﻿Report 
  of 
  the 
  State 
  Geologist. 
  399 
  

  

  the 
  thickness 
  decreases 
  very 
  gradually. 
  The 
  members 
  constitut- 
  

   ing 
  the 
  formation 
  in 
  its 
  typical 
  development, 
  beginning 
  at 
  the 
  

   top, 
  are 
  a 
  pure 
  semi-crystalline, 
  massive, 
  very 
  fossiliferous 
  lime- 
  

   stone, 
  a 
  thick 
  series 
  of 
  shaly 
  limestone, 
  and 
  the 
  basal 
  series, 
  thin- 
  

   bedded 
  dark 
  limestones 
  of 
  the 
  Tentaculite 
  beds. 
  On 
  Catskill 
  

   creek 
  a 
  higher 
  member 
  of 
  impure 
  shaly 
  limestone 
  comes 
  in 
  above 
  

   the 
  pure, 
  massive 
  beds, 
  thickens 
  rapidly, 
  and 
  continues 
  southward 
  

   to 
  and 
  through 
  New 
  Jersey, 
  The 
  Iielderberg 
  formation 
  pre- 
  

   serves 
  its 
  typical 
  characters 
  with 
  some 
  local 
  variations 
  in 
  thick- 
  

   ness, 
  to 
  a 
  few 
  miles 
  west 
  of 
  Cherry 
  Valley. 
  Then 
  the 
  upper 
  

   limestone 
  beds 
  thin 
  out, 
  and 
  on 
  the 
  road 
  from 
  West 
  Winfield 
  to 
  

   Litchfield 
  in 
  the 
  southwestern 
  corner 
  of 
  Herkimer 
  county, 
  the 
  

   Pentamerus 
  beds 
  lie 
  directly 
  under 
  the 
  Onondaga 
  limestone. 
  

   This, 
  however, 
  as 
  I 
  shall 
  show 
  beyond, 
  is 
  a 
  region 
  of 
  uplift 
  and 
  

   erosion 
  in 
  pre-Onondaga 
  times, 
  which 
  has 
  removed 
  the 
  Oriskany 
  

   sandstone 
  and 
  upper 
  members 
  of 
  the 
  Helderberg 
  limestones 
  

   which 
  come 
  in 
  again 
  westward, 
  and 
  are 
  finely 
  exposed 
  at 
  Oris- 
  

   kany 
  Falls. 
  S. 
  G-. 
  Williams* 
  has 
  described 
  and 
  discussed 
  in 
  

   detail 
  the 
  relations 
  at 
  this 
  locality, 
  and 
  I 
  shall 
  only 
  briefly 
  men- 
  

   tion 
  them. 
  Here 
  120 
  feet 
  of 
  beds 
  are 
  exposed 
  in 
  and 
  about 
  the 
  

   quarries, 
  of 
  which 
  fifty 
  feet 
  are 
  quite 
  distinctively 
  of 
  the 
  Tenta- 
  

   culite 
  beds, 
  forty 
  feet 
  of 
  gray 
  beds 
  in 
  greater 
  part 
  of 
  Penta- 
  

   merus 
  limestone 
  age, 
  but 
  merging 
  into 
  the 
  character 
  of 
  the 
  lower 
  

   beds, 
  a 
  few 
  feet 
  of 
  beds 
  with 
  mixed 
  Pentamerus 
  and 
  shaly 
  lime- 
  

   stone 
  fauna, 
  and, 
  at 
  the 
  top, 
  twenty-five 
  feet 
  of 
  gray 
  subcrystal- 
  

   line 
  rock 
  containing 
  a 
  shaly 
  limestone 
  fauna. 
  Twenty-five 
  miles 
  

   west 
  of 
  Perryville, 
  Madison 
  county, 
  L 
  found 
  that 
  this 
  condition 
  

   had 
  continued, 
  the 
  lower 
  members 
  expanding 
  apparently 
  at 
  the 
  

   expense 
  of 
  the 
  Pentamerus 
  beds, 
  and 
  the 
  upper 
  members 
  giving 
  

   place 
  to 
  Pentamerus 
  beds. 
  At 
  this 
  locality 
  the 
  Onondaga 
  lime- 
  

   stone 
  was 
  seen 
  lying 
  on 
  a 
  few 
  feet 
  of 
  dark 
  gray 
  limestones 
  con- 
  

   taining 
  Pentamerus^ 
  with 
  a 
  thin 
  local 
  intervening 
  layer 
  of 
  Oris- 
  

   kany 
  at 
  one 
  point, 
  which 
  gave 
  place 
  to 
  a 
  great 
  mass 
  of 
  thin- 
  

   bedded 
  gray 
  limestone 
  below. 
  S. 
  G. 
  Williamsf 
  has 
  called 
  atten- 
  

  

  * 
  The 
  westward 
  extension 
  of 
  rocks 
  of 
  the 
  Lower 
  Helderberg 
  age 
  in 
  New 
  York. 
  im. 
  Jour. 
  

   Scl., 
  3d 
  series, 
  vol. 
  31, 
  pp. 
  139-145; 
  Abstract 
  Am. 
  Assoc. 
  Adv. 
  Sci., 
  Proc 
  , 
  vol. 
  34, 
  pp. 
  235, 
  236; 
  

   Am. 
  Nat., 
  vol. 
  20, 
  p. 
  373. 
  1886. 
  

  

  + 
  Ibid., 
  and 
  Note 
  on 
  the 
  Lower 
  Helderberg 
  rocks 
  of 
  Cayuga 
  lake, 
  New 
  York. 
  6th 
  Report 
  of 
  

   State 
  Geologist, 
  1886, 
  pp. 
  10-12; 
  Abstract 
  Am. 
  Assoc. 
  Adv. 
  Sci., 
  vol. 
  35, 
  pp. 
  214, 
  215. 
  1887. 
  

  

  