﻿74 
  

  

  PEOE. 
  T. 
  G. 
  BONNET 
  OlST 
  TWO 
  TEAVEESES 
  OF 
  THE 
  

  

  band 
  of 
  arkose 
  may 
  possibly 
  exist 
  at 
  the 
  base 
  of 
  the 
  former, 
  it 
  is 
  

   difficult 
  in 
  the 
  field 
  to 
  put 
  one's 
  finger 
  on 
  the 
  actual 
  junction. 
  But 
  

   this 
  neutral 
  zone 
  is 
  at 
  most 
  only 
  a 
  very 
  few 
  feet 
  in 
  extent, 
  and 
  is 
  

   no 
  proof 
  of 
  transitional 
  metamorphism, 
  for 
  it 
  is 
  merely 
  a 
  local 
  acci- 
  

   dent, 
  where 
  Dame 
  Nature 
  has 
  " 
  smudged" 
  her 
  handwriting. 
  Only 
  

   a 
  few 
  dozen 
  yards 
  of 
  the 
  Carboniferous 
  rock 
  are 
  exposed, 
  then 
  

   comes 
  some 
  more 
  debris, 
  after 
  which 
  the 
  crushed 
  crystalline 
  rock 
  

   reappears. 
  In 
  both 
  the 
  cleavage 
  maintains 
  the 
  same 
  general 
  direc- 
  

   tion, 
  and 
  is 
  obviously 
  due 
  to 
  one 
  (Post-Carboniferous) 
  set 
  of 
  move- 
  

   ments. 
  

  

  As 
  we 
  approach 
  the 
  village 
  of 
  Freney 
  the 
  crystalline 
  rock 
  gra- 
  

   dually 
  becomes 
  less 
  fissile 
  and 
  more 
  granitoid 
  in 
  character. 
  Just 
  

   beyond 
  Freney 
  is 
  the 
  second 
  infold 
  of 
  the 
  Carboniferous 
  group. 
  A 
  

   small 
  quarry 
  has 
  been 
  opened 
  in 
  a 
  slabby 
  rock, 
  with 
  sheen 
  surfaces 
  

   dipping 
  roughly 
  60° 
  E. 
  This, 
  at 
  the 
  time, 
  I 
  was 
  disposed 
  to 
  refer 
  

   to 
  the 
  old 
  crystalline 
  series 
  ; 
  but 
  microscopic 
  examination 
  makes 
  its 
  

   true 
  nature 
  rather 
  doubtful, 
  and 
  it 
  may 
  be 
  a 
  modified 
  igneous 
  rock 
  

   of 
  later 
  age. 
  This, 
  however, 
  is 
  not 
  very 
  material. 
  On 
  the 
  further 
  

   side 
  of 
  the 
  quarry 
  is 
  indubitable 
  Carboniferous 
  rock. 
  First 
  is 
  a 
  

   rather 
  micaceous 
  quartzose 
  grit, 
  then 
  a 
  black 
  slaty 
  rock, 
  like 
  that 
  

   already 
  mentioned, 
  in 
  which 
  presently 
  bands 
  of 
  conglomerate 
  or 
  

   breccia 
  and 
  of 
  arkose 
  are 
  intercalated 
  (Appendix, 
  p. 
  102). 
  

  

  The 
  eastern 
  side 
  of 
  the 
  trough 
  exhibits 
  indications 
  of 
  an 
  over- 
  

   thrust. 
  The 
  end 
  of 
  the 
  Carboniferous 
  infold 
  is 
  like 
  a 
  V 
  with 
  the 
  

   apex 
  pointing 
  eastward 
  and 
  one 
  limb 
  nearly 
  horizontal. 
  Between 
  

   the 
  latter 
  and 
  the 
  subjacent 
  crystalline 
  series 
  is 
  a 
  quartz 
  vein, 
  the 
  

   upper 
  surface 
  of 
  which 
  has 
  a 
  marked 
  slickensided 
  structure, 
  the 
  

   striae 
  running 
  eastwards. 
  The 
  effects 
  of 
  pressure 
  are 
  markedly 
  in- 
  

   dicated 
  even 
  in 
  the 
  coarsest 
  bands 
  of 
  the 
  infolded 
  rock. 
  The 
  frag- 
  

   ments 
  in 
  the 
  breccia 
  are 
  mostly 
  either 
  a 
  grey 
  granitoid 
  rock 
  or 
  a 
  

   greyish 
  banded 
  gneiss, 
  the 
  latter 
  exhibiting 
  " 
  sheen 
  surfaces 
  " 
  parallel 
  

   with 
  the 
  bands. 
  These 
  surfaces, 
  however, 
  bear 
  no 
  relation 
  to 
  the 
  

   cleavage 
  of 
  the 
  matrix, 
  for 
  they 
  point 
  in 
  all 
  directions. 
  Sometimes 
  

   in 
  two 
  adjacent 
  fragments 
  they 
  lie 
  almost 
  at 
  right 
  angles, 
  and 
  in 
  

   one 
  instance 
  I 
  noticed 
  three 
  adjacent 
  fragments 
  in 
  which 
  the 
  surfaces 
  

   were 
  rudely 
  parallel 
  to 
  the 
  faces 
  of 
  a 
  rhombohedron. 
  Hence 
  they 
  

   must 
  be 
  a 
  record 
  of 
  Pre-Carboniferous 
  earth-movements 
  *. 
  

  

  The 
  crystalline 
  rocks 
  east 
  of 
  this 
  infold 
  may 
  be 
  described 
  as 
  

   greenish 
  schist, 
  very 
  probably 
  granitoid 
  or 
  gneissoid 
  rock 
  modified 
  

   by 
  crushing 
  ; 
  but 
  nothing 
  noteworthy 
  occurred 
  before 
  we 
  reached 
  

   the 
  infold 
  of 
  Jurassic 
  rock 
  near 
  Le 
  Dauphin, 
  which 
  comes 
  down 
  

   below 
  the 
  level 
  of 
  the 
  Eomanche. 
  In 
  the 
  schist, 
  which 
  is 
  much 
  

   veined 
  with 
  quartz, 
  the 
  foliation 
  (cleavage) 
  strikes 
  between 
  N. 
  and 
  

   N.N.E., 
  and 
  dips 
  at 
  about 
  45° 
  on 
  the 
  east 
  side. 
  In 
  the 
  Jurassic 
  

   rock, 
  commonly 
  a 
  dark 
  slate, 
  cleavage 
  appears 
  to 
  be 
  coincident 
  with 
  

   bedding 
  ; 
  the 
  trough 
  extends 
  southwards 
  for 
  full 
  eight 
  miles, 
  cross- 
  

   ing 
  the 
  Yeneon 
  valley 
  at 
  Venose, 
  a 
  village 
  which 
  can 
  be 
  reached 
  

   from 
  Le 
  Dauphin 
  by 
  a 
  low 
  pass, 
  where 
  the 
  grassy 
  alps, 
  due 
  to 
  the 
  

  

  * 
  My 
  studies 
  of 
  the 
  Carboniferous 
  conglomerate 
  at 
  Vernayaz 
  have 
  led 
  me 
  to 
  

   a 
  similar 
  conclusion. 
  

  

  