﻿•30 
  EOOTE 
  : 
  GEOLOGY 
  OF 
  MADRAS. 
  

  

  manufacture 
  are 
  found 
  imbedded, 
  proving 
  that 
  man 
  had 
  set 
  foot 
  in 
  the 
  

   Peninsula 
  prior 
  to 
  the 
  formation 
  of 
  the 
  gravels 
  and 
  conglomerates 
  in 
  

   question. 
  These 
  gravels 
  and 
  conglomerates 
  form 
  the 
  upper 
  part 
  of 
  the 
  

   laterite 
  series, 
  which 
  is 
  therefore 
  referred 
  to 
  the 
  Quaternary 
  or 
  Recent 
  

   Period. 
  Some 
  of 
  the 
  principal 
  localities 
  yielding 
  these 
  implements 
  will 
  

   be 
  found 
  described 
  at 
  the 
  end 
  of 
  this 
  chapter. 
  

  

  Although 
  they 
  occupy 
  in 
  the 
  aggregate 
  an 
  area 
  of 
  several 
  hundred 
  

   square 
  miles, 
  the 
  lateritic 
  formations 
  are 
  generally 
  of 
  but 
  small 
  thickness, 
  

   often 
  merely 
  a 
  few 
  inches 
  in 
  depth, 
  but 
  still 
  they 
  give 
  so 
  much 
  character 
  

   to 
  the 
  surface 
  which 
  they 
  cover 
  that 
  they 
  are 
  deserving 
  of 
  more 
  attention 
  

   than 
  would 
  be 
  accorded 
  to 
  formations 
  of 
  less 
  individuality 
  in 
  mineral 
  

   and 
  structural 
  character. 
  

  

  The 
  lateritic 
  formations 
  generally 
  rest 
  unconformably 
  upon 
  much 
  

   older 
  fossiliferous 
  rocks 
  of 
  the 
  same 
  general 
  age 
  as 
  the 
  Rajmahal 
  rocks 
  

   of 
  Bengal 
  and 
  of 
  some 
  of 
  the 
  Oolitic 
  rocks 
  in 
  Kutch. 
  But 
  in 
  many 
  

   places 
  the 
  Rajmahal 
  rocks 
  are 
  overlapped 
  by 
  the 
  lateritic 
  formations, 
  

   which 
  then 
  rest 
  directly 
  on 
  the 
  metamorphic 
  rocks 
  (gneiss) 
  . 
  

  

  a. 
  — 
  Conglomerates, 
  Gravels, 
  fyc. 
  

  

  The 
  conglomerates 
  being 
  the 
  most 
  interesting 
  and 
  important 
  mem- 
  

  

  m 
  ..,',. 
  .. 
  . 
  ., 
  bers 
  of 
  the 
  whole 
  series 
  deserve 
  to 
  be 
  first 
  described. 
  

   Typical 
  laterite 
  at 
  the 
  

  

  Red 
  Hills. 
  rp^g 
  ^ 
  e( 
  j 
  Hills 
  conglomeratic 
  laterite, 
  which, 
  as 
  

  

  before 
  mentioned, 
  is 
  quite 
  typical, 
  occurs 
  in 
  several 
  detached 
  patches, 
  

   the 
  largest 
  being 
  at 
  the 
  northern 
  end 
  of 
  the 
  great 
  tank 
  around 
  

   the 
  village 
  of 
  Narraincoopum, 
  where 
  the 
  ancient 
  builders 
  of 
  the 
  so-called 
  

   Korumbar 
  rings, 
  availed 
  themselves 
  of 
  the 
  . 
  material 
  so 
  abundantly 
  at 
  

   hand 
  to 
  construct 
  a 
  great 
  number 
  of 
  their 
  rings 
  and 
  enclosed 
  kistvaens. 
  

   The 
  laterite 
  here 
  shows 
  to 
  perfection 
  its 
  peculiar 
  dark 
  glazed 
  cellular 
  

   surface 
  in 
  the 
  weathered 
  blocks, 
  while 
  the 
  freshly 
  quarried 
  masses 
  show 
  

   their 
  clayey 
  character 
  and 
  the 
  vermicular 
  and 
  cellular 
  cavities 
  filled 
  

   with 
  sand 
  or 
  sandy 
  clay. 
  The 
  undoubtedly 
  conglomeratic 
  nature 
  of 
  this 
  

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