﻿9° 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  the 
  grit 
  at 
  the 
  base 
  were 
  it 
  not 
  for 
  the 
  fact 
  that 
  it 
  is 
  not 
  always 
  

   in 
  contact 
  with 
  the 
  Georgian. 
  But 
  this 
  fact, 
  since 
  we 
  now 
  know 
  

   that 
  the 
  Georgian 
  and 
  the 
  Ordovicic 
  are 
  in 
  many, 
  or 
  all, 
  places 
  

   separated 
  by 
  an 
  overthrust 
  plane, 
  is 
  no 
  longer 
  of 
  decisive 
  value. 
  

   On 
  a 
  priori 
  ground, 
  since 
  there 
  is 
  an 
  important 
  unconformity 
  in 
  

   the 
  slate 
  region 
  between 
  the 
  Lower 
  Cambric 
  Georgian 
  rocks 
  and 
  

   the 
  overlying 
  Ordovicic 
  beds, 
  marking 
  a 
  long 
  period 
  of 
  emergence 
  

   and 
  erosion, 
  we 
  should 
  expect 
  the 
  Ordovicic 
  series 
  to 
  begin 
  with 
  

   the 
  coarse 
  grits, 
  these 
  being 
  followed 
  by 
  the 
  fine 
  siliceous 
  muds 
  

   that 
  produced 
  the 
  white 
  beds, 
  and 
  the 
  latter 
  again 
  by 
  the 
  argilla- 
  

   ceous 
  muds 
  that 
  become 
  the 
  dark 
  graptolite 
  shales. 
  This 
  succession 
  

   agrees 
  with 
  the 
  Willard 
  mountain 
  section 
  and 
  appears 
  to 
  us 
  the 
  

   true 
  one. 
  

  

  Another 
  question 
  which 
  can 
  not 
  be 
  satisfactorily 
  answered 
  is 
  

   that 
  of 
  the 
  thickness 
  of 
  the 
  Normanskill 
  formation 
  and 
  of 
  its 
  

   divisions 
  in 
  this 
  region. 
  Dale, 
  in 
  the 
  above-mentioned 
  jtable, 
  

   assigns 
  the 
  " 
  Hudson 
  shales 
  " 
  a 
  thickness 
  of 
  50+ 
  feet 
  ; 
  the 
  " 
  Hud- 
  

   son 
  white 
  beds 
  " 
  400 
  feet 
  or 
  less 
  and 
  to 
  the 
  " 
  Hudson 
  grits 
  " 
  500+ 
  

   feet; 
  and 
  in 
  a 
  later 
  paper 
  (1904, 
  page 
  37) 
  the 
  "Hudson 
  forma- 
  

   tion 
  " 
  of 
  Rensselaer 
  county 
  (including 
  the 
  Snake 
  Hill 
  beds 
  and 
  

   colored 
  shales) 
  is 
  estimated 
  at 
  1200 
  to 
  2500? 
  feet. 
  A 
  former 
  esti- 
  

   mate 
  for 
  the 
  Hudson 
  formation 
  on 
  the 
  east 
  side 
  of 
  the 
  Hudson 
  

   river 
  by 
  Walcott 
  (1890, 
  page 
  346) 
  had 
  been 
  5000 
  feet. 
  This, 
  as 
  

   well 
  as 
  Ashburner's 
  estimate 
  of 
  3500 
  feet 
  for 
  the 
  Altamont 
  well, 
  

   are 
  considered 
  by 
  Dale 
  as 
  too 
  high, 
  who 
  holds 
  that 
  " 
  in 
  a 
  region 
  

   of 
  such 
  moderate 
  relief 
  a 
  mass 
  of 
  beds 
  2500 
  feet 
  thick, 
  1 
  thrown 
  

   into 
  small, 
  close 
  and 
  mostly 
  overturned 
  folds, 
  would 
  account 
  for 
  

   such 
  a 
  rock 
  surface 
  as 
  that 
  depicted 
  in 
  that 
  portion 
  of 
  the 
  map 
  

   which 
  lies 
  west 
  of 
  the 
  Taconic 
  range." 
  While 
  we 
  agree 
  with 
  Dale 
  

   in 
  this 
  latter 
  view, 
  we 
  yet 
  consider 
  his 
  estimates 
  as 
  giving 
  the 
  

   minimal 
  estimates, 
  rather 
  than 
  the 
  maximal 
  ones, 
  for 
  where 
  the 
  

   succession 
  of 
  faunules 
  permitted 
  the 
  exclusion 
  of 
  the 
  repetition 
  of 
  

   beds 
  as 
  a 
  factor 
  in 
  increasing 
  the 
  apparent 
  thickness 
  of 
  the 
  forma- 
  

   tions, 
  considerably 
  greater 
  thicknesses 
  were 
  obtained 
  by 
  the 
  writer. 
  

   In 
  the 
  case 
  of 
  the 
  Deep 
  Kill 
  graptolite' 
  shales 
  of 
  Beekmantown 
  age, 
  

   for 
  instance, 
  the 
  faunal 
  zones 
  indicate 
  a 
  thickness 
  of 
  the 
  formation 
  

   of 
  from 
  200 
  to 
  300 
  feet, 
  while 
  Dale 
  observed 
  not 
  more 
  than 
  50 
  

   feet 
  of 
  this 
  formation 
  in 
  any 
  one 
  place. 
  It 
  is 
  true 
  that 
  Ashburner's 
  

   measurement 
  of 
  3500 
  feet 
  in 
  the 
  Altamont 
  well 
  is 
  not 
  applicable 
  to 
  

   this 
  shale 
  region, 
  because 
  the 
  shales 
  at 
  Altamont 
  belong 
  in 
  another 
  

  

  1 
  Dale's 
  estimate 
  of 
  the 
  combined 
  thickness 
  of 
  the 
  Lower 
  Cambric 
  and 
  

   Lower 
  Siluric 
  in 
  the 
  slate 
  belt. 
  

  

  