﻿1 
  6 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  the 
  Paleozoic 
  rocks 
  of 
  the 
  Champlain 
  valley. 
  This 
  has 
  chiefly 
  

   expressed 
  itself 
  in 
  the 
  formation 
  of 
  a 
  great 
  number 
  of 
  normal 
  

   faults, 
  both 
  large 
  and 
  small. 
  The 
  Paleozoic 
  rocks 
  of 
  the 
  trough 
  

   are 
  but 
  little 
  folded 
  and 
  usually 
  but 
  slightly 
  tilted, 
  but 
  they 
  are 
  

   cut 
  into 
  great 
  slices 
  by 
  a 
  series 
  of 
  normal 
  faults 
  which 
  trend 
  about 
  

   north-northeast, 
  and 
  which 
  are 
  themselves 
  broken 
  by 
  occasional 
  

   cross 
  faults. 
  Most 
  of 
  these 
  faults 
  downthrow 
  to 
  -the 
  east, 
  but 
  at 
  

   the 
  same 
  time 
  the 
  upthrow 
  side 
  is 
  given 
  a 
  tilt 
  to 
  the 
  west, 
  forming 
  

   a 
  valley 
  when 
  combined 
  with 
  the 
  upthrow 
  side 
  of 
  the 
  next 
  fault 
  

   to 
  the 
  west. 
  Occasional 
  faults 
  throw 
  to 
  the 
  west, 
  with 
  the 
  result 
  

   that 
  a 
  depressed 
  structural 
  valley 
  called 
  a 
  graben 
  is 
  formed. 
  

  

  The 
  drop 
  from 
  the 
  level 
  of 
  the 
  Adirondack 
  highland 
  to 
  the 
  low 
  

   grounds 
  of 
  the 
  Mohawk 
  trough 
  is 
  produced 
  by 
  a 
  series 
  of 
  these 
  

   great 
  faults, 
  all 
  throwing 
  to 
  the 
  east. 
  

  

  Passing 
  from 
  the 
  Mohawk 
  rocks 
  to 
  those 
  of 
  the 
  more 
  easterly 
  

   troughs, 
  one 
  finds 
  a 
  quite 
  different 
  kind 
  of 
  structures. 
  In 
  the 
  

   first 
  place 
  the 
  rocks 
  are 
  much 
  more 
  folded. 
  The 
  chief 
  structures 
  

   here 
  are 
  also 
  faults, 
  but 
  instead 
  of 
  being 
  nearly 
  vertical 
  and 
  normal, 
  

   they 
  are 
  quite 
  flat 
  and 
  are 
  overthrusts, 
  along 
  which 
  great 
  masses 
  of 
  

   rock 
  have 
  been 
  pushed 
  westward 
  for 
  miles. 
  Unlike 
  the 
  Mohawk 
  

   rocks, 
  they 
  now 
  lie 
  far 
  from 
  the 
  area 
  where 
  they 
  were 
  originally 
  

   deposited 
  and 
  form 
  a 
  jumble 
  of 
  overthrust 
  masses. 
  Their 
  structure 
  

   is 
  exceedingly, 
  often 
  hopelessly, 
  complicated. 
  

  

  DESCRIPTIVE 
  GEOLOGY 
  

  

  BY 
  H. 
  P. 
  CUSHING 
  

  

  The 
  exposed 
  rocks 
  of 
  the 
  two 
  quadrangles 
  are 
  of 
  Precambric, 
  

   Cambric 
  and 
  Ordovicic 
  age, 
  together 
  with 
  the 
  unconsolidated 
  

   deposits 
  of 
  Quaternary 
  age 
  and 
  the 
  small 
  exposure 
  of 
  extrusive 
  

   rock 
  of 
  unknown 
  age 
  north 
  of 
  Schuylerville. 
  

  

  PRECAMBRIC 
  ROCKS 
  

   The 
  Precambric 
  rocks 
  of 
  the 
  Adirondack 
  region, 
  so 
  far 
  as 
  

   known, 
  are 
  comprised 
  in 
  an 
  old 
  series 
  of 
  sedimentary 
  rocks, 
  

   named 
  the 
  Grenville 
  series, 
  which 
  are 
  the 
  oldest 
  known 
  rocks 
  of 
  

   the 
  district, 
  and 
  in 
  various 
  masses 
  of 
  igneous 
  rocks 
  all 
  of 
  which 
  

   cut 
  the 
  Grenville 
  rocks 
  intrusively 
  and 
  are 
  therefore 
  younger. 
  The 
  

   oldest 
  of 
  these 
  igneous 
  rocks 
  is 
  a 
  granite 
  called 
  the 
  Laurentian. 
  

   Later 
  than 
  this 
  came 
  a 
  series 
  of 
  intrusions, 
  anorthosite, 
  syenite, 
  

  

  