﻿GEOLOGY 
  OF 
  SARATOGA 
  SPRINGS 
  AND 
  VICINITY 
  45 
  

  

  Cryptozoon 
  isC. 
  proliferum, 
  but 
  in 
  the 
  upper 
  beds 
  another 
  

   and 
  quite 
  different 
  species 
  comes 
  in. 
  A 
  bed 
  of 
  dove 
  limestone 
  which 
  

   occurs 
  capping 
  the 
  upper, 
  light 
  colored 
  dolomite 
  to 
  the 
  west 
  of 
  

   Saratoga, 
  exposes 
  this 
  Cryptozoon 
  most 
  excellently 
  (plates 
  9 
  and 
  

   10). 
  The 
  same 
  species 
  occurs 
  at 
  the 
  summit 
  of 
  the 
  formation 
  at 
  

   Ticonderoga 
  and 
  elsewhere. 
  The 
  summit 
  beds 
  are 
  usually 
  full 
  of 
  

   chert 
  and 
  the 
  Cryptozoon 
  is 
  often 
  heavily 
  silicified. 
  

  

  Unconformity 
  at 
  the 
  summit 
  of 
  the 
  Little 
  Falls. 
  The 
  Little 
  

   Falls 
  dolomite 
  is 
  directly 
  overlaid, 
  in 
  the 
  Saratoga 
  region, 
  by 
  the 
  

   Amsterdam 
  limestone 
  of 
  upper 
  Black 
  River 
  age. 
  No 
  representa- 
  

   tives 
  of 
  the 
  Beekmantown 
  and 
  Chazy 
  groups 
  appear 
  in 
  the 
  section, 
  

   and 
  the 
  lower 
  beds 
  of 
  the 
  Black 
  River 
  group 
  are 
  also 
  lacking. 
  The 
  

   Tribes 
  Hill 
  limestone, 
  which 
  overlies 
  the 
  Little 
  Falls 
  in 
  the 
  Mo- 
  

   hawk 
  valley 
  and 
  is 
  of 
  probable 
  lowest 
  Beekmantown 
  age, 
  is 
  absent 
  

   about 
  Saratoga. 
  It 
  may 
  have 
  been 
  thinly 
  deposited 
  and 
  subse- 
  

   quently 
  eroded. 
  It 
  seems 
  quite 
  safe 
  to 
  say 
  that 
  the 
  Beekmantown 
  

   and 
  Chazy 
  deposits 
  never 
  reached 
  the 
  district, 
  and 
  that 
  the 
  lower 
  

   Black 
  River 
  rocks 
  were 
  laid 
  down 
  but 
  thinly 
  if 
  at 
  all. 
  

  

  Aside 
  from 
  the 
  absence 
  of 
  these 
  rocks 
  from 
  the 
  region, 
  the 
  physi- 
  

   cal 
  evidence 
  of 
  the 
  unconformity 
  is 
  twofold. 
  The 
  base 
  of 
  the 
  Am- 
  

   sterdam 
  rests 
  on 
  quite 
  different 
  beds 
  of 
  the 
  Little 
  Falls, 
  at 
  the 
  vari- 
  

   ous 
  exposures 
  of 
  the 
  contact, 
  indicating 
  erosion 
  of 
  the 
  surface 
  prior 
  

   to 
  Amsterdam 
  deposit; 
  and 
  the 
  basal 
  bed 
  of 
  the 
  Amsterdam 
  varies 
  

   from 
  place 
  to 
  place, 
  showing 
  that 
  the 
  surface 
  upon 
  which 
  it 
  was 
  

   laid 
  down 
  was 
  irregular 
  and 
  that 
  the 
  lower 
  beds 
  of 
  the 
  Amsterdam 
  

   are 
  only 
  found 
  in 
  the 
  old 
  depressions. 
  Furthermore 
  the 
  Amster- 
  

   dam 
  begins 
  with 
  a 
  basal 
  conglomerate 
  full 
  of 
  Little 
  Falls 
  pebbles. 
  

   This 
  basal 
  layer 
  is 
  best 
  seen 
  at 
  Saratoga. 
  In 
  the 
  northern 
  part 
  

   of 
  the 
  village, 
  just 
  west 
  of 
  the 
  fault 
  line 
  and 
  just 
  north 
  of 
  where 
  the 
  

   Delaware 
  & 
  Hudson 
  Railroad 
  crosses 
  the 
  fault, 
  thin 
  patches 
  of 
  

   this 
  conglomerate 
  may 
  be 
  seen 
  resting 
  on 
  the 
  upper 
  surface 
  of 
  the 
  

   Little 
  Falls, 
  proving 
  that 
  it 
  is 
  the 
  very 
  top 
  of 
  that 
  formation 
  which 
  

   there 
  forms 
  the 
  upthrow 
  face 
  of 
  the 
  fault. 
  

  

  AMSTERDAM 
  LIMESTONE 
  

  

  In 
  the 
  sections 
  of 
  the 
  eastern 
  Mohawk 
  region 
  there 
  appears, 
  

   beneath 
  the 
  rocks 
  which 
  are 
  strictly 
  referable 
  to 
  the 
  Trenton 
  group, 
  

   a 
  thin 
  limestone 
  formation 
  which 
  is 
  wholly 
  distinct 
  from 
  anything 
  

   found 
  in 
  the 
  vicinity 
  of 
  Trenton 
  Falls 
  and 
  which 
  we 
  regard 
  as 
  an 
  

   upper 
  member 
  of 
  the 
  Black 
  River 
  group 
  and 
  are 
  calling 
  the 
  Amster- 
  

   dam 
  limestone. 
  A 
  detailed 
  account 
  of 
  the 
  formation 
  in 
  the 
  type 
  

  

  