﻿NIAGARA 
  FALLS 
  AND 
  VICINITY 
  IO5 
  

  

  Upper 
  shales. 
  Above 
  the 
  Bryozoan 
  beds 
  the 
  shale 
  is 
  soft, 
  and 
  

   more 
  evenly 
  and 
  finely 
  laminated, 
  splitting 
  often 
  into 
  thin 
  slabs 
  of 
  

   moderate 
  size. 
  Hard 
  calcareous 
  beds 
  are 
  generally 
  absent, 
  though 
  

   occasionally 
  found 
  near 
  the 
  top. 
  The 
  stratification 
  and 
  lamination 
  

   is 
  much 
  more 
  strongly 
  marked 
  in 
  this 
  than 
  in 
  any 
  other 
  division 
  of 
  

   this 
  rock. 
  When 
  freshly 
  broken, 
  the 
  shale 
  has 
  a 
  brownish 
  earthy 
  

   color, 
  which 
  changes 
  to 
  grayish 
  when 
  the 
  rock 
  decomposes 
  to 
  clay. 
  

   Fossils 
  are 
  rare, 
  those 
  found 
  being 
  seldom 
  well 
  preserved. 
  In 
  most 
  

   cases 
  the 
  shells 
  are 
  dissolved 
  away, 
  leaving 
  only 
  the 
  impressions 
  of 
  

   the 
  fossil, 
  which 
  from 
  compression 
  become 
  faint, 
  and 
  are 
  not 
  readily 
  

   recognized 
  without 
  careful 
  scrutiny. 
  The 
  most 
  common 
  remains 
  

   found 
  in 
  these 
  rocks 
  are 
  bivalve 
  mollusks 
  (pelecypods) 
  and 
  tri- 
  

   lobites. 
  Among 
  the 
  former 
  Pterinaea 
  emacerata 
  is 
  

   the 
  most 
  abundant, 
  while 
  Dalmanites 
  limulurus 
  is 
  the 
  

   chief 
  among 
  the 
  trilobites 
  of 
  these 
  beds. 
  Other 
  trilobites 
  also 
  occur 
  

   in 
  these 
  shales, 
  notably 
  Homalonotus 
  delphinocepha- 
  

   1 
  u 
  s 
  , 
  as 
  well 
  as 
  a 
  number 
  of 
  brachiopods. 
  

  

  Toward 
  the 
  top 
  fossils 
  become 
  rarer, 
  and 
  finally 
  are 
  wanting 
  al- 
  

   together. 
  The 
  shale 
  becomes 
  more 
  heavy 
  bedded, 
  and 
  calcareous 
  

   layers 
  begin 
  to 
  increase. 
  The 
  last 
  lo 
  feet 
  or 
  more 
  are 
  quite 
  calcare- 
  

   ous 
  and 
  compact, 
  and 
  have 
  an 
  irregular 
  fracture. 
  They 
  grade 
  up- 
  

   ward 
  into 
  the 
  basal 
  layers 
  of 
  the 
  Lockport 
  (Niagara) 
  limestone. 
  

  

  Lockport 
  (Niagara) 
  limestone 
  

  

  The 
  limestone 
  which 
  succeeds 
  the 
  Rochester 
  or 
  Niagara 
  shales 
  

   forms 
  the 
  summit 
  rock 
  of 
  the 
  series 
  from 
  the 
  edge 
  of 
  the* 
  Niagara 
  

   escarpment 
  to 
  south 
  of 
  the 
  falls. 
  It 
  consists 
  of 
  a 
  number 
  of 
  dis- 
  

   tinct 
  strata, 
  of 
  varying 
  characters, 
  most 
  of 
  them 
  very 
  poor 
  in 
  organic 
  

   remains. 
  The 
  total 
  thickness 
  exposed 
  in 
  the 
  Niagara 
  region 
  is 
  not 
  

   over 
  130 
  feet, 
  but 
  borings 
  show 
  that 
  the 
  thickness 
  of 
  the 
  limestone 
  

   lying 
  between 
  the 
  Rochester 
  shale 
  and 
  the 
  SaHna 
  shales 
  is 
  from 
  200 
  

   to 
  nearly 
  250 
  feet. 
  Some 
  of 
  the 
  upper 
  beds 
  of 
  this 
  Hmestone 
  mass 
  

   may 
  represent 
  the 
  Guelph 
  dolomite 
  and 
  others 
  may 
  belong 
  to 
  the 
  

   base 
  of 
  the 
  Salina 
  beds. 
  Nevertheless 
  we 
  may 
  confidently 
  assume 
  

   that 
  the 
  thickness 
  of 
  the 
  Lockport 
  limestone 
  in 
  this 
  region, 
  is 
  at 
  

   least 
  150 
  feet. 
  

  

  