﻿GEOLOGY 
  OF 
  THE 
  NORTH 
  CREEK 
  QUADRANGLE 
  ^7 
  

  

  side 
  of 
  the 
  south 
  end 
  of 
  Schroon 
  lake 
  and 
  thence 
  southward 
  to 
  the 
  

   north 
  end 
  of 
  Loon 
  lake. 
  At 
  two 
  places 
  along 
  Schroon 
  lake 
  the 
  

   fairly 
  steep 
  scarp 
  rises 
  fully 
  400 
  feet. 
  The 
  southern 
  end 
  of 
  the 
  

   fault 
  block 
  is 
  a 
  mass 
  of 
  Grenville 
  (chiefly 
  quartzite) 
  whose 
  bold 
  

   scarp 
  at 
  one 
  place 
  rises 
  400 
  feet. 
  The 
  whole 
  fault 
  block, 
  especially 
  

   the 
  southern 
  part, 
  shows 
  the 
  usual 
  downslope 
  toward 
  the 
  east. 
  

   This 
  scarp 
  strikes 
  at 
  a 
  high 
  angle 
  across 
  the 
  foliation 
  bands 
  and 
  

   hence 
  it 
  is 
  difficult 
  to 
  account 
  for 
  except 
  on 
  the 
  basis 
  of 
  faulting. 
  

  

  A 
  smaller 
  fault 
  along 
  the 
  western 
  side 
  of 
  the 
  southern 
  end 
  of 
  

   Schroon 
  lake 
  has 
  a 
  prominent 
  scarp 
  rising 
  some 
  300 
  to 
  400 
  feet. 
  

   Where 
  it 
  cuts 
  across 
  the 
  gabbro 
  stock 
  near 
  the 
  map 
  edge 
  the 
  fault 
  

   scarp 
  rises 
  as 
  a 
  high 
  vertical 
  wall 
  along 
  which 
  the 
  rock 
  is 
  unusually 
  

   soft 
  and 
  weathered 
  and 
  evidently 
  sheared. 
  

  

  Loon 
  Lake 
  mountain 
  fault. 
  The 
  short 
  fault 
  shown 
  on 
  the 
  map 
  

   just 
  east 
  of 
  the 
  north 
  end 
  of 
  Loon 
  lake 
  and 
  at 
  the 
  base 
  of 
  Loon 
  

   Lake 
  mountain 
  is 
  one 
  of 
  special 
  interest. 
  Here 
  again 
  the 
  contours 
  

   are 
  not 
  close 
  enough 
  together 
  since 
  the 
  fault 
  scarp 
  which 
  rises 
  to 
  

   a 
  height 
  of 
  700 
  feet 
  is 
  very 
  steep, 
  the 
  upper 
  300 
  or 
  400 
  feet 
  being 
  

   a 
  sheer 
  precipice. 
  We 
  have 
  here 
  at 
  once 
  the 
  highest 
  steep 
  ledge 
  

   of 
  Grenville 
  and 
  the 
  finest 
  example 
  of 
  a 
  practically 
  unaltered 
  fault' 
  

   clifT 
  within 
  the 
  quadrangle 
  (see 
  plate 
  10). 
  The 
  upper 
  portion 
  of 
  

   the 
  cliff 
  consists 
  of 
  quartzite 
  in 
  thin 
  to 
  thick 
  beds 
  with 
  low 
  north- 
  

   easterly 
  dip 
  so 
  that 
  the 
  truncated 
  edges 
  of 
  the 
  quartzite 
  layers 
  are 
  

   distinctly 
  visible 
  in 
  the 
  face 
  of 
  the 
  cliff. 
  The 
  less 
  steep 
  scarp 
  

   forming 
  the 
  western 
  face 
  of 
  this 
  fault 
  block 
  as 
  well 
  as 
  its 
  down- 
  

   tilt 
  toward 
  the 
  east 
  are 
  due 
  to 
  the 
  Schroon 
  lake 
  fault 
  already 
  de- 
  

   scribed. 
  Plate 
  it 
  gives 
  a 
  good 
  idea 
  of 
  the 
  appearance 
  of 
  this 
  fault 
  

   block 
  mountain. 
  

  

  Other 
  faults. 
  The 
  small 
  fault 
  north 
  of 
  Valentine 
  pond 
  strikes 
  

   due 
  north 
  and 
  south 
  and 
  shows 
  a 
  prominent 
  scarp 
  near 
  its 
  north 
  

   end. 
  The 
  contours 
  are 
  not 
  close 
  enough 
  together 
  on 
  the 
  mountain 
  

   side 
  since 
  the 
  wall 
  of 
  rock, 
  which 
  rises 
  fully 
  600 
  feet, 
  is 
  very 
  steep 
  

   to 
  actually 
  vertical 
  in 
  places. 
  Hard, 
  distinctly 
  banded 
  Grenville 
  

   gneiss 
  makes 
  up 
  the 
  upper 
  three-fourths 
  of 
  the 
  wall 
  and 
  rests 
  upon 
  

   granite. 
  The 
  fault 
  has 
  broken 
  sharply 
  across 
  the 
  strike 
  of 
  the 
  

   foliation 
  of 
  both 
  the 
  Grenville 
  and 
  granite. 
  

  

  As 
  judged 
  wholly 
  by 
  the 
  topography, 
  there 
  appears 
  to 
  be 
  a 
  con- 
  

   siderable 
  fault 
  block 
  just 
  west 
  of 
  Loon 
  lake. 
  The 
  fault 
  and 
  its 
  

   scarp 
  lie 
  from 
  1 
  to 
  1/2 
  miles 
  west 
  of 
  the 
  lake 
  and 
  the 
  downtilt 
  

   toward 
  the 
  lake 
  is 
  very 
  noticeable. 
  

  

  The 
  shape 
  of 
  the 
  lake 
  basin 
  and 
  character 
  of 
  the 
  topography 
  

   suggest 
  the 
  presence 
  of 
  a 
  fault 
  along 
  the 
  west 
  side 
  of 
  Friends 
  lake. 
  

  

  