﻿THE 
  EPICENTRAL 
  TRACT. 
  137 
  

  

  one 
  direction 
  from 
  the 
  crest, 
  was 
  once 
  continuous 
  with 
  the 
  precisely 
  

   similar 
  plateau 
  which 
  slopes 
  up 
  from 
  the 
  foot 
  of 
  the 
  range 
  on 
  the 
  

   other 
  direction. 
  These 
  ranges 
  are 
  in 
  fact 
  fault 
  scarps, 
  due 
  to 
  unequal 
  

   elevation 
  along 
  faults, 
  by 
  which 
  the 
  rocks 
  composing 
  the 
  range 
  have 
  

  

  been 
  split. 
  

  

  The 
  history 
  of 
  the 
  Assam 
  range, 
  consequently, 
  falls 
  into 
  three 
  

  

  stao 
  . 
  es 
  . 
  First, 
  an 
  old 
  land 
  surface 
  which 
  had 
  long 
  been 
  exposed 
  to 
  

  

  denudation 
  and 
  worn 
  down 
  till 
  the 
  agencies 
  of 
  subaerial 
  denudation 
  

   had 
  almost 
  ceased 
  to 
  produce 
  any 
  further 
  change, 
  and 
  the 
  land 
  

   surface 
  was 
  reduced 
  to 
  that 
  aspect 
  for 
  which 
  Prof. 
  W. 
  M. 
  Davis 
  has 
  

   proposed 
  the 
  name 
  ' 
  peneplain.' 
  Then 
  this 
  land 
  surface 
  was 
  elevated, 
  

   and 
  the 
  elevation 
  was 
  unequal, 
  the 
  rocks 
  were 
  broken 
  through 
  by 
  

   fissures 
  of 
  which 
  one 
  side 
  was 
  raised 
  further 
  than 
  the 
  other, 
  and 
  instead 
  

   of 
  a 
  uniform 
  surface 
  the 
  old 
  peneplain 
  was 
  broken 
  up 
  into 
  portions 
  

   which 
  lay 
  at 
  different 
  heights. 
  Finally, 
  the 
  elevation 
  of 
  the 
  plateau 
  as 
  

   a 
  whole 
  gave 
  the 
  streams 
  a 
  chance 
  of 
  eroding 
  once 
  more, 
  deep 
  

   gorges 
  were 
  driven 
  into 
  the 
  range, 
  and 
  in 
  parts 
  the 
  re-shaping 
  of 
  the 
  

   surface 
  has 
  gone 
  so 
  far 
  that 
  almost 
  all 
  trace 
  of 
  the 
  old 
  peneplain 
  is 
  

   lost. 
  

  

  One 
  point 
  more 
  may 
  be 
  noticed, 
  that, 
  so 
  far 
  as 
  the 
  main 
  mass 
  

   of 
  these 
  hills 
  is 
  concerned, 
  the 
  last 
  elevation 
  does 
  not 
  seem 
  to 
  

   have 
  been 
  accompanied 
  by 
  any 
  marked 
  compression. 
  Undulations 
  

   of 
  the 
  plateau, 
  sometimes 
  of 
  considerable 
  height, 
  have 
  been 
  formed, 
  

   besides 
  the 
  fault 
  scarps, 
  and 
  these 
  may 
  indicate 
  some 
  compression. 
  

   It 
  is 
  possible, 
  too, 
  that 
  the 
  faults 
  are 
  reversed 
  ones, 
  and 
  so 
  in- 
  

   dicate 
  compression 
  to 
  a 
  small 
  degree, 
  but 
  on 
  this 
  point 
  there 
  is 
  no 
  

   evidence 
  available. 
  Any 
  way, 
  the 
  amount 
  of 
  compression 
  which 
  has 
  

   taken 
  place, 
  if 
  any, 
  must 
  be 
  small 
  in 
  the 
  main 
  mass 
  of 
  the 
  range. 
  

   On 
  the 
  southern 
  edge, 
  where 
  we 
  come 
  into 
  the 
  region 
  of 
  tertiary 
  and 
  

   cretaceous 
  sedimentary 
  rocks 
  we 
  also 
  enter 
  a 
  region 
  where 
  there 
  has 
  

   been 
  a 
  certain 
  amount 
  of 
  compression, 
  as 
  evidenced 
  by 
  the 
  folding 
  

   of 
  the 
  strata. 
  Though 
  the 
  amount 
  of 
  compression 
  undergone 
  is 
  

   small 
  in 
  proportion 
  to 
  that 
  which 
  the 
  rocks 
  of 
  the 
  Himalayas 
  have 
  

   undergone, 
  it 
  is 
  not 
  inconsiderable 
  and 
  points 
  to 
  an 
  approach 
  

  

  ( 
  '37 
  ) 
  

  

  