﻿GEOLOGY 
  OF 
  THE 
  PORT 
  LEYDEN 
  QUADRANGLE 
  37 
  

  

  Falls 
  it 
  is 
  as 
  low 
  as 
  20 
  or 
  25 
  degrees. 
  From 
  south 
  of 
  Denley 
  to 
  

   3 
  miles 
  north 
  of 
  Lyons 
  Falls 
  the 
  dip 
  is 
  northward; 
  thence 
  north- 
  

   ward 
  to 
  just 
  south 
  of 
  Glenfield 
  it 
  is 
  southward; 
  thence 
  northward 
  

   to 
  the 
  map 
  limit 
  it 
  is 
  northward. 
  Thus 
  we 
  have 
  good 
  evidence 
  of 
  

   distinct 
  folding 
  of 
  the 
  Precambric 
  rocks 
  on 
  a 
  large 
  scale. 
  Certain 
  

   other 
  Precambric 
  rock 
  structures 
  will 
  be 
  discussed 
  later. 
  

  

  Structure 
  sections 
  

  

  The 
  structure 
  sections 
  shown 
  in 
  figures 
  2-4, 
  page 
  38, 
  have 
  been 
  

   carefully 
  chosen 
  with 
  the 
  idea 
  of 
  giving 
  the 
  best 
  general 
  notion 
  of 
  

   the 
  various 
  rock 
  formations 
  and 
  their 
  relationships 
  to 
  each 
  other. 
  

  

  PALEOZOIC 
  OVERLAP 
  

  

  It 
  is 
  well 
  known 
  that 
  during 
  the 
  general 
  subsidence 
  (barring 
  cer- 
  

   tain 
  minor 
  oscillations 
  of 
  level) 
  of 
  the 
  Adirondack 
  region 
  in 
  early 
  

   Paleozoic 
  times, 
  sediments 
  were 
  being 
  deposited 
  on 
  the 
  Precambric 
  

   surface 
  and 
  that 
  these 
  sediments 
  gradually 
  encroached 
  upon 
  the 
  

   sinking 
  land 
  mass 
  until 
  nearly 
  all, 
  if 
  not 
  all, 
  of 
  the 
  Adirondack 
  

   region 
  was 
  covered 
  by 
  them. 
  The 
  younger 
  formations 
  extended 
  

   farther 
  in 
  than 
  the 
  older 
  ones 
  upon 
  the 
  sinking 
  surface, 
  thus 
  con- 
  

   stituting 
  an 
  overlap 
  of 
  the 
  Paleozoic 
  sediments 
  upon 
  the 
  Precambric 
  

   crystallines. 
  The 
  stripping 
  off 
  of 
  this 
  Paleozoic 
  cover 
  has 
  been 
  

   going 
  on 
  since 
  the 
  close 
  of 
  the 
  Paleozoic 
  era, 
  at 
  least, 
  and 
  the 
  

   exposed 
  surface 
  of 
  the 
  Precambric 
  rocks 
  is 
  still 
  being 
  enlarged 
  by 
  

   this 
  same 
  process. 
  A 
  glance 
  at 
  the 
  structure 
  sections 
  [fig. 
  2-4] 
  

   will 
  show 
  the 
  eroded 
  edges 
  of 
  about 
  1500 
  feet 
  of 
  sediments 
  which 
  

   formerly 
  must 
  have 
  extended 
  farther 
  eastward 
  upon 
  the 
  Pre- 
  

   cambric 
  surface. 
  In 
  the 
  Port 
  Leyden 
  district 
  we 
  have 
  positive 
  evi- 
  

   dence 
  to 
  prove 
  the 
  Paleozoic 
  overlap. 
  

  

  On 
  the 
  western 
  side 
  of 
  the 
  Adirondacks 
  the 
  oldest 
  overlapping 
  

   formation 
  is 
  the 
  Potsdam 
  sandstone. 
  It 
  is 
  not 
  present 
  in 
  outcrop 
  

   within 
  the 
  Port 
  Leyden 
  quadrangle, 
  the 
  nearest 
  exposures 
  being 
  

   about 
  20 
  miles 
  northward 
  in 
  the 
  vicinity 
  of 
  Carthage. 
  Accord- 
  

   ing 
  to 
  Orton 
  ^ 
  the 
  Potsdam, 
  resting 
  upon 
  the 
  Precambrics, 
  occurs 
  

   in 
  Oswego 
  county 
  to 
  the 
  west 
  and 
  southwest 
  of 
  Port 
  Leyden 
  as 
  

   shown 
  in 
  deep 
  well 
  sections. 
  Thus 
  the 
  deep 
  well 
  at 
  Central 
  Square 
  

   shows 
  156 
  feet 
  of 
  sandstone; 
  the 
  well 
  at 
  Parish 
  50 
  feet 
  of 
  sand- 
  

   stone 
  and 
  the 
  well 
  at 
  Stillwater 
  (southeast 
  of 
  Orwell) 
  at 
  least 
  49 
  

  

  ' 
  N. 
  Y. 
  State 
  Mus. 
  Bui. 
  30. 
  

  

  