﻿36 
  K)OTE 
  : 
  GEOLOGY 
  OF 
  MADRAS. 
  

  

  described, 
  which 
  in 
  the 
  southern 
  parts 
  of 
  the 
  area, 
  more 
  especially, 
  

   occur 
  but 
  in 
  detached 
  and 
  scattered 
  patches, 
  mostly 
  of 
  small 
  size. 
  

   These 
  gravel 
  and 
  sand 
  beds 
  may 
  be 
  best 
  seen 
  on 
  the 
  higher 
  grounds 
  

   to 
  the 
  north 
  and 
  west 
  of 
  Sripermatoor, 
  where 
  they 
  probably 
  obtain 
  

   their 
  maximum 
  thickness, 
  which, 
  however, 
  is 
  in 
  all 
  probability 
  but 
  

   small 
  and 
  cannot 
  be 
  estimated 
  at 
  much 
  more 
  than 
  20 
  feet. 
  The 
  upper 
  

   part 
  of 
  these 
  sands 
  is 
  frequently 
  pure, 
  or 
  mixed 
  only 
  with 
  laterite 
  pellets 
  

   in 
  very 
  varying 
  proportion. 
  When 
  pure, 
  it 
  often 
  shows 
  no 
  signs 
  what- 
  

   ever 
  of 
  bedding 
  ; 
  as, 
  for 
  example, 
  at 
  Illupur 
  (six 
  miles 
  north 
  of 
  Sri- 
  

   permatoor), 
  where 
  the 
  pure 
  reddish 
  sand 
  attains 
  a 
  thickness 
  of 
  more 
  

   than 
  5 
  feet, 
  as 
  shown 
  in 
  a 
  small 
  sand-pit. 
  

  

  In 
  a 
  section 
  offered 
  by 
  the 
  banks 
  of 
  a 
  small 
  nullah 
  about 
  two 
  miles 
  

   to 
  the 
  north-east 
  of 
  Illupur 
  and 
  a 
  little 
  south-east 
  of 
  Coopoor 
  village, 
  

   the 
  red 
  sandy 
  soil 
  is 
  distinctly 
  bedded, 
  the 
  bedding 
  being 
  shown 
  by 
  layers 
  

   of 
  laterite 
  pellets. 
  The 
  bedding 
  here 
  has 
  a 
  slight 
  south-easterly 
  dip. 
  

  

  The 
  lower 
  part 
  of 
  the 
  sands 
  is 
  sometimes 
  rather 
  clayey 
  and 
  charged 
  

  

  Difficulty 
  of 
  distiii- 
  w 
  ^ 
  n 
  kunkur 
  in 
  pipe-like 
  concretions, 
  and 
  it 
  then 
  

  

  of 
  tftaksE 
  over- 
  often 
  becomes 
  vei 
  7 
  difficult 
  to 
  distinguish 
  between 
  

  

  lying 
  clayey 
  beds. 
  them 
  and 
  the 
  under 
  l 
  ying 
  shaleS 
  f 
  tbe 
  Sriperma- 
  

  

  toor 
  series, 
  the 
  upper 
  beds 
  of 
  which 
  are 
  rarely 
  fossiliferous, 
  and 
  are 
  

   much 
  broken 
  up 
  at 
  the 
  top 
  and 
  filled 
  with 
  infiltrated 
  kunkur 
  concretions. 
  

   It 
  is 
  often 
  also 
  hard 
  to 
  distinguish 
  between 
  these 
  non-compact 
  

   lateritic 
  deposits, 
  when 
  they 
  rest 
  upon, 
  or 
  approach 
  close 
  to, 
  metamorphic 
  

   rocks, 
  and 
  the 
  reddish 
  sandy 
  soils 
  formed 
  by 
  the 
  decay 
  of 
  the 
  latter. 
  

   In 
  color 
  and 
  texture 
  they 
  are 
  often 
  quite 
  undistinguishable 
  to 
  the 
  

  

  naked 
  eye 
  ; 
  but 
  careful 
  searching 
  will 
  generally 
  

   Presence 
  of 
  quartzite 
  

   pebbles 
  in 
  lateritic 
  sand 
  solve 
  the 
  difficulty 
  by 
  discovery 
  in 
  the 
  true 
  late- 
  

   a 
  distinctive 
  sign. 
  

  

  ritic 
  sands 
  of 
  water-worn 
  fragments 
  of 
  quartzite 
  

  

  derived 
  indirectly 
  from 
  the 
  great 
  quartzite 
  beds 
  of 
  the 
  Kadapa 
  series, 
  

   which 
  cannot 
  of 
  course 
  occur 
  in 
  sands 
  formed 
  from 
  the 
  weathering 
  of 
  the 
  

   gneissic 
  rocks 
  underlying 
  them. 
  In 
  several 
  places 
  these 
  unconsolidated 
  

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  ) 
  

  

  