﻿12 
  BOSE 
  : 
  GEOLOGY 
  OF 
  THE 
  LOWER 
  NARBADA 
  VALLEY. 
  

  

  masses 
  of 
  segregated 
  silica 
  are 
  thus 
  occasionally 
  associated 
  with 
  the 
  lime- 
  

   stone. 
  The 
  laminae 
  are 
  sometimes 
  beautifully 
  parallel, 
  but 
  generally 
  

   still 
  more 
  beautifully 
  wavy 
  or 
  concentric. 
  This 
  last-named 
  structure, 
  

   however, 
  would 
  appear 
  to 
  be 
  confined 
  to 
  the 
  uppermost 
  beds. 
  I 
  found 
  

   such 
  to 
  be 
  the 
  case 
  in 
  several 
  pits. 
  The 
  chert-tubes 
  are 
  irregularly 
  cir- 
  

   cular 
  in 
  section, 
  with 
  a 
  nucleus 
  of 
  the 
  same 
  material 
  in 
  the 
  centre. 
  The 
  

   collections 
  of 
  concentric 
  tubes 
  are 
  not 
  unlike 
  the 
  c 
  ' 
  geodes 
  " 
  in 
  the 
  Deccan 
  

   trap, 
  and, 
  being 
  certainly 
  of 
  similar 
  origin, 
  may 
  be 
  conveniently 
  de- 
  

   scribed 
  under 
  that 
  name. 
  Each 
  geode 
  is 
  from 
  3 
  to 
  4 
  inches 
  in 
  diameter, 
  

   and 
  consists 
  of 
  7 
  to 
  9 
  laminae 
  of 
  chert 
  alternating 
  with 
  limestone. 
  When 
  

   the 
  bands 
  are 
  parallel 
  they 
  are 
  inclined 
  at 
  all 
  angles 
  to 
  the 
  horizon 
  ; 
  and 
  

   the 
  inclination 
  may 
  sometimes 
  coincide 
  with 
  the 
  dip 
  of 
  bedding 
  ; 
  but, 
  as 
  

   it 
  does 
  not 
  always 
  do 
  so, 
  the 
  former 
  is 
  a 
  very 
  unreliable 
  guide. 
  The 
  true 
  

   dip 
  is 
  best 
  seen 
  where 
  the 
  chert 
  banding 
  is 
  absent, 
  as 
  near 
  Barwai, 
  where 
  

   the 
  average 
  inclination 
  is 
  45° 
  westward. 
  At 
  other 
  places, 
  as, 
  for 
  in- 
  

   stance, 
  near 
  Jhirpania, 
  in 
  the 
  Dhar 
  forest 
  (Nimanpur), 
  the 
  bedding-dip 
  

   (40° 
  — 
  55°, 
  to 
  N.-20°-W.) 
  crosses 
  the 
  lamination 
  dip 
  at 
  a 
  high 
  angle. 
  

   But 
  usually 
  the 
  former 
  is 
  quite 
  obscured 
  by 
  the 
  latter. 
  If 
  the 
  bands 
  

   cannot 
  be 
  trusted 
  to 
  represent 
  bedding, 
  it 
  is 
  equally 
  doubtful 
  if 
  they 
  

   " 
  generally 
  correspond 
  to 
  original 
  cleavage 
  planes," 
  as 
  they 
  have 
  been 
  

   considered 
  to 
  do 
  by 
  Mr. 
  Blanf 
  ord 
  ; 
  for 
  the 
  dips 
  of 
  the 
  laminae 
  were 
  found 
  

   to 
  be 
  neither 
  so 
  generally 
  high, 
  nor, 
  if 
  high, 
  so 
  very 
  steady 
  as 
  would 
  

   justify 
  such 
  a 
  conclusion. 
  But 
  that 
  they 
  may 
  sometimes 
  correspond 
  to 
  . 
  

   cleavage 
  planes, 
  as 
  they 
  may 
  also 
  to 
  bedding 
  planes, 
  is 
  evident. 
  

  

  The 
  breccia, 
  which 
  is 
  the 
  other 
  important 
  constituent 
  of 
  the 
  series, 
  is 
  

   a 
  very 
  massive 
  rock, 
  generally 
  with 
  but 
  little 
  trace 
  of 
  bedding. 
  In 
  colour 
  

   it 
  is 
  characteristically 
  yellowish 
  or 
  yellowish-brown. 
  Along 
  faults 
  it 
  is 
  

   never 
  missed, 
  and, 
  abutting 
  against 
  darker-coloured 
  metamorphics, 
  pre- 
  

   sents 
  a 
  beautiful 
  contrast, 
  and 
  may 
  be 
  traced 
  as 
  far 
  as 
  the 
  eye 
  can 
  see, 
  if 
  

   the 
  fault-line 
  happens 
  to 
  be 
  in 
  an 
  open 
  place, 
  as, 
  for 
  instance, 
  the 
  bed 
  of 
  

   a 
  large 
  river, 
  such 
  as 
  the 
  Narbada. 
  The 
  matrix 
  is 
  hornstone 
  or 
  jasper 
  ; 
  

   and 
  fragments 
  of 
  milk-white 
  quartzite 
  are 
  dissemminated 
  through 
  it. 
  

   Away 
  from 
  faults, 
  the 
  breccia 
  alternates 
  with 
  the 
  limestone, 
  but 
  there 
  

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  12 
  ) 
  

  

  