﻿ADIRONDACK 
  MAGNETIC 
  IRON 
  ORES 
  II 
  

  

  region 
  are 
  now 
  fairly 
  well 
  defined. 
  Professor 
  Kemp 
  has 
  worked 
  in 
  

   the 
  eastern 
  section 
  including 
  Essex, 
  Warren, 
  and 
  Washington 
  

   counties 
  and 
  adjacent 
  territory. 
  Professor 
  Cushing 
  has 
  been 
  

   mainly 
  occupied 
  with 
  the 
  northern 
  region 
  of 
  Clinton, 
  Franklin 
  and 
  

   Hamilton 
  counties; 
  while 
  Professor 
  Smyth 
  has 
  worked 
  in 
  St 
  Law- 
  

   rence, 
  Jefferson 
  and 
  Lewis 
  counties 
  on 
  the 
  western 
  side. 
  

  

  With 
  the 
  publication 
  of 
  topographic 
  sheets 
  for 
  parts 
  of 
  the 
  region 
  

   by 
  the 
  United 
  States 
  Geological 
  Survey 
  in 
  cooperation 
  with 
  the 
  

   State 
  Engineer 
  it 
  has 
  been 
  possible 
  recently 
  to 
  undertake 
  the 
  

   preparation 
  of 
  detailed 
  geologic 
  maps. 
  Thus 
  far 
  Professor 
  Cushing 
  

   has 
  reported 
  upon 
  the 
  geology 
  of 
  the 
  Little 
  Falls 
  quadrangle 
  in 
  

   Herkimer 
  county 
  and 
  the 
  Long 
  Lake 
  quadrangle 
  in 
  Hamilton 
  

   county 
  and 
  Dr 
  I. 
  H. 
  Ogilvie 
  has 
  surveyed 
  and 
  described 
  the 
  Para- 
  

   dox 
  Lake 
  quadrangle 
  in 
  Essex 
  county. 
  Field 
  work 
  has 
  been 
  

   completed 
  also 
  upon 
  one 
  or 
  more 
  quadrangles 
  in 
  Essex, 
  Hamilton 
  

   and 
  St 
  Lawrence 
  counties. 
  

  

  Outline 
  of 
  geology 
  

  

  The 
  rocks 
  comprising 
  the 
  Adirondack 
  region 
  are 
  almost 
  exclu- 
  

   sively 
  Precambric 
  in 
  age. 
  The 
  bordering 
  Paleozoic 
  strata 
  are 
  

   sometimes 
  found 
  well 
  within 
  the 
  interior, 
  but 
  they 
  occur 
  in 
  discon- 
  

   nected 
  exposures 
  which 
  altogether 
  comprise 
  an 
  inconsiderable 
  

   portion 
  of 
  the 
  total 
  area. 
  Their 
  base, 
  the 
  Potsdam 
  sandstone, 
  

   rests 
  unconformably 
  upon 
  the 
  Precambric 
  crystalline 
  rocks. 
  The 
  

   unconformity 
  marks 
  a 
  very 
  long 
  time 
  gap. 
  Before 
  the 
  depo- 
  

   sition 
  of 
  the 
  Potsdam 
  the 
  Precambric 
  rocks 
  had 
  been 
  modified 
  by 
  

   repeated 
  dynamic 
  action, 
  had 
  been 
  uplifted, 
  intruded, 
  and 
  finally 
  

   exposed 
  to 
  erosive 
  influences 
  that 
  removed 
  great 
  thicknesses 
  from 
  

   their 
  surface. 
  

  

  The 
  Precambric 
  rocks, 
  with 
  the 
  exception 
  of 
  small 
  dikes 
  that 
  were 
  

   of 
  late 
  Precambric 
  intrusion, 
  have 
  all 
  been 
  subjected 
  to 
  powerful 
  

   compression 
  and 
  in 
  many 
  cases 
  have 
  been 
  greatly 
  changed 
  by 
  

   metamorphism. 
  Among 
  them 
  there 
  are 
  representatives 
  which 
  

   were 
  undoubtedly 
  original 
  sediments, 
  but 
  these 
  have 
  almost 
  wholly 
  

   lost 
  the 
  characteristic 
  features 
  of 
  such 
  rocks 
  so 
  that 
  their 
  recognition 
  

   is 
  at 
  times 
  a 
  matter 
  of 
  extreme 
  difficulty, 
  if 
  indeed 
  they 
  can 
  now 
  

   be 
  identified 
  at 
  all. 
  The 
  metamorphism 
  took 
  place 
  while 
  they 
  were 
  

   deeply 
  buried, 
  under 
  conditions 
  of 
  pressure 
  and 
  heat 
  that 
  brought 
  

   about 
  a 
  recrystallization 
  of 
  the 
  fragmental 
  components 
  ; 
  and 
  what 
  

   were 
  once 
  sandstones, 
  shales 
  and 
  calcareous 
  sediments 
  now 
  have 
  the 
  

   characters 
  of 
  gneisses, 
  schists 
  and 
  coarsely 
  crystalline 
  limestones. 
  

  

  