﻿rl40 
  NEW 
  YOKK 
  STATE 
  MUSEUM 
  

  

  Fig. 
  3 
  shows 
  the 
  general 
  features 
  of 
  the 
  region. 
  It 
  is 
  not 
  drawn 
  

   to 
  scale, 
  but 
  shows 
  the 
  relation, 
  form 
  and 
  position 
  of 
  the 
  main 
  

   vallej 
  and 
  Six 
  Mile 
  creek 
  valley 
  at 
  the 
  south; 
  the 
  form 
  of 
  the 
  

   lake, 
  the 
  rock 
  hills 
  retreating 
  at 
  the 
  north 
  end 
  and 
  the 
  marsh 
  lined 
  

   with 
  drumlins. 
  

  

  The 
  rock 
  of 
  this 
  region 
  is 
  Devonian, 
  that 
  on 
  top 
  of 
  the 
  high 
  

   hills 
  south 
  of 
  the 
  lake 
  belonging 
  to 
  the 
  Chemung 
  group, 
  while 
  that 
  

   northward 
  belongs 
  to 
  various 
  divisions 
  of 
  the 
  Hamilton. 
  

  

  The 
  general 
  trend 
  of 
  the 
  strata 
  is 
  to 
  rise 
  northward 
  at 
  an 
  angle 
  of 
  

   about 
  two 
  degrees, 
  thus 
  exposing 
  along 
  the 
  lake 
  the 
  Ithaca 
  shale, 
  

   Genesee 
  shale, 
  Tully 
  limestone, 
  Hamilton 
  shale 
  (sub-division), 
  Mar- 
  

   cellus 
  shale, 
  Helderberg 
  limestone, 
  and 
  the 
  Salina 
  group 
  underlying 
  

   the 
  northern 
  end. 
  

  

  Tracing 
  the 
  Tully 
  limestone 
  along 
  the 
  lake 
  it 
  is 
  noticed 
  that 
  it 
  

   rises 
  above 
  the 
  lake 
  level 
  three 
  miles 
  from 
  the 
  southern 
  end. 
  It 
  

   forms 
  an 
  anticline 
  six 
  miles 
  long, 
  reaching 
  the 
  lake 
  surface 
  again 
  

   just 
  below 
  Taughannock, 
  and 
  having 
  a 
  maximum 
  height 
  of 
  150 
  

   feet. 
  Then 
  it 
  follows 
  the 
  shore 
  for 
  several 
  miles 
  and 
  gradually 
  

   recedes 
  from 
  the 
  lake 
  in 
  the 
  form 
  of 
  a 
  terrace, 
  and 
  disappears 
  

   beneath 
  the 
  drift. 
  

  

  • 
  Jointing 
  is 
  well 
  illustrated 
  in 
  all 
  the 
  rocks, 
  and 
  fossils 
  are 
  common 
  

   in 
  many 
  of 
  the 
  strata. 
  In 
  the 
  Marcellus 
  shale 
  are 
  numerous 
  con- 
  

   cretions. 
  The 
  smaller 
  of 
  these 
  are 
  usually 
  centered 
  about 
  nodules 
  

   of 
  iron 
  py 
  rite, 
  and 
  the 
  larger 
  ones 
  — 
  many 
  of 
  which 
  exceed 
  two 
  

   feet 
  in 
  diameter 
  — 
  have 
  cracked 
  and 
  the 
  crevices 
  are 
  filled 
  with 
  

   calcite. 
  

  

  Where 
  the 
  shale 
  forms 
  the 
  shore 
  line, 
  the 
  wave-formed 
  terrace 
  

   is 
  admirably 
  developed, 
  the 
  soft 
  rock 
  weathering 
  so 
  rapidly 
  that 
  

   the 
  wall 
  remains 
  perpendicular. 
  But 
  wave 
  action 
  on 
  this 
  narrow 
  

   lake 
  is 
  incompetent 
  to 
  accoimt 
  entirely 
  for 
  the 
  high 
  rock 
  bluffs 
  

   which 
  may 
  exist. 
  The 
  prevailing 
  winds 
  are 
  a 
  little 
  west 
  of 
  north, 
  yet 
  

   the 
  cliffs 
  are 
  as 
  prominent 
  on 
  the 
  west 
  side 
  as 
  on 
  the 
  east. 
  When 
  

   the 
  lake 
  was 
  formed, 
  there 
  must 
  have 
  existed 
  a 
  ver^- 
  steep 
  slope, 
  if 
  

   not 
  an 
  actual 
  bluff', 
  where 
  the 
  cliffs 
  now 
  are, 
  which 
  shore 
  action, 
  

   greatly 
  aided 
  by 
  frost, 
  has 
  cut 
  back 
  into 
  the 
  typical 
  wave-cut 
  terrace. 
  

  

  How 
  such 
  a 
  bluff 
  might 
  be 
  formed 
  will 
  be 
  discussed 
  later. 
  

  

  