﻿GEOLOGY 
  OF 
  THE 
  PORT 
  LEYDEN 
  QUADRANGLE 
  53 
  

  

  thin 
  and 
  after 
  the 
  formation 
  of 
  the 
  kames 
  and 
  withdrawal 
  of 
  the 
  

   ice 
  edge, 
  the 
  delta 
  sands 
  were 
  deposited 
  around 
  them 
  but 
  not 
  with 
  

   sufficient 
  depth 
  to 
  cover 
  them. 
  

  

  Erratics 
  

  

  Like 
  the 
  kames, 
  glacial 
  boulders 
  or 
  erratics 
  are 
  scattered 
  over 
  all 
  

   parts 
  of 
  the 
  quadrangle 
  except 
  the 
  typical 
  sand 
  plains. 
  Their 
  

   absence 
  from 
  the 
  sand 
  plain 
  belt 
  is 
  to 
  be 
  explained 
  in 
  much 
  the 
  

   same 
  way 
  as 
  the 
  absence 
  of 
  the 
  kames, 
  that 
  is 
  after 
  the 
  boulders 
  

   were 
  dropped 
  by 
  the 
  melting 
  ice 
  they 
  were 
  covered 
  by 
  the 
  delta 
  

   deposits 
  so 
  that 
  they 
  are 
  scarcely 
  ever 
  seen 
  except 
  along 
  the 
  larger 
  

   stream 
  courses 
  where 
  they 
  have 
  again 
  been 
  exposed 
  by 
  erosion. 
  A 
  

   good 
  many 
  are 
  present 
  along 
  the 
  western 
  front 
  of 
  the 
  delta 
  terrace 
  

   particularly 
  in 
  the 
  vicinity 
  of 
  Greig. 
  They 
  are 
  also 
  strewn 
  over 
  

   the 
  Paleozoic 
  rock 
  area, 
  even 
  on 
  the 
  high 
  land 
  of 
  Tug 
  and 
  Mohawk 
  

   hills. 
  

  

  The 
  erratics 
  are 
  mostly 
  from 
  the 
  hard, 
  resistant 
  Precambric 
  

   formations 
  and, 
  as 
  above 
  pointed 
  out, 
  their 
  presence 
  on 
  the 
  high 
  

   western 
  portion 
  of 
  the 
  quadrangle 
  strongly 
  argues 
  for 
  a 
  southerly 
  

   or 
  southwesterly 
  ice 
  current 
  at 
  one 
  time. 
  The 
  largest 
  erratic 
  ob- 
  

   served 
  by 
  the 
  writer 
  is 
  one 
  of 
  quartzose 
  syenite, 
  already 
  referred 
  

   to, 
  which 
  rests 
  upon 
  the 
  Black 
  River 
  limestone 
  about 
  2 
  miles 
  north- 
  

   east 
  of 
  Boonville. 
  This 
  boulder 
  measures 
  about 
  2^] 
  feet 
  across 
  and 
  

   17 
  feet 
  high. 
  Another 
  large 
  one 
  may 
  be 
  seen 
  in 
  the 
  field 
  about 
  ^ 
  

   of 
  a 
  mile 
  east-northeast 
  of 
  Denley 
  station. 
  

  

  Glacial 
  lakes 
  

  

  A 
  very 
  interesting 
  and 
  extensive 
  glacial 
  lake 
  occupied 
  all 
  of 
  the 
  

   sand-flat 
  country 
  on 
  the 
  east 
  side 
  of 
  Black 
  river 
  between 
  Forest- 
  

   •port 
  and 
  Lowville. 
  It 
  also 
  extended 
  somewhat 
  west 
  of 
  Black 
  river 
  

   in 
  the 
  vicinity 
  of 
  Boonville, 
  and 
  to 
  an 
  unknown 
  distance 
  north 
  of 
  

   Lowville. 
  The 
  former 
  presence 
  of 
  this 
  large 
  lake 
  is 
  conclusively 
  

   shown 
  by 
  the 
  great 
  development 
  of 
  unquestioned 
  delta 
  deposits, 
  

   associated 
  with 
  clays, 
  and 
  the 
  remarkably 
  concordant 
  altitudes 
  of 
  

   the 
  sand 
  plains 
  \see 
  above]. 
  These 
  waters 
  were 
  impounded 
  by 
  the 
  

   waning 
  lobe 
  of 
  ice 
  in 
  the 
  Black 
  river 
  valley. 
  The 
  kames 
  and 
  drift 
  

   boulders 
  along 
  the 
  western 
  edge 
  of 
  the 
  great 
  delta 
  de>posit 
  show 
  an 
  

   ice 
  contact 
  from 
  there 
  ; 
  also 
  the 
  absence 
  of 
  delta 
  deposits 
  on 
  the 
  

   west 
  side 
  of 
  the 
  valley, 
  under 
  Tug 
  hill, 
  shows 
  that 
  the 
  lake 
  did 
  not 
  

   extend 
  that 
  far 
  west. 
  Again 
  the 
  failure 
  of 
  any 
  delta 
  deposits 
  to 
  

   reach 
  out 
  to 
  or 
  across 
  the 
  valley 
  bottom 
  also 
  argues 
  for 
  ice 
  occu- 
  

  

  