﻿GEOLOGY 
  OF 
  SARATOGA 
  SPRINGS 
  AND 
  VICINITY 
  47 
  

  

  Since 
  the 
  actual 
  summit 
  nowhere 
  shows, 
  we 
  are 
  somewhat 
  in 
  

   doubt 
  as 
  to 
  the 
  actual 
  thickness 
  of 
  the 
  formation 
  and 
  as 
  to 
  what 
  

   directly 
  overlies. 
  The 
  many 
  drilled 
  wells 
  to 
  the 
  south 
  of 
  Saratoga 
  

   aid 
  in 
  supplying 
  the 
  information. 
  Underneath 
  the 
  Canajoharie 
  shale 
  

   these 
  wells 
  show 
  an 
  average 
  thickness 
  of 
  from 
  40 
  to 
  45 
  feet 
  of 
  

   alternating 
  shale 
  and 
  limestone, 
  beneath 
  which 
  comes 
  35 
  to 
  40 
  feet 
  

   of 
  limestone 
  and 
  then 
  the 
  Little 
  Falls. 
  The 
  limestone 
  is 
  Amster- 
  

   dam. 
  Whether 
  any 
  of 
  the 
  alternating 
  shale 
  and 
  limestone 
  is 
  also 
  

   to 
  be 
  classed 
  as 
  Amsterdam 
  we 
  do 
  not 
  know. 
  We 
  have 
  seen 
  but 
  

   one 
  exposure 
  of 
  the 
  horizon, 
  in 
  a 
  cut 
  by 
  the 
  roadside 
  a 
  mile 
  east 
  

   of 
  Rock 
  City 
  Falls, 
  an 
  exposure 
  so 
  poor 
  as 
  really 
  not 
  to 
  merit 
  the 
  

   name. 
  The 
  fauna 
  was 
  Trenton, 
  not 
  Amsterdam; 
  but 
  the 
  exposure 
  

   may 
  not 
  have 
  been 
  basal. 
  We 
  incline 
  to 
  the 
  opinion 
  that 
  this 
  al- 
  

   ternating 
  shale 
  and 
  limestone 
  is 
  all 
  Trenton, 
  and 
  that 
  the 
  thickness 
  

   of 
  the 
  Amsterdam 
  is 
  from 
  40 
  to 
  60 
  feet, 
  varying 
  with 
  the 
  irregu- 
  

   larity 
  of 
  the 
  floor 
  on 
  which 
  it 
  was 
  deposited. 
  

  

  The 
  appended 
  list 
  of 
  the 
  more 
  common 
  fossils 
  of 
  the 
  Amsterdam 
  

   we 
  owe 
  to 
  the 
  courtesy 
  of 
  Dr 
  E. 
  O. 
  Ulrich: 
  

  

  Solenopora 
  compacta 
  Columnaria 
  halli 
  

  

  Stictoporella 
  cribrosa 
  Strophomena 
  trentonensis 
  

  

  Rhinidictya 
  mutabilis 
  Dalmanella 
  rogata 
  

  

  Phyllodictya 
  varia 
  Dinorthis 
  pectinella 
  

  

  Eridotrypa 
  minor 
  Bathyurus 
  spiniger 
  

  

  Arthroclema 
  pulchellum 
  ? 
  Leperditia 
  n. 
  sp. 
  

   Pachydictya 
  acuta 
  var. 
  

  

  GLENS 
  FALLS 
  ( 
  BASAL 
  TRENTON 
  ) 
  LIMESTONE 
  

  

  The 
  zone 
  of 
  alternating 
  shale 
  and 
  limestone, 
  some 
  40 
  feet 
  thick, 
  

   which 
  overlies 
  the 
  Amsterdam 
  in 
  the 
  well 
  sections 
  and 
  which 
  is 
  

   not 
  exposed 
  at 
  the 
  surface, 
  is 
  the 
  only 
  zone 
  in 
  the 
  district 
  to 
  which 
  

   the 
  term 
  Trenton 
  limestone 
  could 
  at 
  all 
  properly 
  be 
  applied, 
  and 
  

   there 
  is 
  even 
  question 
  as 
  to 
  its 
  propriety 
  here 
  since 
  the 
  shale 
  exceeds 
  

   the 
  limestone. 
  Outcrops 
  on 
  the 
  Broadalbin 
  quadrangle 
  and 
  in 
  the 
  

   eastern 
  Mohawk 
  valley, 
  where 
  the 
  sections 
  are 
  exceedingly 
  like 
  

   those 
  about 
  Saratoga, 
  leave 
  little 
  doubt 
  that 
  this 
  zone 
  is 
  of 
  lower 
  

   Trenton 
  age. 
  On 
  the 
  Broadalbin 
  quadrangle 
  Miller 
  has 
  mapped 
  

   this 
  zone 
  with 
  the 
  Amsterdam, 
  and 
  separate 
  from 
  the 
  overlying 
  

   Canajoharie 
  shale. 
  The 
  Canajoharie 
  shale, 
  however, 
  is 
  of 
  Tren- 
  

   ton 
  age, 
  and 
  it 
  seems 
  to 
  us 
  more 
  fitting 
  to 
  group 
  the 
  basal 
  zone 
  

   which 
  contains 
  the 
  thin 
  limestone 
  bands 
  with 
  this, 
  as 
  its 
  basal 
  por- 
  

   tion, 
  rather 
  than 
  with 
  the 
  Amsterdam, 
  which 
  we 
  regard 
  as 
  of 
  Black 
  

  

  