﻿GEOLOGY 
  OF 
  THOUSAND 
  ISLANDS 
  REGION 
  93 
  

  

  Ulrich 
  has 
  recently 
  made 
  the 
  important 
  discovery 
  of 
  an 
  uncon- 
  

   formity 
  between 
  these 
  beds 
  and 
  Division 
  A, 
  and 
  we 
  coincide 
  in 
  be- 
  

   lieving 
  that 
  this 
  division 
  is 
  properly 
  to 
  be 
  classed 
  with 
  the 
  beds 
  below 
  

   rather 
  than 
  with 
  the 
  Beekmantown. 
  The 
  Beekmantown 
  that 
  is 
  

   thinly 
  present 
  in 
  the 
  district 
  here 
  reported 
  upon 
  is 
  not 
  of 
  the 
  Cham- 
  

   plain 
  type, 
  but 
  of 
  the 
  Mohawk 
  valley 
  type, 
  lithologically 
  and 
  faunally 
  

   quite 
  like 
  the 
  beds 
  at 
  Little 
  Falls 
  and 
  thence 
  eastward 
  through 
  the 
  

   Mohawk 
  valley, 
  which 
  have 
  heretofore 
  been 
  called 
  the 
  " 
  fucoidal 
  

   beds," 
  and 
  which 
  we 
  are 
  proposing 
  to 
  call 
  the 
  Tribes 
  Hill 
  formation. 
  

   This 
  Beekmantown 
  did 
  not 
  come 
  into 
  this 
  northern 
  district 
  from 
  the 
  

   east 
  but 
  from 
  the 
  south, 
  and 
  so 
  far 
  as 
  we 
  know 
  did 
  not 
  extend 
  on 
  

   eastward. 
  But 
  in 
  passing 
  to 
  the 
  eastward, 
  beyond 
  the 
  limits 
  of 
  the 
  

   region 
  here 
  mapped, 
  Beekmantown 
  beds 
  begin 
  to 
  appear 
  above 
  the 
  

   Theresa, 
  and 
  in 
  our 
  belief 
  are 
  unconformable, 
  though 
  this 
  has 
  not 
  

   yet 
  been 
  demonstrated. 
  Also 
  in 
  our 
  belief 
  this 
  Beekmantown 
  is 
  not 
  

   representative 
  of 
  the 
  lower 
  portion 
  of 
  the 
  formation 
  but 
  of 
  the 
  upper 
  

   portion, 
  and 
  we 
  must 
  go 
  yet 
  farther 
  east 
  to 
  find 
  the 
  lower 
  beds 
  com- 
  

   ing 
  in 
  ; 
  while 
  the 
  thin 
  edge 
  of 
  Tribes 
  Hill 
  Beekmantow^n 
  in 
  our 
  dis- 
  

   trict 
  here 
  is 
  lowest 
  Beekmantown. 
  Following 
  a 
  condition 
  of 
  uplift 
  

   Beekmantown 
  submergence 
  seems 
  to 
  have 
  commenced 
  fairly 
  simul- 
  

   taneously 
  on 
  the 
  east, 
  west 
  and 
  south 
  sides 
  of 
  the 
  Adirondack 
  region. 
  

   Submergence 
  on 
  the 
  west 
  w^as 
  quickly 
  followed 
  by 
  emergence 
  due 
  to, 
  

   a 
  general 
  eastward 
  tilting 
  of 
  the 
  region, 
  so 
  that 
  at 
  Little 
  Falls 
  and 
  

   about 
  Theresa 
  only 
  a 
  slight 
  thickness 
  of 
  the 
  very 
  lowest 
  Beekman- 
  

   town 
  was 
  laid 
  down, 
  the 
  Tribes 
  Hill 
  formation. 
  This 
  formation 
  

   steadily 
  thickens 
  to 
  the 
  eastward, 
  along 
  the 
  Mohawk 
  valley, 
  though 
  

   apparently 
  representing 
  nothing 
  but 
  the 
  lowermost 
  Beekmantown. 
  

   The 
  chief 
  area 
  of 
  Beekmantown 
  sedimentation 
  in 
  New 
  York 
  was 
  the 
  

   Champlain 
  valley 
  trough 
  and 
  its 
  prolongation 
  southward. 
  Along 
  

   with 
  the 
  steady 
  subsidence 
  in 
  that 
  trough 
  seems 
  to 
  have 
  gone 
  a 
  sub- 
  

   sidence 
  of 
  the 
  St 
  Lawrence 
  trough 
  which, 
  like 
  the 
  previous 
  Potsdam 
  

   subsidence, 
  seems 
  to 
  have 
  commenced 
  at 
  the 
  east 
  and 
  worked 
  west- 
  

   ward 
  ; 
  so 
  that, 
  in 
  that 
  trough, 
  the 
  lowest 
  Beekmantown 
  is 
  absent, 
  and 
  

   steadily 
  higher 
  beds 
  are 
  at 
  the 
  base 
  going 
  west. 
  The 
  extreme 
  west- 
  

   ward 
  reach 
  of 
  this 
  Beekmantown 
  depression 
  of 
  the 
  St 
  Lawrence 
  

   trough 
  seems 
  never 
  to 
  have 
  reached 
  the 
  Theresa 
  district, 
  where 
  the 
  

   only 
  Beekmantown 
  represented 
  is 
  the 
  thin 
  base 
  of 
  the 
  Tribes 
  Hill 
  

   formation 
  of 
  the 
  Mohawk 
  Beekmantown 
  type. 
  Until 
  the 
  Beekman- 
  

   town 
  on 
  the 
  north 
  side 
  of 
  the 
  Adirondacks 
  has 
  received 
  more 
  

   thorough 
  study, 
  this 
  view 
  of 
  Beekmantown 
  conditions 
  in 
  the 
  St 
  Law- 
  

   rence 
  trough 
  can 
  not 
  be 
  regarded 
  as 
  based 
  on 
  sufficient 
  evidence, 
  

   though 
  evidence 
  on 
  the 
  other 
  three 
  sides 
  of 
  the 
  Adirondack 
  region 
  

  

  