﻿REPORT 
  OF 
  THE 
  DIRECTOR 
  I912 
  8l 
  

  

  CAMBRIC 
  PHYSIOGRAPHY 
  

  

  The 
  Cambric 
  peneplain. 
  As 
  is 
  well 
  known, 
  the 
  whole 
  Adiron- 
  

   dack 
  region 
  was 
  above 
  water 
  and 
  undergoing 
  erosion 
  during 
  the 
  

   early 
  and 
  middle 
  Cambric. 
  This 
  is 
  proved 
  by 
  the 
  total 
  absence 
  

   of 
  the 
  early 
  and 
  middle 
  Cambric 
  strata 
  and 
  also 
  because 
  there 
  

   is 
  not 
  the 
  slightest 
  evidence 
  that 
  any 
  such 
  strata 
  ever 
  were 
  

   deposited 
  over 
  the 
  region. 
  Furthermore 
  there 
  is 
  every 
  reason 
  

   to 
  believe 
  that 
  this 
  important 
  erosion 
  interval 
  was 
  inaugurated 
  

   long 
  before 
  the 
  opening 
  of 
  the 
  Paleozoic 
  era. 
  As 
  a 
  result 
  of 
  

   this 
  vast 
  erosion 
  the 
  whole 
  Adirondack 
  region 
  had, 
  by 
  the 
  open- 
  

   ing 
  of 
  Potsdam 
  (late 
  Cambric) 
  time, 
  become 
  worn 
  down 
  to 
  the 
  

   condition 
  of 
  a 
  more 
  or 
  less 
  well-developed 
  peneplain. 
  

  

  As 
  will 
  be 
  shown 
  below, 
  the 
  distribution 
  of 
  the 
  strata 
  proves 
  

   that 
  the 
  northeastern 
  and 
  eastern 
  borders 
  of 
  the 
  Adirondacks 
  

   sank 
  below 
  sea 
  level 
  first 
  in 
  early 
  Potsdam 
  time; 
  then 
  the 
  south- 
  

   eastern 
  and 
  southern 
  portions 
  in 
  late 
  Potsdam, 
  Theresa 
  and 
  

   Little 
  Falls 
  times 
  ; 
  and 
  last 
  the 
  southwestern 
  border 
  well 
  along 
  

   in 
  Ordovicic 
  (Pamelia) 
  time. 
  

  

  The 
  peneplain 
  surface 
  of 
  the 
  Precambric 
  rock 
  under 
  the 
  Paleo- 
  

   zoic 
  strata 
  has 
  been 
  carefully 
  studied 
  on 
  all 
  sides 
  of 
  the 
  Adiron- 
  

   dacks 
  and 
  it 
  has 
  been 
  fully 
  demonstrated 
  that 
  it 
  is 
  roughest 
  

   along 
  the 
  northeastern 
  and 
  eastern 
  sides 
  ; 
  less 
  rough 
  along 
  the 
  

   southeastern 
  and 
  southern 
  sides 
  ; 
  and 
  very 
  smooth 
  along 
  the 
  

   southwestern 
  side. 
  Even 
  where 
  roughest 
  the 
  differences 
  of 
  

   elevation 
  never 
  amount 
  to 
  more 
  than 
  a 
  few 
  hundred 
  feet, 
  while 
  

   on 
  the 
  southern 
  side 
  Cushing 
  2 
  and 
  the 
  writer 
  10 
  have 
  each 
  found 
  

   knobs 
  or 
  ridges 
  of 
  hard 
  Precambric 
  rock 
  projecting 
  upward 
  from 
  

   fifty 
  to 
  eighty 
  feet 
  into 
  the 
  Cambric 
  strata, 
  though 
  these 
  appear 
  

   to 
  be 
  extreme 
  cases 
  of 
  ruggedness 
  of 
  the 
  surface 
  of 
  the 
  pene- 
  

   plain. 
  Along 
  the 
  southwestern 
  border 
  of 
  the 
  Adirondacks 
  the 
  

   writer 
  has 
  shown 
  by 
  his 
  mapping 
  of 
  the 
  Port 
  Leyden 
  quad- 
  

   rangle 
  9 
  that 
  the 
  surface 
  of 
  the. 
  peneplain 
  is 
  there 
  remarkably 
  

   smooth. 
  This 
  increasing 
  smoothness 
  of 
  the 
  peneplain 
  from 
  

   northeast 
  to 
  southwest 
  is 
  precisely 
  what 
  would 
  be 
  expected 
  

   because 
  the 
  southwestern 
  side 
  of 
  the 
  Adirondacks 
  remained 
  dry 
  

   land 
  much 
  the 
  longest 
  time. 
  In 
  the 
  eastern 
  Adirondacks 
  Kemp 
  6 
  

  

  2 
  Page 
  57-58. 
  The 
  footnote 
  numbers 
  refer 
  to 
  the 
  numbered 
  references 
  

   given 
  in 
  the 
  list 
  at 
  the 
  end 
  of 
  this 
  paper. 
  

   10 
  Page 
  si. 
  

   9 
  Pages 
  40-41. 
  

   6 
  Pages 
  408-12. 
  

  

  