﻿FIFTH 
  REPORT 
  OF 
  THE 
  DIRECTOR 
  IQOS 
  

  

  167 
  

  

  Adirondack 
  Precambrics 
  under 
  the 
  Potsdam 
  formation, 
  by 
  rocks 
  

   of 
  the 
  same 
  kind. 
  

  

  Some 
  most 
  interesting 
  examples 
  of 
  the 
  style 
  of 
  inliers 
  last 
  men- 
  

   tioned 
  .are 
  observed 
  in 
  the 
  Little 
  Falls 
  sheet, 
  mapped 
  by 
  Professor 
  

   Gushing. 
  We 
  here 
  especially 
  note 
  

   the 
  Middleville 
  inlier 
  [see 
  text 
  

   fig. 
  3, 
  4]. 
  This 
  is 
  an 
  outcrop 
  of 
  

   syenite 
  rocks 
  in 
  the 
  bottom 
  of 
  the 
  

   deep 
  valley 
  of 
  West 
  Canada 
  creek. 
  

   Although 
  it 
  is 
  obvious 
  that 
  the 
  cor- 
  

   rasion 
  by 
  the 
  river 
  is 
  the 
  fi.nal 
  

   cause 
  of 
  the 
  exposure 
  of 
  this 
  rock 
  

   mass, 
  it 
  follows 
  also 
  from 
  the 
  ab- 
  

   sence 
  of 
  exposures 
  of 
  the 
  same 
  

   rock 
  farther 
  up 
  and 
  down 
  the 
  

   valley, 
  that 
  the 
  syenite 
  here 
  pro- 
  

   trudes 
  into 
  the 
  overlying 
  and 
  

   surrounding 
  Beekmantown 
  beds 
  in 
  

  

  Inlier 
  

  

  Adirondack 
  ;?. 
  ^5^^.^^^^°^" 
  limestone 
  1 
  

  

  Middleville, 
  N.Y. 
  Scale 
  i 
  m. 
  

   in. 
  

  

  000 
  

   000 
  

  

  consequence 
  of 
  the 
  irregularity 
  of 
  ^^^- 
  3 
  

  

  the 
  surface 
  of 
  the 
  

  

  plateau 
  OA'er 
  which 
  the 
  Beekman- 
  = 
  ^ 
  " 
  

  

  town 
  sea 
  advanced. 
  The 
  syenite 
  i"s 
  of 
  the 
  same 
  age 
  as 
  the 
  other 
  

  

  syenite 
  intrusions 
  associated 
  with 
  the 
  Grenville 
  series 
  of 
  the 
  Adiron- 
  

  

  dacks 
  and 
  a 
  portion 
  of 
  the 
  Adirondack 
  massive. 
  Underground 
  it 
  is 
  

  

  Fig. 
  

  

  Section 
  of 
  inlier 
  at 
  Middleville, 
  N. 
  Y. 
  

  

  /\ 
  y\ 
  y\ 
  

  

  Precambric 
  

  

  

  Beekmantown 
  

  

  connected 
  with 
  the 
  larger 
  and 
  better 
  known 
  Little 
  Falls 
  inlier 
  con- 
  

   sisting 
  of 
  a 
  like 
  syenite. 
  Since 
  the 
  latter, 
  however, 
  is 
  much 
  involved 
  

   in 
  strong 
  faults 
  and 
  obviously 
  owes 
  much 
  of 
  its 
  prominence 
  to 
  

   " 
  horst 
  '' 
  structure, 
  we 
  will 
  mention 
  it 
  more 
  fully 
  under 
  that 
  

   caption. 
  

  

  A 
  much 
  smaller 
  group 
  of 
  inliers 
  of 
  Precambric 
  rocks 
  in 
  the 
  Pots- 
  

   dam 
  sandstone 
  similar 
  to 
  those 
  on 
  the 
  northwest 
  and 
  north 
  side 
  of 
  

   the 
  Adirondacks, 
  is 
  also 
  found 
  on 
  the 
  east 
  side, 
  about 
  Port 
  Henry. 
  

   The 
  Potsdam 
  there 
  rests 
  as 
  a 
  thin 
  veneer 
  on 
  a 
  steeply 
  tilted 
  fault 
  

   block 
  and 
  in 
  several 
  places 
  knolls 
  of 
  Precambric 
  rocks 
  «vhich 
  

   clearly 
  were 
  once 
  small 
  islands 
  in 
  the 
  shallow 
  Potsdam 
  sea, 
  project 
  

   above 
  the 
  much 
  eroded 
  Potsdam 
  beds 
  [see 
  text 
  fig. 
  5]. 
  

  

  