﻿A. 
  W. 
  Giles 
  — 
  Niagara 
  Limestone 
  at 
  Rochester. 
  

  

  Aet. 
  XXI. 
  — 
  Brecciation 
  in 
  the 
  Niagara 
  Limestone 
  at 
  

   Rochester, 
  New 
  York; 
  by 
  Albekt 
  W. 
  Giles. 
  

  

  While 
  engaged 
  one 
  day 
  last 
  spring 
  in 
  unpacking 
  a 
  col- 
  

   lection 
  of 
  fossils 
  made 
  in 
  the 
  vicinity 
  of 
  Rochester, 
  N. 
  Y., 
  

   the 
  writer 
  was 
  surprised 
  to 
  note 
  that 
  a 
  number 
  of 
  speci- 
  

   mens 
  of 
  Niagara 
  limestone, 
  containing 
  both 
  minerals 
  and 
  

   fossils, 
  exhibited 
  excellent 
  brecciation. 
  Additional 
  speci- 
  

   mens 
  collected 
  during 
  the 
  past 
  summer 
  along 
  the 
  course 
  

   of 
  the 
  Genes 
  see 
  River 
  in 
  the 
  southern 
  part 
  of 
  the 
  city 
  of 
  

   Rochester 
  show 
  similar 
  brecciation. 
  A 
  careful 
  perusal 
  

   of 
  the 
  geological 
  literature 
  touching 
  on 
  the 
  Niagara 
  lime- 
  

   stone 
  of 
  western 
  New 
  York 
  failed 
  to 
  yield 
  any 
  informa- 
  

   tion 
  regarding 
  brecciation 
  in 
  this 
  formation. 
  This 
  lack 
  

   of 
  information 
  has 
  led 
  to 
  a 
  resurvey 
  of 
  the 
  writer's 
  field 
  

   notes 
  and 
  a 
  more 
  careful 
  examination 
  of 
  the 
  specimens. 
  

  

  The 
  Niagara 
  limestone, 
  more 
  specifically 
  named 
  Lock- 
  

   port 
  dolomite, 
  is 
  an 
  old 
  formation 
  geologically 
  and 
  has 
  

   had 
  a 
  long 
  and 
  checkered 
  career 
  in 
  geological 
  literature. 
  

   Among 
  early 
  descriptions 
  that 
  by 
  Prof. 
  Hall 
  is 
  the 
  most 
  

   widely 
  known 
  and 
  still 
  remains 
  the 
  best 
  (8). 
  1 
  He 
  gives 
  

   the 
  following 
  stratigraphic 
  sequence 
  : 
  

  

  5. 
  Thin-bedded 
  dark 
  gray 
  or 
  brownish 
  limestone. 
  Few 
  cavi- 
  

   ties. 
  Highly 
  bituminous. 
  Sometimes 
  contains 
  nodules 
  

   of 
  hornstone. 
  

  

  4. 
  Thick-bedded 
  dark 
  or 
  bluish 
  gray 
  limestone 
  with 
  irregular 
  

   cavities, 
  and 
  often 
  siliceous 
  accretions, 
  or 
  hornstone. 
  

   Surface 
  very 
  ragged 
  from 
  weathering. 
  Highly 
  bitu- 
  

   minous. 
  

  

  3. 
  A 
  lighter 
  colored 
  subcrystalline 
  mass, 
  very 
  irregularly 
  

   stratified, 
  contorted 
  and 
  concretionary. 
  

  

  2. 
  A 
  bluish 
  gray 
  subcrystalline 
  mass, 
  mostly 
  thin-bedded, 
  and 
  

   separated 
  by 
  seams 
  of 
  dark 
  shale. 
  

  

  1. 
  Gray 
  or 
  bluish 
  gray 
  siliceous 
  limestone; 
  hydraulic 
  lime- 
  

   stone, 
  or 
  beds 
  of 
  passage 
  from 
  the 
  shale 
  below. 
  

  

  The 
  "gray 
  or 
  bluish 
  gray 
  siliceous 
  limestone 
  ,, 
  at 
  the 
  

   base 
  of 
  the 
  formation 
  measures 
  from 
  4 
  to 
  10 
  feet 
  or 
  more 
  

   in 
  thickness 
  and 
  has 
  been 
  regarded 
  as 
  representing 
  a 
  

   gradual 
  gradation 
  from 
  the 
  Rochester 
  shale 
  below. 
  

   These 
  transitional 
  beds 
  are 
  best 
  seen 
  at 
  the 
  Goodman 
  

   street 
  quarries 
  in 
  the 
  northern 
  part 
  of 
  Rochester, 
  and 
  also 
  

  

  1 
  Eeference 
  numbers 
  in 
  the 
  text 
  apply 
  to 
  the 
  Bibliography 
  at 
  the 
  end 
  of 
  

   this 
  paper. 
  

  

  