﻿54 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  Still 
  more 
  recent 
  work 
  on 
  some 
  of 
  the 
  faults 
  which 
  reach 
  the 
  

   Saratoga 
  quadrangle 
  has 
  been 
  done 
  by 
  Prosser, 
  Cumings 
  and 
  Fisher 
  

   in 
  their 
  mapping 
  of 
  the 
  Hoflmans 
  Ferry 
  fault 
  across 
  the 
  Amster- 
  

   dam 
  quadrangle, 
  near 
  the 
  north 
  edge 
  of 
  which 
  it 
  gives 
  rise 
  to 
  two 
  

   branches; 
  and 
  by 
  Miller 
  in 
  his 
  mapping 
  of 
  these 
  and 
  other 
  faults 
  

   of 
  the 
  Broadalbin 
  quadrangle. 
  1 
  Of 
  these 
  only 
  the 
  Hoflmans 
  Ferry 
  

   fault 
  and 
  branches 
  pass 
  over 
  on 
  the 
  Saratoga 
  quadrangle, 
  while 
  

   other 
  and 
  more 
  easterly 
  faults 
  come 
  in. 
  

  

  All 
  the 
  larger 
  of 
  these 
  Mohawk 
  faults 
  have 
  a 
  trend 
  somewhat 
  

   to 
  the 
  east 
  of 
  north, 
  and 
  a 
  rude 
  parallelism 
  with 
  one 
  another. 
  To 
  

   the 
  south 
  they 
  all 
  run 
  into 
  the 
  great 
  thickness 
  of 
  upper 
  Ordovicic 
  

   shales, 
  and 
  as 
  soon 
  as 
  these 
  come 
  to 
  form 
  the 
  surface 
  rocks 
  on 
  both 
  

   sides 
  of 
  the 
  fault, 
  it 
  is 
  exceedingly 
  difficult 
  to 
  trace 
  the 
  dislocation 
  

   farther. 
  We 
  do 
  not 
  as 
  yet 
  know 
  whether 
  they 
  die 
  out 
  in 
  the 
  shales 
  

   or 
  not. 
  To 
  the 
  north 
  the 
  faults 
  run 
  into 
  the 
  Precambric 
  rocks; 
  

   and 
  so 
  soon 
  as 
  they 
  have 
  these 
  on 
  both 
  sides 
  of 
  the 
  fault, 
  a 
  similar 
  

   difficulty 
  arises 
  in 
  the 
  effort 
  to 
  trace 
  them 
  farther. 
  But 
  they 
  seem 
  

   to 
  run 
  entirely 
  across 
  the 
  Adirondack 
  region 
  from 
  south 
  to 
  north 
  

   and 
  diminish 
  in 
  frequency 
  toward 
  the 
  west. 
  Hence 
  it 
  results 
  that 
  

   they 
  abound 
  in 
  the 
  southeast 
  border 
  of 
  the 
  region 
  and 
  are 
  practi- 
  

   cally 
  absent 
  on 
  the 
  northwest. 
  With 
  their 
  parallelism 
  they 
  divide 
  

   the 
  region 
  into 
  a 
  great 
  series 
  of 
  rock 
  slices 
  or 
  segments 
  which 
  have 
  

   shifted 
  up 
  and 
  down 
  past 
  one 
  another 
  and 
  broken 
  the 
  continuity 
  

   of 
  the 
  rock 
  formations. 
  

  

  The 
  fault 
  planes 
  are 
  seldom 
  visible 
  but 
  such 
  evidence 
  as 
  we 
  have 
  

   indicates 
  that 
  they 
  are 
  nearly 
  vertical 
  breaks 
  and 
  are 
  all 
  of 
  the 
  type 
  

   known 
  as 
  normal 
  faults. 
  In 
  the 
  great 
  majority 
  of 
  them 
  the 
  east 
  side 
  

   has 
  dropped 
  in 
  level 
  relatively 
  to 
  the 
  west 
  side, 
  but 
  in 
  a 
  few 
  of 
  

   them 
  the 
  reverse 
  is 
  true. 
  

  

  In 
  addition 
  to 
  the 
  relative 
  displacements 
  of 
  the 
  adjacent 
  slices 
  

   along 
  the 
  fault 
  planes, 
  the 
  upper 
  surfaces 
  of 
  the 
  slices 
  have 
  usually 
  

   received 
  a 
  tilt 
  toward 
  the 
  west, 
  each 
  slice 
  thus 
  constituting 
  the 
  up- 
  

   throw 
  side 
  of 
  a 
  fault 
  along 
  its 
  east 
  edge, 
  and 
  the 
  downthrow 
  side 
  

   of 
  the 
  next 
  fault 
  along 
  its 
  west 
  edge, 
  as 
  illustrated 
  in 
  figure 
  4. 
  

  

  The 
  faults. 
  Two 
  of 
  the 
  great 
  faults 
  of 
  the 
  Mohawk 
  region, 
  the 
  

   Hoffmans 
  Ferry 
  (much 
  better 
  abbreviated 
  to 
  Hoffmans) 
  and 
  the 
  

   McGregor 
  fault, 
  the 
  latter 
  here 
  named 
  for 
  the 
  first 
  time, 
  cross 
  the 
  

   Saratoga 
  quadrangle. 
  The 
  remaining 
  faults 
  mapped 
  are 
  branches 
  

   of 
  these 
  two 
  great 
  breaks. 
  

  

  1 
  N. 
  Y. 
  State 
  Mus. 
  Bui. 
  34 
  and 
  map; 
  Bui. 
  153 
  and 
  map. 
  

  

  