﻿NIAGARA 
  FALLS 
  AND 
  VICINITY 
  33 
  

  

  The 
  Utica 
  shales 
  and 
  the 
  arenaceous 
  Lorraine 
  shales 
  which 
  fol- 
  

   low 
  on 
  the 
  Trenton 
  limestones 
  show 
  a 
  return 
  of 
  land-derived 
  de- 
  

   posits 
  due 
  probably 
  to 
  a 
  shoaling 
  of 
  the 
  water. 
  This 
  may 
  have 
  been 
  

   caused 
  by 
  an 
  upward 
  movement 
  of 
  the 
  sea 
  bottom 
  or 
  by 
  a 
  partial 
  

   withdrawal 
  of 
  the 
  water 
  into 
  deepening 
  oceanic 
  basins. 
  Some 
  

   abrupt 
  change 
  is 
  indicated 
  by 
  the 
  sudden 
  transition 
  from 
  limestone 
  

   to 
  black 
  shale. 
  Another 
  abrupt 
  change 
  occurred 
  at 
  the 
  close 
  of 
  the 
  

   Ordovicic 
  era, 
  as 
  indicated 
  by 
  the 
  marked 
  contrast 
  between 
  the 
  

   Lorraine 
  shales 
  and 
  the 
  Oneida 
  and 
  Medina 
  beds 
  which 
  immediately 
  

   succeed 
  them. 
  

  

  The 
  Siluric 
  deposits 
  of 
  this 
  region 
  began 
  as 
  shallow 
  water 
  accumu- 
  

   lations, 
  the 
  lowest 
  bed 
  being 
  the 
  Oswego 
  sandstone, 
  which 
  farther 
  

   east, 
  is 
  replaced 
  by 
  the 
  conglomerates 
  of 
  Oneida 
  county 
  and 
  the 
  

   Shawangunk 
  range. 
  The 
  marls 
  and 
  shales 
  of 
  the 
  Medina 
  series 
  

   succeed 
  these 
  sandstones 
  with 
  an 
  aggregate 
  thickness 
  exceeding 
  

   iioo 
  feet. 
  A 
  heavy 
  stratum 
  of 
  gray 
  quartzose 
  sandstone, 
  varying 
  

   in 
  thickness 
  up 
  to 
  25 
  or 
  30 
  feet, 
  separates, 
  in 
  the 
  Niagara 
  region, 
  

   the 
  lower 
  from 
  the 
  upper 
  Medina 
  shales 
  and 
  sandstones, 
  which 
  have 
  

   an 
  approximate 
  thickness 
  of 
  100 
  feet. 
  The 
  Clinton 
  shales 
  and 
  

   heavy 
  limestones 
  follow 
  on 
  the 
  Medina, 
  with 
  a 
  thickness 
  averaging 
  

   30 
  feet. 
  The 
  Rochester 
  shales, 
  with 
  a 
  thickness 
  of 
  60 
  to 
  70 
  feet, 
  

   follow 
  the 
  Clinton 
  limestones 
  and 
  are 
  in 
  turn 
  succeeded 
  by 
  the 
  Lock- 
  

   port 
  Hmestone, 
  whose 
  average 
  thickness, 
  obtained 
  from 
  well 
  records, 
  

   approximates 
  250 
  feet 
  in 
  this 
  region. 
  The 
  Salina 
  shales 
  succeeding 
  

   the 
  Niagara 
  beds 
  (Rochester 
  shales 
  and 
  Lockport 
  limestone) 
  have 
  

   an 
  aggregate 
  thickness 
  of 
  less 
  than 
  400 
  feet, 
  and 
  are 
  followed 
  by 
  the 
  

   Waterlime 
  and 
  the 
  Manlius 
  limestone, 
  the 
  former 
  averaging 
  50 
  feet 
  

   in 
  thickness, 
  the 
  latter 
  from 
  7 
  to 
  8 
  feet. 
  The 
  lowest 
  Devonic 
  beds 
  

   are 
  absent 
  in 
  this 
  region, 
  the 
  Onondaga 
  limestone 
  resting 
  directly 
  

   on 
  the 
  Manlius 
  beds, 
  there 
  being, 
  as 
  before 
  noted, 
  an 
  important 
  

   though 
  not 
  very 
  pronounced 
  unconformity 
  between 
  the 
  two. 
  A 
  

   glance 
  at 
  the 
  geologic 
  map 
  of 
  this 
  region 
  will 
  reveal 
  the 
  fact 
  that 
  the 
  

   lower 
  strata 
  rise 
  from 
  under 
  the 
  covering 
  newer 
  beds 
  on 
  the 
  north, 
  

   and 
  occupy 
  a 
  belt 
  of 
  country 
  of 
  greater 
  or 
  less 
  width 
  according 
  to 
  

   the 
  thickness 
  of 
  the 
  beds. 
  Where 
  they 
  come 
  to 
  an 
  end, 
  the 
  next 
  lower 
  

   beds 
  make 
  their 
  appearance. 
  The 
  discontinuation 
  of 
  the 
  higher 
  

  

  