﻿240 
  Lahee 
  — 
  New 
  Fossiliferous 
  Horizon 
  and 
  Underlying 
  

  

  schists, 
  and 
  there 
  can 
  be 
  no 
  doubt 
  that 
  this 
  Fitch 
  Hill 
  granite 
  

   gneiss 
  is 
  intrusive 
  into, 
  and 
  therefore 
  younger 
  than, 
  the 
  Lyman 
  

   schist 
  group. 
  

  

  Unconformable 
  contact 
  with 
  Blueberry 
  Mountain 
  Series. 
  

   — 
  At 
  the 
  southern 
  contact 
  the 
  conditions 
  are 
  very 
  different 
  

   from 
  those 
  on 
  the 
  north. 
  Here 
  the 
  gneiss 
  rests 
  againsfc 
  a 
  body 
  

   of 
  sedimentary 
  rocks 
  which 
  are 
  much 
  less 
  metamorphosed 
  than 
  

   the 
  Lyman 
  schists. 
  The 
  lower 
  members 
  of 
  this 
  sedimentary 
  

   series 
  are 
  known 
  to 
  be 
  of 
  Niagaran 
  (Upper 
  Silurian) 
  age.* 
  

   They 
  were 
  formerly 
  called 
  Helderbergian. 
  

  

  While 
  the 
  southern 
  contact 
  region 
  does 
  receive 
  some 
  men- 
  

   tion 
  in 
  the 
  geological 
  literature, 
  the 
  references 
  are 
  vague. 
  

   Lambert 
  wrote 
  that 
  the 
  granite 
  gneiss 
  "broke 
  through" 
  the 
  

   sediments.f 
  Hitchcock 
  in 
  one 
  placed 
  says 
  it 
  " 
  cuts 
  off 
  " 
  the 
  

   " 
  Helderberg." 
  Elsewhere 
  he 
  says 
  it 
  " 
  may 
  be 
  followed 
  to 
  

   close 
  contact 
  with 
  the 
  limestone 
  " 
  (Niagaran) 
  ;§ 
  and 
  again, 
  

   " 
  Below 
  and 
  in 
  contact 
  with 
  the 
  fossils 
  on 
  Fitch 
  Hill 
  the 
  rock 
  

   is 
  a 
  chloritic 
  foliated 
  granite."! 
  On 
  the 
  same 
  page] 
  we 
  read, 
  

   the 
  " 
  synclinal 
  in 
  Littleton 
  rests 
  on 
  igneous 
  materials 
  " 
  ; 
  and 
  

   here, 
  too, 
  we 
  find 
  the 
  suggestion 
  of 
  an 
  unconformity 
  in 
  the 
  

   words 
  "basal 
  limestones," 
  meaning 
  the 
  Niagaran 
  limestone. 
  

  

  We 
  made 
  as 
  minute 
  an 
  examination 
  of 
  this 
  contact 
  as 
  we 
  

   did 
  of 
  the 
  northern 
  one. 
  No 
  dikes 
  nor 
  apophyses 
  of 
  any 
  sort 
  

   pass 
  from 
  the 
  gneiss 
  into 
  the 
  sediments, 
  and, 
  while 
  the 
  contact 
  

   has 
  several 
  broad 
  and 
  often 
  deep 
  jogs 
  or 
  indentations, 
  it 
  is 
  

   essentially 
  straight. 
  The 
  granite 
  gneiss 
  sometimes 
  remains 
  

   coarse 
  quite 
  up 
  to 
  the 
  sediments. 
  More 
  often, 
  however, 
  it 
  

   grades 
  into 
  a 
  somewhat 
  finer 
  rock. 
  In 
  one 
  place 
  where 
  the 
  

   gneiss 
  adjoined 
  this 
  finer 
  rock, 
  the 
  former 
  seemed 
  to 
  pass 
  into 
  

   the 
  latter 
  by 
  concentric 
  layers 
  about 
  a 
  roundish 
  projection 
  of 
  

   fresh 
  gneiss 
  (see 
  fig. 
  5). 
  There 
  were 
  several 
  such 
  bowlder-like 
  

   masses 
  of 
  fresh 
  gneiss 
  partly 
  or 
  wholly 
  wrapped 
  in 
  layers 
  of 
  

   the 
  same 
  material, 
  more 
  and 
  more. 
  weathered 
  outward. 
  From 
  

   these 
  facts 
  and 
  from 
  a 
  microscopic 
  inspection 
  of 
  the 
  'finer 
  

   rock,' 
  we 
  have 
  been 
  led 
  to 
  infer 
  that 
  this 
  contact 
  is 
  an 
  uncon- 
  

   formity 
  ; 
  that 
  the 
  granite 
  gneiss, 
  preceding 
  the 
  deposition 
  of 
  

   the 
  Niagaran, 
  broke 
  down, 
  by 
  disintegration 
  without 
  much 
  

   decomposition, 
  into 
  a 
  feldspathic 
  gravel 
  or 
  coarse 
  sand, 
  now 
  an 
  

   arkose 
  (the 
  ' 
  finer 
  rock 
  ') 
  ; 
  and 
  that 
  in 
  some 
  places 
  we 
  have 
  

   the 
  original 
  spheroidal 
  weathering 
  preserved 
  and 
  bevelled 
  

   across 
  by 
  the 
  present 
  land 
  surface 
  (fig. 
  4). 
  Further 
  support 
  of 
  

  

  * 
  See 
  Hitchcock's 
  Geology 
  of 
  Littleton, 
  pp. 
  4-6, 
  and 
  his 
  New 
  Studies 
  in 
  

   the 
  Ammonoosuc 
  District, 
  p. 
  462. 
  

  

  f 
  Lambert, 
  A. 
  E. 
  : 
  A 
  Trilobite 
  from 
  Littleton, 
  etc., 
  in 
  Hitchcock's 
  Geol- 
  

   ogy 
  of 
  Littleton, 
  p. 
  34. 
  

  

  \ 
  Geology 
  of 
  Northern 
  New 
  England, 
  p. 
  15. 
  

  

  | 
  Geology 
  of 
  Littleton, 
  p. 
  17. 
  

  

  If 
  New 
  Studies 
  in 
  the 
  Ammonoosuc 
  District, 
  p. 
  465, 
  

  

  