﻿Report 
  of 
  the 
  State 
  Geologist. 
  677 
  

  

  off 
  by 
  the 
  sweep 
  of 
  the 
  earlier 
  formations 
  round 
  to 
  the 
  east, 
  

   bringing 
  the 
  Calciferous 
  to 
  the 
  lake 
  shore 
  in 
  southern 
  Peru, 
  fol- 
  

   lowed 
  in 
  turn 
  by 
  the 
  Potsdam 
  and 
  gneiss 
  in 
  Essex 
  county. 
  

  

  Trenton 
  limestone. 
  — 
  Exposures 
  of 
  the 
  Trenton 
  beds 
  are 
  quite 
  

   frequent 
  along 
  the 
  lake 
  shore," 
  or 
  close 
  to 
  it, 
  but 
  are 
  difficult 
  of 
  

   subdivision 
  because 
  of 
  the 
  usual 
  meagreness 
  of 
  the 
  exposures 
  and 
  

   the 
  similarity 
  of 
  the 
  different 
  beds. 
  The 
  main 
  phase 
  presented 
  

   is 
  a 
  black 
  limestone 
  with 
  a 
  pronounced 
  slaty 
  structure. 
  The 
  

   Black 
  Kiver 
  limestone 
  at 
  the 
  base 
  is 
  more 
  massive 
  than 
  most 
  

   of 
  the 
  Trenton, 
  and 
  is 
  seen 
  directly 
  capping 
  the 
  Chazy 
  at 
  a 
  

   number 
  of 
  localities, 
  notably 
  Chazy 
  township. 
  Much 
  of 
  the 
  

   Trenton 
  is 
  quite 
  fossiliferous, 
  but 
  near 
  the 
  base 
  is 
  a 
  series 
  of 
  beds 
  

   of 
  very 
  slaty 
  character, 
  in 
  which 
  fossils 
  are 
  for 
  the 
  most 
  part 
  

   absent. 
  

  

  In 
  Champiain 
  township 
  but 
  a 
  single 
  exposure 
  of 
  beds 
  referable 
  

   to 
  the 
  Trenton 
  is 
  found, 
  a 
  series 
  of 
  black 
  and 
  dark 
  blue 
  slates 
  

   and 
  slaty 
  limestones, 
  weathering 
  light 
  colored, 
  much 
  jointed, 
  the 
  

   seams 
  generally 
  filled 
  with 
  calcite, 
  whose 
  outcrop 
  extends 
  along 
  

   the 
  lake 
  for 
  a 
  quarter 
  of 
  a 
  mile 
  north 
  of 
  Point 
  au 
  Fer. 
  Search 
  

   for 
  fossils 
  was 
  unrewarded, 
  and 
  as 
  the 
  exposure 
  is 
  an 
  isolated 
  ' 
  

   one 
  the 
  reference 
  to 
  the 
  Trenton 
  rests 
  on 
  lithological 
  character 
  

   alone. 
  The 
  apparent 
  dip 
  is 
  seventy 
  degrees 
  to 
  the 
  northwest, 
  

   anomalous 
  for 
  the 
  region, 
  and 
  unexplained 
  till 
  similar 
  beds 
  

   on 
  Cumberland 
  Head 
  having 
  the 
  same 
  apparently 
  high 
  

   dip 
  were 
  examined. 
  Careful 
  examination 
  of 
  the 
  excellent 
  

   exposures 
  along 
  the 
  east 
  shore 
  of 
  Cumberland 
  bay 
  showed 
  

   the 
  true 
  dip 
  to 
  be 
  a 
  gentle 
  one 
  to 
  the 
  northeast, 
  and 
  that 
  

   the 
  apparent 
  high 
  dip 
  was 
  caused 
  by 
  a 
  series 
  of 
  joint 
  or 
  

   shear 
  planes, 
  commonly 
  only 
  an 
  inch 
  or 
  two 
  apart, 
  which 
  

   dip 
  to 
  the 
  southeast 
  at 
  angles 
  varying 
  from 
  thirty 
  to 
  

   sixty 
  degrees. 
  To 
  these 
  places 
  is 
  due 
  the 
  slaty 
  aspect 
  of 
  the 
  

   rock, 
  and 
  they 
  closely 
  mimic 
  bedding 
  planes. 
  A 
  series 
  of 
  

   nearly 
  vertical 
  joints 
  is 
  also 
  present. 
  The 
  true 
  dip 
  may 
  be 
  

   made 
  out 
  where 
  locally 
  the 
  shear 
  planes 
  are 
  less 
  pronounced, 
  

   or 
  where 
  there 
  are 
  variations 
  in" 
  the 
  color 
  of 
  the 
  differ- 
  

   ent 
  layers 
  across 
  which 
  the 
  shear 
  planes 
  cut. 
  Locally 
  some 
  

   slipping 
  has 
  taken 
  place 
  along 
  some 
  of 
  these 
  planes, 
  as 
  is 
  shown 
  

   by 
  the 
  bent 
  edges 
  of 
  the 
  layers 
  adjoining 
  the 
  plane, 
  and 
  their 
  

   non-correspondence 
  on 
  the 
  opposite 
  sides, 
  as 
  well 
  as 
  by 
  the 
  

  

  