﻿110 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  Cambrian 
  beds 
  are 
  all 
  in 
  minor 
  folds, 
  as 
  are 
  certainly 
  the 
  several 
  isolated 
  

   Ordovician 
  areas 
  and 
  the 
  large 
  central 
  ramifying 
  ones. 
  And 
  there 
  is 
  no 
  

   evidence 
  of 
  such 
  a 
  great 
  overthrust 
  as 
  at 
  Burlington 
  and 
  Saint 
  Albans. 
  But 
  

   Mr 
  Walcott 
  does 
  find 
  evidence 
  of 
  an 
  overthrust 
  on 
  Bald 
  mountain, 
  in 
  the 
  

   town 
  of 
  Greenwich, 
  in 
  Washington 
  county, 
  New 
  York, 
  west 
  of 
  the 
  slate 
  belt. 
  

   The 
  exposures 
  described 
  near 
  North 
  Granville 
  (page 
  292) 
  also 
  indicate 
  

   reverse 
  faulting. 
  Yet 
  the 
  course 
  of 
  the 
  Cambro-Ordovician 
  boundary 
  along 
  

   the 
  western 
  edge 
  of 
  the 
  slate 
  belt, 
  particularly 
  northeast 
  and 
  southwest 
  of 
  

   North 
  Granville, 
  New 
  York, 
  and 
  in 
  Benson 
  and 
  Hubbardton, 
  Vermont, 
  and 
  

   again 
  in 
  the 
  townships 
  of 
  Hartford, 
  Argyle, 
  and 
  Hebron, 
  New 
  York, 
  is 
  

   hardly 
  consistent 
  with 
  the 
  existence 
  there 
  of 
  a 
  great 
  longitudinal 
  overthrust, 
  

   nor 
  do 
  the 
  vertical 
  relations 
  of 
  the 
  Ordovician 
  and 
  Cambrian 
  outcrops 
  favor 
  

   such 
  a 
  construction. 
  If 
  such 
  a 
  thrust 
  plane 
  separates 
  the 
  two 
  formations, 
  it 
  

   must 
  be 
  a 
  folded 
  thrust 
  plane, 
  which 
  is 
  not 
  an 
  ordinary 
  probability. 
  

  

  It 
  would 
  appear, 
  therefore, 
  that 
  the 
  great 
  mid-Silurian 
  orogenic 
  movement 
  

   which, 
  in 
  northern 
  Vermont, 
  operating 
  upon 
  rigid 
  beds, 
  found 
  relief 
  in 
  a 
  

   great 
  overthrust, 
  at 
  the 
  south, 
  near 
  the 
  slate 
  belt, 
  operating 
  upon 
  beds 
  which 
  

   were 
  more 
  plastic, 
  compressed 
  them 
  into 
  minute 
  folds. 
  In 
  either 
  case 
  the 
  

   compression 
  at 
  the 
  south 
  found 
  relief 
  chiefly 
  in 
  folding, 
  and 
  only 
  here 
  and 
  

   there, 
  as 
  about 
  North 
  Granville 
  and 
  at 
  Bald 
  mountain, 
  in 
  faulting. 
  But 
  evi- 
  

   dences 
  of 
  faulting 
  may 
  be 
  found 
  west 
  of 
  the 
  area 
  here 
  mapped. 
  

  

  In 
  1901 
  (page 
  555ff.) 
  the 
  writer 
  explained 
  the 
  inverted 
  order 
  of 
  

   the 
  formations 
  observed 
  by 
  him 
  in 
  the 
  neighborhood 
  of 
  Albany 
  

   by 
  an 
  overturned 
  fold 
  which 
  changed 
  into 
  an 
  overthrust 
  fault,, 
  

   whereby 
  the 
  Georgian 
  became 
  overthrust 
  upon 
  the 
  underturned 
  

   wing. 
  This 
  view 
  was 
  also 
  reached 
  by 
  Dale 
  in 
  the 
  Geology 
  of 
  the 
  

   Hudson 
  Valley 
  between 
  the 
  Hoosic 
  and 
  the 
  Kinderhook 
  (1904, 
  

   page 
  38). 
  He 
  states: 
  "That 
  the 
  relations 
  on 
  the 
  west 
  side 
  of 
  

   the 
  Cambrian 
  belt 
  are 
  not 
  only 
  those 
  of 
  unconformable 
  deposi- 
  

   tion 
  but 
  of 
  more 
  or 
  less 
  continuous 
  overthrust 
  is 
  rendered 
  some- 
  

   what 
  probable 
  from 
  the 
  situation 
  of 
  the 
  overthrust 
  near 
  Schodack 
  

   Landing 
  and 
  of 
  that 
  at 
  Bald 
  mountain 
  in 
  Greenwich, 
  47 
  miles 
  

   north-northeast 
  of 
  the 
  former, 
  as 
  well 
  as 
  from 
  the 
  general 
  direc- 
  

   tion 
  of 
  the 
  Cambro-Hudson 
  boundary 
  between 
  them. 
  . 
  . 
  . 
  For 
  

   these 
  reasons 
  it 
  is 
  assumed 
  that 
  in 
  consequence 
  of 
  a 
  westwardly 
  

   overturned 
  fold, 
  which 
  is 
  frequently 
  ruptured, 
  the 
  Lower 
  Cam- 
  

   brian 
  here 
  usually 
  overlies 
  the 
  Hudson, 
  that 
  is, 
  the 
  Trenton 
  or 
  

   middle 
  part 
  of 
  the 
  Ordovician." 
  

  

  The 
  subsequent 
  work 
  of 
  the 
  writer 
  seems 
  to 
  indicate 
  that 
  this 
  

   view 
  as 
  to 
  the 
  origin 
  of 
  the 
  overthrust 
  of 
  the 
  western 
  margin 
  in 
  

   which 
  he 
  and 
  Dale 
  agree, 
  is 
  the 
  one 
  nearest 
  the 
  truth. 
  We 
  see 
  

   possible 
  evidence 
  of 
  this 
  hypothesis 
  in 
  the 
  belt 
  of 
  Bald 
  Mountain 
  

   limestone 
  of 
  Beekmantown 
  age, 
  outcropping 
  below 
  the 
  Georgian 
  

  

  