﻿20 
  NKVV 
  YORK 
  STATE 
  MUSEUM 
  

  

  Small 
  areas 
  of 
  the 
  sediments 
  occur 
  in 
  the 
  interior 
  as 
  far 
  as 
  40 
  miles 
  

   from 
  the 
  borders. 
  In 
  some 
  instances 
  they 
  lie 
  1500 
  feet 
  above 
  sea 
  

   level. 
  They 
  represent 
  mere 
  remnants 
  of 
  once 
  continuous 
  deposits 
  

   which 
  extended 
  over 
  most 
  if 
  not 
  all 
  of 
  the 
  Adirondacks. 
  There 
  is 
  

   strong 
  evidence 
  that 
  the 
  submergence 
  of 
  the 
  region 
  was 
  practically 
  

   complete 
  during 
  Utica 
  time. 
  Since 
  the 
  close 
  of 
  that 
  epoch 
  the 
  

   region 
  has 
  been 
  above 
  sea 
  level, 
  exposed 
  to 
  weathering 
  and 
  erosion, 
  

   and 
  has 
  received 
  no 
  deposits 
  except 
  the 
  sands, 
  gravels 
  and 
  clays 
  

   left 
  by 
  the 
  glacial 
  invasion 
  and 
  the 
  more 
  recent 
  river 
  detritus. 
  

  

  Structural 
  features. 
  The 
  structures 
  of 
  the 
  Precambric 
  rocks 
  as 
  

   revealed 
  by 
  their 
  present 
  attitudes 
  in 
  the 
  field 
  have 
  not 
  been 
  worked 
  

   out 
  for 
  the 
  Adirondack 
  region, 
  and 
  even 
  over 
  the 
  limited 
  areas 
  that 
  

   have 
  been 
  studied 
  and 
  mapped 
  with 
  care 
  the 
  structural 
  details 
  in 
  

   most 
  cases 
  have 
  proved 
  too 
  confusing 
  to 
  be 
  deciphered. 
  There 
  is 
  

   abundant 
  proof, 
  however, 
  that 
  the 
  rocks 
  have 
  undergone 
  great 
  

   compression 
  and 
  have 
  been 
  folded 
  and 
  faulted 
  on 
  an 
  extensive 
  scale. 
  

  

  One 
  of 
  the 
  principal 
  difficulties 
  encountered 
  in 
  the 
  study 
  of 
  the 
  

   structural 
  features 
  is 
  the 
  extreme 
  variability 
  as 
  to 
  the 
  evidences 
  

   afforded 
  by 
  the 
  rocks 
  of 
  their 
  disturbance. 
  The 
  presence 
  of 
  foliated 
  

   and 
  gneissoid 
  textures 
  is 
  a 
  common 
  characteristic 
  but 
  they 
  are 
  not 
  

   always 
  so 
  apparent 
  as 
  to 
  be 
  a 
  serviceable 
  guide 
  in 
  the 
  field. 
  

  

  Foliation 
  is 
  best 
  developed 
  in 
  the 
  dark 
  sedimentary 
  gneisses 
  and 
  

   schists. 
  These 
  rocks 
  contain 
  a 
  considerable 
  proportion 
  of 
  the 
  ferro- 
  

   magnesian 
  silicates 
  — 
  biotite, 
  hornblende 
  and 
  pyroxene 
  — 
  which 
  

   owing 
  to 
  their 
  crystal 
  habit 
  would 
  orient 
  themselves 
  most 
  readily 
  

   under 
  compression. 
  When 
  the 
  foliation 
  is 
  parallel 
  to 
  the 
  original 
  

   bedding 
  planes, 
  as 
  seems 
  to 
  be 
  the 
  general 
  case 
  with 
  these 
  rocks, 
  the 
  

   records 
  of 
  dips 
  and 
  strikes 
  afford 
  unquestionable 
  evidence 
  for 
  estab- 
  

   lishing 
  the 
  structure. 
  The 
  limestones 
  have 
  flowed 
  and 
  recrystal- 
  

   lized 
  so 
  that 
  they 
  rarely 
  show 
  either 
  foliation 
  or 
  traces 
  of 
  their 
  

   former 
  bedded 
  structure. 
  

  

  In 
  areas 
  underlain 
  by 
  a 
  complex 
  of 
  igneous 
  and 
  sedimentary 
  

   formations 
  it 
  is 
  seldom 
  that 
  any 
  connected 
  series 
  of 
  dip 
  and 
  strike 
  

   observations 
  can 
  be 
  made. 
  There 
  is 
  some 
  possibility 
  that 
  in 
  the 
  

   districts 
  composed 
  mainly 
  of 
  the 
  Grenville 
  series, 
  such 
  as 
  on 
  the 
  

   west 
  and 
  south, 
  a 
  close 
  study 
  of 
  the 
  field 
  relations 
  may 
  yield 
  positive 
  

   results. 
  

  

  The 
  strikes 
  and 
  dips 
  in 
  any 
  part 
  of 
  the 
  region 
  seldom 
  remain 
  

   uniform 
  over 
  more 
  than 
  a 
  small 
  area. 
  The 
  strike 
  generally 
  follows 
  

   more 
  or 
  less 
  closely 
  the 
  prevailing 
  trend 
  of 
  the 
  ridges, 
  that 
  is 
  in 
  a 
  

   direction 
  east 
  of 
  north, 
  but 
  it 
  is 
  subject 
  to 
  local 
  variations 
  of 
  several 
  

   degrees. 
  The 
  swings 
  are 
  gradual 
  as 
  would 
  be 
  expected 
  in 
  folded 
  

  

  