﻿GEOLOGY 
  OF 
  THE 
  PORT 
  LEYDEN 
  QUADRANGLE 
  7 
  

  

  on, 
  one 
  layer 
  above 
  another, 
  the 
  3^ounger 
  deposits 
  overlapping 
  

   each 
  other 
  and 
  encroaching 
  upon 
  the 
  sinking 
  land 
  surface. 
  

   Since 
  the 
  subsidence 
  was 
  not 
  entirely 
  uniform 
  on 
  all 
  sides 
  

   certain 
  local 
  variations 
  in 
  deposition 
  occurred. 
  

  

  The 
  first 
  of 
  the 
  deposits 
  to 
  form 
  upon 
  the 
  sinking 
  floor 
  was 
  

   the 
  Potsdam 
  (Cambric) 
  sandstone 
  now 
  found 
  exposed 
  nearly 
  

   everywhere 
  except 
  along 
  the 
  southwest 
  border. 
  After 
  this 
  the 
  

   sediments 
  changed 
  in 
  character 
  and 
  the 
  limestones 
  of 
  the 
  Beek- 
  

   mantown 
  (Lower 
  Siluric) 
  were 
  laid 
  down. 
  Then 
  followed 
  the 
  

   deposition 
  of 
  the 
  highly 
  fossiliferous 
  Trenton 
  (Lower 
  Siluric) 
  

   limestones 
  including 
  the 
  Lowville 
  and 
  the 
  Black 
  River 
  lime- 
  

   stones. 
  The 
  fairly 
  clear 
  waters 
  full 
  of 
  animal 
  life 
  then 
  gave 
  way 
  

   to 
  the 
  muddy 
  waters 
  of 
  the 
  Utica, 
  when 
  the 
  Utica 
  shales 
  (Lower 
  

   Siluric) 
  were 
  deposited. 
  At 
  this 
  time 
  the 
  Adirondack 
  region 
  

   was 
  probably 
  all 
  under 
  water. 
  Next 
  came 
  an 
  uplift 
  on 
  the 
  east 
  

   and 
  northeast 
  where 
  depositions 
  ceased. 
  On 
  the 
  south 
  and 
  

   southwest, 
  however, 
  deposition 
  continued 
  and 
  the 
  successive 
  

   formations 
  of 
  the 
  Siluric 
  and 
  Devonic 
  above 
  the 
  Utica 
  shale 
  were 
  

   laid 
  down. 
  These 
  Paleozoic 
  formations 
  may 
  now 
  be 
  seen 
  as 
  

   one 
  passes 
  from 
  the 
  Adirondacks 
  southward 
  to 
  the 
  southern 
  

   border 
  of 
  the 
  State. 
  

  

  The 
  last 
  period 
  of 
  igneous 
  activity 
  in 
  the 
  Adirondacks 
  

   occurred 
  some 
  time 
  after 
  the 
  close 
  of 
  the 
  Lower 
  Siluric. 
  This 
  

   activity 
  was 
  of 
  minor 
  extent 
  and 
  showed 
  itself 
  in 
  the 
  form 
  of 
  

   dikes. 
  

  

  At 
  some 
  time 
  after 
  the 
  deposition 
  of 
  the 
  Utica 
  shale 
  the 
  rocks, 
  

   especially 
  along 
  the 
  southern 
  border, 
  were 
  deformed 
  chiefly 
  by 
  

   faulting. 
  A 
  series 
  of 
  these 
  faults 
  extends 
  across 
  the 
  Mohawk 
  

   valley. 
  The 
  western 
  Adirondacks, 
  including 
  the 
  Port 
  Leyden 
  

   quadrangle, 
  have 
  been 
  subjected 
  to 
  erosion 
  for 
  a 
  vast 
  length 
  of 
  

   time, 
  certainly 
  since 
  the 
  close 
  of 
  the 
  Paleozoic 
  and 
  more 
  than 
  

   likely 
  since 
  the 
  Devonic. 
  During 
  this 
  great 
  lapse 
  of 
  time 
  a 
  large 
  

   amount 
  of 
  material 
  has 
  been 
  removed. 
  Doubtless 
  the 
  whole 
  

   Port 
  Leyden 
  quadrangle 
  was 
  at 
  one 
  time 
  covered 
  by 
  the 
  Utica 
  

   and 
  Lorraine 
  shales, 
  which 
  have 
  all 
  been 
  removed 
  except 
  along 
  

   the 
  western 
  side. 
  

  

  The 
  superficial 
  deposits, 
  such 
  as 
  the 
  sands 
  and 
  gravels 
  which 
  

   are 
  so 
  prominent 
  in 
  the 
  Port 
  Leyden 
  district, 
  were 
  formed 
  by, 
  

   or 
  along 
  the 
  border 
  of, 
  the 
  great 
  ice 
  sheet 
  of 
  the 
  Glacial 
  age. 
  

   From 
  the 
  geological 
  standpoint 
  this 
  ice 
  sheet 
  was 
  present 
  only 
  

   quite 
  recently 
  and 
  covered 
  most 
  of 
  New 
  York 
  State. 
  

  

  