﻿114 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  Doctor 
  Ulrich 
  distinguishes 
  five 
  different 
  Eopaleozoic 
  troughs, 
  

   going 
  east 
  from 
  the 
  Adirondacks, 
  first, 
  the 
  Chazy 
  basin, 
  then 
  the 
  

   Levis 
  channel, 
  a 
  third 
  trough 
  which 
  contains 
  the 
  marble 
  forma- 
  

   tion 
  in 
  western 
  Vermont 
  and 
  succeeding 
  limestone 
  and 
  shale 
  for- 
  

   mations, 
  and 
  possibly 
  the 
  Lower 
  Cambric 
  (Georgian) 
  deposits. 
  

   The 
  fourth 
  trough 
  is 
  supposed 
  to 
  have 
  contained 
  the 
  Lower 
  Cam- 
  

   bric 
  deposits, 
  and 
  a 
  fifth 
  trough, 
  or 
  rather 
  set 
  of 
  troughs, 
  is 
  thought 
  

   to 
  be 
  indicated 
  by 
  the 
  highly 
  metamorphosed 
  Paleozoics 
  found 
  

   to 
  the 
  east 
  of 
  the 
  Lower 
  Cambric 
  outcrops. 
  The 
  evidence 
  on 
  

   which 
  Ulrich 
  bases 
  his 
  belief 
  in 
  the 
  existence 
  of 
  these 
  troughs 
  

   is 
  threefold: 
  (i) 
  the 
  differences 
  in 
  fossil 
  contents 
  of 
  the 
  sets 
  of 
  

   beds; 
  (2) 
  the 
  peculiarities 
  in 
  the 
  succession 
  of 
  the 
  various 
  gen- 
  

   eral 
  types 
  of 
  sediments; 
  and 
  (3) 
  the 
  physical 
  proof 
  of 
  excessive 
  

   folding 
  and 
  overthrusting. 
  

  

  We 
  have 
  in 
  the 
  two 
  sheets 
  here 
  described 
  undisputable 
  evi- 
  

   dence 
  of 
  at 
  least 
  two 
  parallel 
  troughs 
  in 
  the 
  two 
  entirely 
  differ- 
  

   ent 
  sets 
  of 
  formations 
  described 
  above. 
  These 
  are 
  the 
  lower 
  

   Mohawk 
  trough 
  in 
  the 
  west 
  and 
  the 
  Levis 
  trough 
  in 
  the 
  east. 
  

   If 
  the 
  Georgian 
  and 
  Bald 
  mountain 
  rocks 
  belong 
  to 
  the 
  third 
  or 
  

   fourth 
  trough, 
  this 
  is 
  also 
  represented 
  on 
  the 
  map. 
  We 
  have 
  here 
  

   considered 
  them 
  as 
  underlying 
  the 
  rocks 
  of 
  the 
  Levis 
  trough, 
  as 
  

   they 
  probably 
  do, 
  at 
  St 
  Albans 
  and 
  Georgia 
  in 
  Vermont 
  (see 
  Ulrich, 
  

   op. 
  cit.j 
  page 
  493). 
  It 
  can 
  not 
  be 
  doubted 
  that 
  the 
  present 
  posi- 
  

   tion 
  of 
  the 
  Georgian 
  beds 
  on 
  the 
  Schuylerville 
  sheet 
  above 
  the 
  

   graptolite 
  beds 
  of 
  the 
  Levis 
  channel, 
  and 
  again 
  the 
  position 
  of 
  the 
  

   latter 
  above 
  the 
  beds 
  of 
  the 
  Western 
  basin 
  require 
  for 
  the 
  

   explanation 
  of 
  this 
  complicated 
  reversed 
  position 
  under 
  the 
  as- 
  

   sumption 
  that 
  they 
  represent 
  but 
  two 
  troughs, 
  a 
  reversed 
  anti- 
  

   clinorium 
  with 
  axial 
  overthrust, 
  as 
  assumed 
  by 
  the 
  writer 
  in 
  a 
  

   former 
  publication 
  (Bulletin 
  42), 
  or 
  a 
  complicated 
  system 
  of 
  over- 
  

   thrusts 
  and 
  that 
  the 
  assumption 
  of 
  the 
  original 
  deposition 
  of 
  the 
  

   Georgian 
  beds 
  in 
  a 
  third 
  trough, 
  which 
  now 
  has 
  become 
  pushed 
  

   upon 
  the 
  second, 
  will 
  considerably 
  simplify 
  the 
  history 
  of 
  dias- 
  

   trophic 
  processes 
  which 
  have 
  led 
  to 
  the 
  present 
  structure 
  of 
  the 
  

   region. 
  

  

  The 
  cause 
  of 
  these 
  far-reaching 
  overthrust 
  phenomena 
  which 
  

   are 
  observed 
  in 
  the 
  whole 
  Appalachian 
  system 
  is 
  the 
  pressure 
  at- 
  

   tributed 
  to 
  deep-seated 
  " 
  suboceanic 
  spread 
  " 
  which 
  results 
  from 
  the 
  

   greater 
  density 
  of 
  the 
  terrestrial 
  crust 
  under 
  the 
  oceanic 
  basins, 
  

  

  