﻿GEOLOGY 
  OF 
  THE 
  NORTH 
  CREEK 
  QUADRANGLE 
  5 
  1 
  

  

  Moon-Hackensack 
  mountain 
  fault. 
  This 
  is 
  a 
  well-defined 
  fault 
  

   whose 
  presence 
  is 
  proved 
  by 
  most 
  of 
  the 
  criteria 
  generally 
  appli- 
  

   cable 
  in 
  this 
  region. 
  The 
  strike 
  is 
  northwest-southeast 
  and 
  in 
  per- 
  

   fect 
  harmony 
  with 
  that 
  of 
  Moon 
  and 
  Hackensack 
  mountains. 
  The 
  

   trend 
  of 
  the 
  fault 
  scarp 
  is 
  clearly 
  marked 
  by 
  the 
  topography, 
  the 
  

   western 
  face 
  of 
  Moon 
  mountain 
  being 
  especially 
  high 
  and 
  steep 
  

   (see 
  plate 
  9). 
  Between 
  the 
  two 
  mountains 
  the 
  scarp 
  is 
  lowest 
  

   because 
  the 
  weaker 
  Grenville 
  there 
  has 
  been 
  worn 
  down 
  most 
  

   rapidly. 
  This 
  whole 
  earth 
  block 
  shows 
  the 
  eastward 
  downtilt, 
  

   particularly 
  in 
  the 
  case 
  of 
  Moon 
  mountain. 
  In 
  a 
  large 
  prospect 
  

   hole 
  at 
  the 
  western 
  base 
  of 
  Hackensack 
  mountain 
  and 
  close 
  to 
  the 
  

   road 
  there 
  is 
  much 
  evidence 
  of 
  shearing 
  along 
  the 
  fault. 
  Near 
  

   the 
  source 
  of 
  the 
  small 
  stream 
  along 
  the 
  fault 
  and 
  half 
  way 
  between 
  

   the 
  mountains 
  there 
  is 
  a 
  fine 
  exhibition 
  of 
  crushed 
  and 
  brecciated 
  

   Grenville 
  gneiss. 
  Sheared 
  rock 
  was 
  also 
  noted 
  along 
  the 
  western 
  

   side 
  of 
  Moon 
  mountain. 
  The 
  maximum 
  throw 
  of 
  this 
  fault 
  appears 
  

   to 
  have 
  been 
  no 
  less 
  than 
  600 
  feet. 
  

  

  County 
  House 
  mountain 
  fault. 
  This 
  fault 
  is 
  shown 
  dotted 
  on 
  

   the 
  map 
  because 
  its 
  presence 
  is 
  not 
  altogether 
  certain. 
  The 
  steep 
  

   eastern 
  front 
  of 
  the 
  County 
  House-Kelm 
  mountain 
  masses 
  and 
  

   the 
  fact 
  that 
  the 
  Grenville 
  (much 
  limestone) 
  comes 
  in 
  rather 
  

   sharply 
  against 
  the 
  bases 
  of 
  these 
  mountains 
  are 
  the 
  principal 
  evi- 
  

   dences 
  for 
  the 
  faulting. 
  The 
  Grenville 
  here, 
  contrary 
  to 
  the 
  usual 
  

   thing, 
  either 
  dips 
  away 
  from 
  the 
  fault 
  or 
  its 
  strike 
  is 
  at 
  high 
  angles 
  

   against 
  the 
  fault. 
  

  

  Kelm 
  mountain 
  fault. 
  This 
  is 
  a 
  good 
  example 
  of 
  a 
  fault 
  wholly 
  

   within 
  a 
  mass 
  of 
  very 
  homogeneous, 
  igneous 
  rock. 
  The 
  fault 
  scarp 
  

   is 
  much 
  more 
  in 
  evidence 
  than 
  the 
  contour 
  lines 
  suggest, 
  and 
  there 
  

   is 
  a 
  rather 
  distinct 
  eastward 
  downtilt 
  of 
  the 
  block. 
  Shear 
  zones 
  

   were 
  noted 
  in 
  two 
  or 
  three 
  places. 
  The 
  displacement 
  is 
  as 
  much 
  

   as 
  300 
  feet. 
  

  

  Millington 
  brook 
  fault. 
  This 
  fault 
  lies 
  along 
  the 
  eastern 
  side 
  

   of 
  the 
  valley 
  of 
  Millington 
  brook 
  and 
  strikes 
  north-northwest 
  by 
  

   south-southeast. 
  Where 
  it 
  crosses 
  the 
  road, 
  1% 
  miles 
  south- 
  

   west 
  of 
  Kelm 
  pond, 
  the 
  rocks 
  are 
  considerably 
  sheared 
  and 
  

   brecciated. 
  On 
  the 
  western 
  side 
  of 
  the 
  small 
  mountain 
  (1302 
  

   feet), 
  near 
  the 
  north 
  end 
  of 
  the 
  fault, 
  sheared 
  rock 
  was 
  also 
  noted. 
  

   The 
  extension 
  of 
  this 
  fault 
  southward 
  to 
  the 
  western 
  base 
  of 
  County 
  

   House 
  mountain 
  is 
  somewhat 
  doubtful 
  though 
  the 
  relations 
  of 
  the 
  

   rock 
  masses 
  and 
  the 
  topography 
  strongly 
  suggest 
  it. 
  The 
  throw 
  

   of 
  this 
  fault 
  is 
  probably 
  not 
  over 
  a 
  few 
  hundred 
  feet. 
  

  

  