﻿] 
  6 
  EOOTE 
  : 
  GEOLOGY 
  OF 
  MADRAS. 
  

  

  a. 
  — 
  Marine 
  and 
  estuarine 
  alluvium. 
  

   The 
  strip 
  of 
  land 
  lying" 
  along- 
  the 
  coast 
  southward 
  from 
  Madras 
  as 
  

   far 
  as 
  Sadras, 
  offers 
  undeniable 
  evidence 
  of 
  a 
  slight 
  elevation 
  of 
  the 
  

   land 
  having 
  taken 
  place 
  in 
  comparatively 
  recent 
  times. 
  The 
  evidences 
  

   of 
  this 
  elevatory 
  movement 
  consist 
  in 
  the 
  presence 
  of 
  beds 
  abounding 
  in 
  

   the 
  remains 
  of 
  marine 
  and 
  estuarine 
  shells 
  of 
  existing 
  species 
  at 
  consi- 
  

   _, 
  . 
  , 
  derable 
  distances 
  from 
  the 
  coast. 
  The 
  whole 
  of 
  

  

  Marine 
  strata 
  under- 
  

   lying 
  Madras. 
  Madras 
  appears 
  to 
  be 
  built 
  on 
  such 
  beds 
  which 
  

  

  have 
  been 
  laid 
  open 
  at 
  various 
  places 
  in 
  the 
  excavation 
  of 
  wells. 
  Thus, 
  

   for 
  example 
  ; 
  the 
  two 
  well- 
  sections, 
  given 
  by 
  Captain 
  Newbold 
  in 
  his 
  

   Summary 
  of 
  the 
  Geology 
  of 
  Southern 
  India, 
  sunk 
  

   in 
  1832 
  at 
  the 
  Land 
  Custom 
  House, 
  about 
  three- 
  

   fourths 
  of 
  a 
  mile 
  inland 
  from 
  the 
  sea, 
  reached 
  a 
  bed 
  of 
  black 
  clay 
  with 
  

   marine 
  shells 
  at 
  depths 
  of 
  13 
  and 
  16 
  feet, 
  and 
  came 
  upon 
  the 
  gneiss 
  

   at 
  depths 
  of 
  51 
  feet 
  8 
  inches, 
  and 
  55 
  feet 
  respectively. 
  

  

  The 
  succession 
  of 
  formations 
  shown 
  in 
  the 
  deeper 
  of 
  the 
  two 
  

   wells 
  was 
  — 
  

  

  1. 
  Sand 
  and 
  clay.... 
  ... 
  

  

  2. 
  Light 
  colored 
  sand 
  and 
  clay 
  

  

  3. 
  Stiff 
  clay 
  

  

  4. 
  River 
  sand 
  

  

  5. 
  Black 
  clay 
  with 
  sand 
  and 
  shells 
  

  

  6. 
  Blue 
  clay 
  with 
  sand 
  and 
  lime 
  and 
  pieces 
  of 
  -\ 
  

  

  iron 
  stone 
  ... 
  ... 
  ... 
  ... 
  j 
  

  

  7. 
  Granite 
  aud 
  quartz 
  rubble 
  ... 
  

  

  8. 
  Clay 
  and 
  gravel 
  mixed 
  with 
  broken 
  granite, 
  } 
  g 
  q 
  

  

  quartz, 
  mica, 
  &c. 
  ... 
  ... 
  ... 
  ) 
  

  

  Total 
  ... 
  55 
  

  

  ft. 
  

  

  iu. 
  

  

  3 
  

  

  

  

  1 
  

  

  

  

  3 
  

  

  6 
  

  

  5 
  

  

  6 
  

  

  20 
  

  

  

  

  12 
  

  

  6 
  

  

  

  

  G 
  

  

  Mr. 
  B. 
  G. 
  Babington, 
  in 
  a 
  paper 
  referred 
  to 
  at 
  page 
  5, 
  describes 
  

   the 
  following 
  sequence 
  of 
  formations 
  as 
  occurring 
  in 
  a 
  well-section 
  sunk 
  

   in 
  Colonel 
  Marshall's 
  garden 
  at 
  a 
  distance 
  of 
  two 
  miles 
  from 
  the 
  shore 
  : 
  — 
  

   " 
  From 
  the 
  surface 
  for 
  5 
  feet 
  there 
  is 
  a 
  stratum 
  of 
  brown 
  clay 
  chiefly 
  

   intermixed 
  with 
  sand. 
  Then 
  follows 
  a 
  stratum 
  of 
  bluish 
  black 
  clay, 
  in 
  

   which 
  at 
  the 
  distance 
  of 
  21 
  feet, 
  there 
  is 
  a 
  thin 
  and 
  scattered 
  layer 
  of 
  

  

  ( 
  10 
  ) 
  

  

  