpine 
  bights 
  to 
  a 
  peneplain. 
  

   From 
  their 
  stumps 
  we 
  are 
  obliged 
  to 
  construct 
  our 
  imperfect 
  history 
  

   of 
  the 
  region. 
  

  

  Perhaps 
  in 
  no 
  other 
  place 
  in 
  eastern 
  North 
  America 
  is 
  the 
  con- 
  

   tact 
  of 
  the 
  lowest 
  Paleozoics 
  on 
  the 
  underlying 
  Precambric 
  better 
  

   preserved 
  than 
  on 
  the 
  flanks 
  of 
  the 
  Highlands 
  of 
  southeastern 
  New 
  

   York 
  and 
  nowhere 
  is 
  it 
  better 
  shown 
  than 
  on 
  the 
  northern 
  slope 
  

   of 
  the 
  Fishkill 
  mountains. 
  

  

  Here 
  for 
  considerable 
  distances 
  the 
  basal 
  Cambric 
  quartzite 
  rests 
  

   unconformably 
  upon 
  the 
  folded 
  basal 
  gneisses. 
  The 
  forces 
  of 
  

   erosion 
  that 
  have 
  removed 
  the 
  quartzite 
  and 
  the 
  overlying 
  lime- 
  

   stones, 
  which 
  once 
  filled 
  the 
  northern 
  valleys 
  of 
  these 
  mountains, 
  

   have 
  cut 
  deeply 
  enough 
  to 
  expose 
  a 
  faulted 
  block 
  of 
  the 
  basal 
  

   Paleozoics 
  where 
  the 
  relationships 
  have 
  been 
  well 
  preserved. 
  The 
  

   usual 
  abnormal 
  relationships 
  present 
  along 
  this 
  border 
  as 
  a 
  result 
  

  

  