﻿358 
  Spencer 
  — 
  Origin 
  and 
  Age 
  of 
  the 
  Ontario 
  Shore-Line. 
  

  

  remainder 
  of 
  the 
  gap 
  closed 
  by 
  crib-work 
  and 
  piling, 
  and 
  the 
  

   deepened 
  canal 
  is 
  now 
  protected 
  by 
  transverse 
  piers 
  nearly 
  half 
  

   a 
  mile 
  long. 
  

  

  The 
  sands 
  and 
  gravels 
  were 
  originally 
  derived 
  from 
  the 
  

   remains 
  of 
  the 
  drifts 
  of 
  Scarboro 
  Bluffs, 
  which 
  upon 
  being 
  

   undermined 
  and 
  wave-washed 
  were 
  current-borne 
  westward. 
  

   However, 
  these 
  features 
  were 
  insufficient 
  to 
  explain 
  the 
  

   origin 
  of 
  Toronto 
  Island 
  until 
  soundings 
  and 
  borings 
  had 
  

   revealed 
  the 
  character 
  of 
  the 
  underlying 
  delta 
  deposits 
  hitherto 
  

   unknown. 
  The 
  source 
  of 
  these 
  is 
  found 
  in 
  the 
  excavation 
  of 
  the 
  

   Don 
  valley* 
  (behind 
  the 
  barrier 
  to 
  Toronto 
  and 
  Ashbridge 
  

   bays 
  (see 
  map) 
  which, 
  below 
  a 
  height 
  of 
  190 
  feet 
  above 
  the 
  

   lake, 
  has 
  been 
  excavated 
  since 
  the 
  Iroquois 
  epoch. 
  The 
  delta 
  

   basement 
  (with 
  the 
  closely 
  packed 
  very 
  fine 
  sand 
  which 
  may 
  

   be 
  inter-Glacial) 
  is 
  more 
  than 
  six 
  times 
  the 
  thickness 
  of 
  the 
  

   Ontario 
  beach 
  itself. 
  

  

  The 
  now 
  buried 
  delta 
  was 
  accumulated 
  while 
  the 
  lake 
  sur- 
  

   face 
  was 
  rising 
  from 
  its 
  lowest 
  level 
  (some 
  200 
  feet) 
  to 
  that 
  of 
  

   Mill-Haven 
  stage, 
  which 
  is 
  now 
  represented 
  by 
  the 
  "bottom" 
  

   of 
  the 
  present 
  valley, 
  before 
  the 
  waters 
  fell 
  again 
  to 
  the 
  exist- 
  

   ing 
  shore, 
  when 
  the 
  beach 
  materials 
  from 
  Scarboro 
  Bluffs 
  were 
  

   brought 
  by 
  the 
  waves 
  to 
  cover 
  the 
  delta 
  mass. 
  

  

  While 
  elsewhere 
  the 
  lake 
  deepens 
  gradually 
  to 
  75-100 
  feet 
  

   or 
  more, 
  the 
  slope 
  of 
  its 
  floor 
  is 
  only 
  17 
  feet 
  in 
  a 
  distance 
  of 
  

   1,600 
  feet 
  at 
  the 
  southwestern 
  angle 
  of 
  the 
  Island, 
  but 
  im- 
  

   mediately 
  beyond 
  it 
  descends 
  abruptly 
  to 
  69 
  feet 
  (in 
  1,400 
  feet) 
  

   and 
  to 
  150 
  feet 
  just 
  beyond 
  (section 
  A, 
  fig. 
  2). 
  Such 
  is 
  in 
  

   strong 
  contrast 
  with 
  the 
  gentle 
  gradient 
  elsewhere. 
  This 
  

   changing 
  slope 
  also 
  shows 
  the 
  approximate 
  limit 
  of 
  wave 
  action 
  

   to 
  20 
  feet 
  as 
  appears 
  farther 
  east. 
  No 
  features 
  below 
  20-30 
  

   feet 
  can 
  be 
  correlated 
  with 
  the 
  Ontario 
  Beach. 
  

  

  The 
  materials 
  of 
  both 
  the 
  older 
  delta 
  and 
  the 
  newer 
  beach 
  

   have 
  been 
  dumped 
  into 
  the 
  eastern 
  side 
  of 
  the 
  Humber 
  Embay- 
  

   ment, 
  producing 
  the 
  peculiar 
  configuration 
  of 
  the 
  southwestern 
  

   extremity 
  of 
  the 
  Island. 
  But 
  the 
  Humber 
  is 
  unlike 
  the 
  Don 
  

   Y 
  alley, 
  the 
  former 
  being 
  of 
  inter-Glacial 
  age, 
  with 
  a 
  later 
  

   mantle 
  but 
  without 
  a 
  post-Iroquois 
  delta 
  as 
  has 
  the 
  Don. 
  

  

  Age 
  of 
  Lake 
  Ontario 
  and 
  of 
  the 
  Saint 
  Laicrence 
  River. 
  

  

  Investigations 
  about 
  Toronto 
  Island 
  alone 
  furnish 
  no 
  clue 
  of 
  

   the 
  age 
  of 
  the 
  Ontario 
  Beach 
  ; 
  but 
  from 
  the 
  encroachments 
  of 
  

   the 
  lake 
  upon 
  Scarboro 
  Bluffs, 
  for 
  over 
  9 
  miles 
  between 
  

   Victoria 
  Park 
  and 
  Port 
  Union, 
  and 
  from 
  the 
  topography 
  of 
  the 
  

  

  * 
  Such 
  materials 
  as 
  were 
  removed 
  may 
  be 
  seen 
  at 
  the 
  Don 
  brick 
  yard 
  ; 
  till 
  

   3 
  feet 
  : 
  stratified 
  sand 
  with 
  grit 
  and 
  layers 
  of 
  clay 
  20-25 
  feet 
  ; 
  laminated 
  

   drab 
  clay 
  (sandy) 
  about 
  25 
  feet 
  ; 
  clay 
  with 
  fine 
  sandy 
  laminations 
  85-40 
  

   feet 
  ; 
  sand 
  coarser 
  6 
  feet 
  ; 
  fine 
  sandy 
  clay 
  40 
  feet 
  covered 
  with 
  sand. 
  

  

  