﻿NIAGARA 
  FALLS 
  AND 
  VICINITY 
  35 
  

  

  these 
  deposits, 
  particularly 
  the 
  hmestones, 
  point 
  to 
  a 
  considerable 
  

   distance 
  from 
  the 
  shore 
  hne, 
  we 
  are 
  by 
  no 
  means 
  at 
  liberty 
  to 
  as- 
  

   sume 
  that 
  no 
  shore 
  formations 
  accumulated 
  during 
  this 
  period. 
  In 
  

   fact, 
  it 
  would 
  be 
  difficult 
  to 
  understand 
  the 
  non-accumulation 
  of 
  ter- 
  

   rigenous 
  material 
  along 
  the 
  shores 
  of 
  any 
  land 
  during 
  any 
  period 
  of 
  

   the 
  earth's 
  history 
  unless 
  such 
  land 
  was 
  without 
  even 
  moderate 
  

   relief. 
  As 
  will 
  be 
  shown 
  in 
  chapter 
  3 
  there 
  are 
  reasons 
  for 
  suppos- 
  

   ing 
  that 
  a 
  considerable 
  land 
  barrier 
  existed 
  in 
  the 
  north 
  as 
  well 
  

   as 
  the 
  east 
  and 
  southeast, 
  and 
  thus 
  we 
  may 
  assume 
  that 
  shore 
  de- 
  

   posits 
  of 
  terrigenous 
  material 
  were 
  formed 
  while 
  the 
  limestones 
  were 
  

   accumulating 
  in 
  the 
  clearer 
  waters. 
  That 
  the 
  shores 
  of 
  this 
  period 
  

   did 
  not 
  consist 
  of 
  Medina 
  sandstone 
  is 
  indicated 
  by 
  the 
  absence 
  of 
  

   any 
  such 
  material 
  in 
  the 
  shales 
  of 
  either 
  the 
  Clinton 
  or 
  Niagara 
  

   series. 
  It 
  is 
  highly 
  probable 
  that 
  the 
  shore 
  was 
  still 
  formed 
  by 
  the 
  

   old 
  crystalline 
  highlands, 
  and 
  that 
  the 
  accumulating 
  Clinton 
  and 
  

   Niagara 
  sediments 
  overlapped 
  and 
  completely 
  buried 
  the 
  Medina 
  

   beds. 
  The 
  limestones 
  are 
  chiefly 
  fragmental 
  in 
  origin, 
  being 
  com- 
  

   posed 
  of 
  calcareous 
  and 
  magnesian 
  sands. 
  These, 
  as 
  will 
  be 
  shown 
  

   later, 
  were 
  largely 
  derived 
  from 
  the 
  destruction 
  of 
  coral 
  reefs 
  and 
  

   shells 
  growing 
  in 
  the 
  immediate 
  neighborhood. 
  They 
  indicate 
  shal- 
  

   low 
  water, 
  a 
  conclusion 
  emphasized 
  by 
  the 
  occurrence 
  of 
  well 
  

   marked 
  cross-bedding 
  structure 
  in 
  some 
  of 
  the 
  beds 
  of 
  limestone. 
  

   We 
  may 
  assume 
  a 
  gradual 
  passage 
  from 
  pure 
  calcareous 
  beds 
  to 
  

   beds 
  consisting 
  more 
  and 
  more 
  of 
  terrigenous 
  detritus 
  as 
  we 
  ap- 
  

   proach 
  the 
  old 
  shore 
  line, 
  where 
  quartz 
  sands 
  probably 
  constituted 
  

   the 
  chief 
  material 
  of 
  the 
  deposits. 
  

  

  ■We 
  may 
  obtain 
  an 
  approximate 
  indication 
  of 
  the 
  former 
  extent 
  

   of 
  these 
  strata 
  if 
  an 
  attempt 
  be 
  made 
  to 
  restore 
  the 
  portions 
  which 
  

   must 
  have 
  been 
  removed 
  by 
  erosion. 
  We 
  may 
  consider 
  the 
  Clinton 
  

   and 
  Niagara 
  as 
  a 
  unit, 
  assuming 
  that 
  near 
  the 
  old 
  shore 
  their 
  beds 
  

   were 
  practicably 
  indistinguishable. 
  The 
  average 
  dip 
  of 
  the 
  strata 
  

   of 
  this 
  region 
  is 
  25 
  feet 
  to 
  the 
  mile 
  (a 
  moderate 
  estimate, 
  as 
  the 
  dip 
  

   ranges 
  up 
  to 
  40 
  feet), 
  and 
  the 
  base 
  of 
  the 
  Clinton-Niagara 
  is 
  ap- 
  

   proximately 
  400 
  feet 
  above 
  sea 
  level. 
  Continuing 
  this 
  dip 
  north- 
  

   ward 
  for 
  a 
  hundred 
  miles 
  to 
  where 
  the 
  present 
  borders 
  of 
  the 
  old- 
  

   land 
  are 
  exposed, 
  the 
  base 
  of 
  this 
  group 
  would 
  have 
  risen 
  2900 
  feet 
  

  

  