﻿18 
  BOSE 
  : 
  GEOLOGY 
  OF 
  THE 
  LOWER 
  NARBADA 
  VALLEY. 
  

  

  vertical 
  at 
  the 
  first-mentioned 
  village. 
  This 
  abnormally 
  disturbed 
  condition 
  

   is 
  noticeable 
  for 
  a 
  mile 
  only 
  down 
  the 
  river. 
  Thence 
  to 
  Semli 
  (between 
  

   Pemgarh 
  and 
  Dhari 
  in 
  the 
  Dhar 
  forest) 
  , 
  the 
  dip 
  is 
  on 
  the 
  whole 
  steady 
  and 
  

   moderate, 
  pointing 
  in 
  general 
  to 
  the 
  south-west. 
  Here 
  an 
  important 
  

   synclinal 
  axis 
  is 
  crossed, 
  the 
  beds 
  beyond 
  to 
  the 
  west 
  of 
  it 
  dipping 
  in 
  

   a 
  north-eastern 
  direction. 
  This 
  dip 
  continues 
  to 
  the 
  western 
  termination 
  

   of 
  the 
  section 
  with 
  local 
  variations 
  both 
  in 
  amount 
  and 
  direction, 
  due 
  

   in 
  most 
  cases 
  to 
  doleritic 
  intrusions. 
  

  

  Igneous 
  intrusions. 
  — 
  The 
  lower 
  Narbada 
  Vindhyan 
  area 
  is, 
  according 
  

   to 
  Mr. 
  Mallet, 
  fi 
  the 
  only 
  one 
  yet 
  known 
  where 
  the 
  Vindhyans 
  have 
  

   undergone 
  the 
  intrusion 
  of 
  igneous 
  matter/' 
  1 
  

  

  Of 
  intrusions 
  on 
  a 
  large 
  scale, 
  the 
  dyke 
  north 
  of 
  Dhari 
  and 
  Rampura, 
  

   in 
  the 
  Dhar 
  forest, 
  is 
  the 
  most 
  conspicuous 
  instance. 
  It 
  is 
  elevated 
  

   about 
  100 
  feet 
  above 
  the 
  general 
  level 
  of 
  the 
  surrounding 
  Vindhyan 
  

   country, 
  and 
  is 
  about 
  5 
  miles 
  long. 
  The 
  hill 
  (known 
  as 
  Kaorabairi) 
  is 
  

   made 
  up 
  of 
  hexagonal 
  or 
  pentagonal 
  columns 
  of 
  basalt, 
  averaging 
  10 
  feet 
  

   in 
  length. 
  The 
  hexagonal 
  shape 
  prevails 
  ; 
  one 
  of 
  the 
  faces, 
  however, 
  is 
  

   generally 
  very 
  short. 
  At 
  the 
  extreme 
  eastern 
  end 
  of 
  the 
  dyke- 
  hill, 
  the 
  

   columns 
  are 
  perfectly 
  horizontal, 
  and 
  lie 
  with 
  their 
  longest 
  diameter 
  

   parallel 
  to 
  the 
  direction 
  in 
  which 
  the 
  hill 
  runs, 
  i. 
  e. 
  y 
  east 
  and 
  west. 
  A 
  

   few 
  yards 
  to 
  the 
  west, 
  however, 
  their 
  length 
  crosses 
  this 
  direction 
  very 
  

   nearly 
  at 
  right 
  angles, 
  and 
  they 
  are 
  either 
  horizontal 
  or 
  are 
  inclined, 
  

   though 
  at 
  a 
  low 
  angle, 
  to 
  the 
  horizon, 
  the 
  inclination 
  pointing 
  northward. 
  

   Horizontal 
  arrangement 
  of 
  columns 
  in 
  the 
  area 
  under 
  description 
  is 
  rare 
  ; 
  

   I 
  have 
  observed 
  only 
  two 
  more 
  instances 
  of 
  it, 
  to 
  be 
  mentioned 
  later 
  on. 
  

   It 
  establishes 
  the 
  intrusive 
  character 
  of 
  the 
  rock 
  beyond 
  a 
  question 
  ; 
  for 
  

   the 
  columns, 
  according 
  to 
  the 
  contraction 
  theory, 
  would 
  be 
  perpendicular 
  

   to 
  the 
  walls 
  of 
  the 
  fissure 
  in 
  which 
  the 
  rock 
  cooled 
  and 
  consolidated. 
  

  

  The 
  hill 
  rises 
  out 
  of 
  the 
  Vindhyans, 
  and 
  beds 
  of 
  these 
  are 
  to 
  be 
  seen 
  

   in 
  contact 
  with 
  the 
  dyke 
  at 
  several 
  places. 
  As 
  far 
  as 
  I 
  could 
  examine, 
  

   however, 
  I 
  did 
  not 
  notice 
  any 
  marks 
  of 
  exceptional 
  disturbance 
  or 
  altera- 
  

   tion 
  in 
  them, 
  their 
  dip 
  preserving 
  the 
  usual 
  north-eastern 
  direction. 
  

  

  1 
  «* 
  Memoirs," 
  Vol. 
  VII, 
  p. 
  79. 
  

  

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  18 
  ) 
  

  

  