﻿56 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  The 
  Hoffmans 
  fault 
  enters 
  the 
  Saratoga 
  quadrangle 
  on 
  its 
  west 
  

   margin 
  I 
  mile 
  northwest 
  of 
  East 
  Galway 
  and, 
  pursuing 
  a 
  general 
  

   north-northeast 
  course 
  passes 
  on 
  to 
  the 
  Luzerne 
  sheet 
  a 
  mile 
  west 
  

   of 
  Corinth. 
  At 
  Hoffmans 
  Ferry 
  on 
  the 
  Mohawk 
  (Amsterdam 
  quad- 
  

   rangle) 
  the 
  displacement 
  is 
  estimated 
  by 
  Cumings 
  at 
  1300 
  feet 
  and 
  

   by 
  Prosser 
  at 
  1600 
  feet. 
  1 
  Near 
  the 
  north 
  edge 
  of 
  the 
  Amsterdam 
  

   quadrangle 
  the 
  fault 
  sends 
  off 
  two 
  branches 
  to 
  the 
  east, 
  each 
  of 
  

   which 
  takes 
  part 
  of 
  the 
  throw 
  of 
  the 
  main 
  fault. 
  These 
  two 
  

   branches, 
  called 
  by 
  Miller 
  the 
  West 
  Galway 
  and 
  East 
  Galway 
  faults, 
  

   continue 
  across 
  the 
  Broadalbin 
  quadrangle 
  on 
  to 
  Saratoga. 
  Across 
  

   Broadalbin, 
  Miller 
  estimates 
  the 
  throw 
  of 
  the 
  Hoffman 
  fault 
  as 
  

   but 
  250 
  feet, 
  but 
  states 
  that 
  this 
  rapidly 
  increases 
  in 
  its 
  course 
  across 
  

   the 
  Saratoga 
  quadrangle. 
  2 
  

  

  The 
  scarp 
  of 
  the 
  Hoffmans 
  fault 
  is 
  the 
  most 
  prominent 
  topo- 
  

   graphic 
  feature 
  of 
  the 
  Saratoga 
  region, 
  though 
  nearly 
  equalled 
  by 
  

   the 
  McGregor 
  scarp. 
  The 
  summit 
  knobs 
  of 
  the 
  range 
  reach 
  eleva- 
  

   tions 
  of 
  over 
  2000 
  feet, 
  towering 
  as 
  the 
  west 
  wall 
  of 
  the 
  Kaya- 
  

   derosseras 
  valley, 
  the 
  valley 
  floor 
  not 
  greatly 
  exceeding 
  600 
  feet 
  

   altitude. 
  None 
  but 
  Precambric 
  rocks 
  occur 
  west 
  of 
  the 
  fault 
  within 
  

   the 
  quadrangle 
  ; 
  but 
  east 
  of 
  it 
  such 
  heavy 
  drift 
  is 
  banked 
  up 
  against 
  

   the 
  face 
  of 
  the 
  fault 
  scarp 
  all 
  the 
  way 
  from 
  East 
  Galway 
  to 
  near 
  

   South 
  Corinth 
  that 
  no 
  rock 
  exposures 
  are 
  seen. 
  About 
  South 
  

   Corinth 
  Precambric 
  rocks 
  are 
  at 
  the 
  surface 
  east 
  of 
  the 
  fault; 
  

   about 
  East 
  Galway 
  rocks 
  of 
  the 
  Theresa 
  formation 
  are 
  at 
  the 
  sur- 
  

   face. 
  What 
  lies 
  between 
  the 
  two 
  is 
  chiefly 
  conjectural. 
  But 
  the 
  

   rapid 
  increase 
  in 
  prominence 
  of 
  the 
  fault 
  scarp 
  in 
  passing 
  north 
  

   from 
  East 
  Galway 
  can, 
  in 
  this 
  instance, 
  be 
  due 
  to 
  nothing 
  except 
  

   increasing 
  throw. 
  The 
  surface 
  of 
  the 
  western 
  block 
  is 
  tipped 
  to 
  

   the 
  south 
  more 
  than 
  that 
  of 
  the 
  eastern 
  block. 
  Back 
  from 
  Corinth 
  

   therefore 
  the 
  throw 
  is 
  equal 
  to 
  the 
  height 
  of 
  the 
  fault 
  scarp 
  plus 
  

   an 
  unknown 
  amount; 
  hence 
  Miller's 
  estimate 
  of 
  1000 
  feet 
  is 
  modest, 
  

   and 
  the 
  throw 
  is 
  likely 
  500 
  feet 
  in 
  excess 
  of 
  that. 
  

  

  To 
  recapitulate: 
  the 
  great 
  throw 
  of 
  the 
  Hoffmans 
  fault 
  at 
  Hoff- 
  

   mans 
  Ferry 
  is 
  split 
  into 
  three 
  parts 
  by 
  the 
  branching 
  of 
  the 
  fault 
  so 
  

   that, 
  across 
  the 
  Broadalbin 
  quadrangle, 
  the 
  main 
  fault 
  retains 
  only 
  

  

  1 
  In 
  vertical 
  faults 
  in 
  nearly 
  horizontal 
  rocks, 
  such 
  as 
  these, 
  the 
  displace- 
  

   ment 
  is 
  practically 
  all 
  throw, 
  so 
  far 
  as 
  can 
  be 
  told. 
  At 
  Hoffmans 
  Ferry 
  the 
  

   surface 
  beds 
  on 
  the 
  western, 
  or 
  upthrow, 
  side 
  of 
  the 
  fault 
  are 
  buried 
  under 
  

   a 
  thickness 
  of 
  from 
  1300 
  to 
  1600 
  feet 
  of 
  younger 
  rocks 
  on 
  the 
  opposite 
  side, 
  

   according 
  to 
  these 
  estimates. 
  Relatively 
  to 
  the 
  beds 
  on 
  the 
  western 
  side 
  the 
  

   corresponding 
  ones 
  on 
  the 
  east 
  have 
  been 
  vertically 
  dropped 
  by 
  that 
  amount. 
  

  

  2 
  N. 
  Y. 
  State 
  Mus. 
  Bui. 
  153, 
  p. 
  46. 
  

  

  