﻿THE 
  GEOLOGICAL 
  HISTORY 
  OF 
  NEW 
  YORK 
  STATE 
  73 
  

  

  valley. 
  To 
  a 
  considerable 
  degree 
  the 
  topography 
  of 
  the 
  valley 
  is 
  

   affected 
  by 
  the 
  faults, 
  especially 
  where 
  the 
  harder 
  Precambric 
  or 
  

   Cambric 
  rocks 
  form 
  the 
  scarp 
  or 
  upthrow 
  sides 
  of 
  the 
  faults. 
  This 
  

   is 
  particularly 
  true 
  at 
  Little 
  Falls 
  and 
  the 
  " 
  Noses 
  " 
  (near 
  Yosts) 
  

   where, 
  in 
  each 
  case,, 
  the 
  Mohawk 
  river 
  has 
  cut 
  a 
  gorge 
  across 
  a 
  

   prominent 
  fault 
  scarp 
  and 
  even 
  down 
  to 
  the 
  underlying 
  Precambric 
  

   rock 
  which 
  has 
  been 
  brought 
  relatively 
  nearer 
  the 
  surface 
  by 
  the 
  

   tilting 
  of 
  the 
  earth 
  blocks 
  (see 
  figure 
  7). 
  On 
  the 
  geologic 
  map 
  of 
  

   the 
  State 
  (figure 
  1) 
  two 
  tongues 
  of 
  Paleozoic 
  rock 
  are 
  seen 
  to 
  

   extend 
  northward 
  well 
  into 
  the 
  Precambric 
  rock 
  area, 
  and 
  these 
  are 
  

   to 
  be 
  explained 
  by 
  the 
  fact 
  that, 
  due 
  to 
  faulting 
  along 
  the 
  west 
  

   sides, 
  the 
  Paleozoic 
  strata, 
  for 
  fifteen 
  or 
  twenty 
  miles, 
  have 
  dropped 
  

   down 
  (relatively) 
  fully 
  1500 
  feet 
  with 
  respect 
  to 
  the 
  Precambric 
  

   rock. 
  The 
  much 
  more 
  resistant 
  Precambric 
  rock 
  has 
  stood 
  out 
  

   against 
  erosion 
  and 
  in 
  each 
  case 
  rises 
  with 
  steep 
  front 
  from 
  1000 
  

   to 
  1500 
  feet 
  above 
  the 
  Paleozoic 
  rock 
  surface 
  (see 
  figure 
  26). 
  The 
  

   small 
  remnant 
  of 
  Paleozoic 
  strata 
  already 
  referred 
  to 
  at 
  Wells 
  in 
  

   Hamilton 
  county 
  was 
  dropped 
  down 
  fully 
  2000 
  feet 
  by 
  faulting 
  

   against 
  the 
  Precambric 
  rock 
  just 
  west, 
  and 
  thus 
  this 
  remarkable 
  

   Paleozoic 
  outlier 
  has 
  been 
  preserved 
  from 
  complete 
  removal 
  by 
  

   erosion. 
  

  

  What 
  is 
  the 
  age 
  of 
  the 
  faulting 
  or, 
  in 
  other 
  words, 
  when 
  were 
  

   these 
  fractures 
  developed? 
  That 
  some 
  faulting, 
  at 
  least, 
  occurred 
  

   during 
  Precambric 
  time 
  has 
  been 
  well 
  established 
  but, 
  so 
  far 
  as 
  

   known, 
  those 
  faults 
  are 
  of 
  very 
  minor 
  importance, 
  certainly 
  having 
  

   no 
  appreciable 
  influence 
  upon 
  the 
  existing 
  topography. 
  

  

  During 
  the 
  Paleozoic 
  era, 
  however, 
  there 
  is 
  good 
  reason 
  to 
  think 
  

   that 
  considerable 
  faulting 
  took 
  place. 
  At 
  just 
  what 
  time 
  during 
  the 
  

   era 
  the 
  faulting 
  occurred 
  is 
  not 
  now 
  altogether 
  certain, 
  but 
  it 
  is 
  

   certain 
  that 
  it 
  was 
  sometime 
  after 
  the 
  deposition 
  of 
  the 
  Ordovicic 
  

   sediments 
  because 
  at 
  many 
  places 
  those 
  rocks 
  are 
  involved 
  in 
  the 
  

   faulting. 
  Cushing 
  has 
  suggested 
  that 
  the 
  faulting 
  may 
  have 
  been 
  

   initiated 
  at 
  the 
  time 
  of 
  the 
  Taconic 
  revolution 
  when 
  the 
  rocks 
  of 
  

   the 
  region 
  immediately 
  eastward 
  were 
  so 
  greatly 
  disturbed, 
  but 
  he 
  

   says, 
  " 
  the 
  great 
  earth 
  disturbances 
  (Appalachian 
  revolution) 
  which 
  

   prevailed 
  in 
  the 
  Appalachian 
  zone 
  toward 
  the 
  close 
  of 
  the 
  Paleozoic 
  

   would 
  seem 
  more 
  likely 
  to 
  have 
  brought 
  about 
  the 
  major 
  faulting 
  

   of 
  the 
  reigon." 
  x 
  At 
  this 
  latter 
  time 
  the 
  rocks 
  of 
  northern 
  New 
  

   York 
  were 
  not 
  folded 
  but, 
  as 
  we 
  have 
  learned, 
  the 
  whole 
  State 
  was 
  

   notably 
  elevated, 
  and 
  during 
  this 
  disturbance 
  conditions 
  were 
  cer- 
  

  

  1 
  N. 
  Y. 
  State 
  Mus. 
  Bui. 
  95, 
  p. 
  405. 
  

  

  