﻿GEOLOGY 
  OF 
  THE 
  PORT 
  LEYDEX 
  QUADRANGLE 
  55 
  

  

  stream 
  is 
  developing 
  terraces 
  through 
  the 
  old 
  lake 
  deposits 
  of 
  tho 
  

   valley 
  bottom. 
  

  

  Drainage 
  

  

  Black 
  river 
  and 
  its 
  tributaries. 
  From 
  Hawkinsville 
  to 
  opposite 
  

   Denley, 
  Black 
  river 
  is 
  certainly 
  out 
  of 
  its 
  preglacial 
  channel 
  as 
  

   shown 
  by 
  the 
  gorge 
  cut 
  into 
  the 
  limestones. 
  Its 
  former 
  course 
  was 
  

   probably 
  about 
  2 
  miles 
  eastward 
  along 
  the 
  Paleozoic-Precambric 
  

   boundary. 
  Between 
  Denley 
  and 
  Port 
  Leyden 
  it 
  is 
  practically 
  in 
  its 
  

   old 
  channel. 
  Thence 
  to 
  east 
  of 
  Lowville 
  the 
  stream 
  is 
  somewhat 
  

   west 
  of 
  the 
  preglacial 
  course 
  due 
  to 
  the 
  westward 
  shifting 
  of 
  the 
  

   Faleozoic-Precambric 
  boundary 
  by 
  erosion 
  during 
  glacial 
  times. 
  It 
  

   is 
  "doubtful 
  if 
  any 
  of 
  the 
  tributaries 
  of 
  Black 
  river, 
  which 
  cut 
  

   through 
  the 
  delta 
  deposits 
  and 
  into 
  the 
  Precambrics, 
  follow 
  their 
  

   old 
  channels 
  because 
  they 
  have 
  be.en 
  superimposed 
  upon 
  the 
  Pre- 
  

   cambric 
  surface. 
  Thus 
  Aloose 
  river 
  has 
  cut 
  through 
  the 
  deep 
  sands 
  

   and 
  is 
  now 
  engaged 
  in 
  eroding 
  a 
  channel, 
  with 
  gorges 
  and 
  water- 
  

   falls, 
  into 
  the 
  Precambrics. 
  

  

  Origin 
  of 
  the 
  " 
  gulfs." 
  The 
  deep 
  gorges 
  which 
  have 
  been 
  cut 
  

   through 
  the 
  steep 
  eastern 
  front 
  of 
  Tug 
  hill, 
  by 
  tributaries 
  of 
  Black 
  

   river, 
  are 
  locally 
  known 
  as 
  " 
  gulfs." 
  The 
  chief 
  gorges 
  are 
  occu- 
  

   pied 
  by 
  J\Iill, 
  House, 
  Whetstone 
  and 
  Atwater 
  creeks 
  and 
  Roaring 
  

   brook. 
  Whetstone 
  gulf 
  which 
  is 
  perhaps 
  the 
  most 
  interesting, 
  is 
  

   about 
  2 
  miles 
  long 
  and 
  shows 
  a 
  depth 
  of 
  300 
  feet 
  [see 
  pi. 
  9]. 
  Its 
  

   walls 
  are 
  very 
  steep 
  sided 
  to 
  almost 
  vertical, 
  especially 
  in 
  the 
  upper 
  

   end 
  (narrows) 
  where 
  there 
  is 
  just 
  room 
  enough 
  for 
  the 
  stream 
  at 
  

   the 
  bottom 
  and 
  where 
  erosion 
  is 
  now 
  proceeding 
  most 
  rapidly. 
  A 
  

   section 
  showing 
  something 
  like 
  700 
  feet 
  of 
  Lorraine 
  and 
  Utica 
  

   shales 
  is 
  finely 
  exposed 
  in 
  this 
  gorge. 
  The 
  stream 
  emerges 
  from 
  

   the 
  " 
  gulf 
  " 
  upon 
  the 
  broad 
  Hmestone 
  terrace. 
  

  

  During 
  glacial 
  times 
  the 
  shales 
  were 
  eroded 
  back 
  over 
  the 
  lime- 
  

   stone 
  for 
  a 
  considerable 
  distance, 
  and 
  this 
  caused 
  the 
  development 
  

   of 
  the 
  steep 
  eastern 
  front 
  of 
  Tug 
  hill. 
  After 
  the 
  disappearance 
  of 
  

   the 
  ice 
  from 
  the 
  region, 
  all 
  of 
  the 
  east 
  bound 
  streams 
  from 
  Tug 
  

   hill 
  rushed 
  over 
  this 
  steep 
  slope 
  and 
  began 
  to 
  erode 
  notches 
  into 
  its 
  

   summit. 
  These 
  notches 
  were 
  rapidly 
  deepened 
  in 
  the 
  soft 
  shales 
  

   to 
  develop 
  the 
  "gulfs," 
  whose 
  heads 
  have 
  since 
  been 
  cut 
  back 
  to 
  

   their 
  present 
  positions. 
  South 
  of 
  Tug 
  hill 
  the 
  " 
  gulfs 
  " 
  are 
  not 
  so 
  

   well 
  developed 
  because 
  the 
  shales, 
  with 
  their 
  preglacial 
  channels, 
  

   were 
  not 
  cut 
  back 
  by 
  erosion 
  to 
  such 
  a 
  great 
  extent. 
  

  

  