﻿82 
  THEOBALD 
  : 
  GEOLOGY 
  OF 
  PEGU. 
  

  

  sion. 
  The 
  Sitsyahn 
  shale 
  is 
  a 
  blue, 
  somewhat 
  clunchy 
  clay, 
  with 
  very 
  

   little 
  appearance 
  of 
  bedding 
  save 
  towards 
  its 
  upper 
  portion 
  where 
  sand- 
  

   stone 
  courses 
  begin 
  to 
  come 
  in. 
  When 
  dried, 
  it 
  is 
  of 
  a 
  very 
  pale 
  

   color, 
  and 
  cracks 
  and 
  falls 
  to 
  pieces 
  spontaneously, 
  as 
  some 
  of 
  the 
  

   Nummulitic 
  clays 
  likewise 
  do, 
  a 
  habit 
  which 
  depends 
  probably 
  on 
  the 
  

   homogenous 
  and 
  purely 
  argillaceous 
  character 
  and 
  fine 
  state 
  of 
  division 
  

   of 
  the 
  materials 
  composing 
  it. 
  It 
  bears 
  a 
  strong 
  resemblance 
  to 
  some 
  of 
  

   the 
  shales 
  of 
  the 
  Nummulitic 
  group, 
  though, 
  I 
  think, 
  rather 
  paler 
  in 
  

   color, 
  a 
  similarity 
  which 
  may 
  be 
  referred 
  to 
  its 
  probable 
  derivation 
  from 
  

   the 
  same 
  area 
  of 
  denudation 
  as 
  the 
  older 
  Nummulitic 
  clays. 
  It 
  is, 
  as 
  

   far 
  as 
  I 
  know, 
  entirely 
  unfossiliferous, 
  and 
  along 
  the 
  long 
  expanse 
  of 
  

   this 
  shale 
  below 
  Sitsyahn, 
  I 
  failed 
  to 
  detect 
  the 
  slightest 
  trace 
  of 
  any 
  

   organism 
  whatever, 
  though 
  the 
  character 
  of 
  the 
  rock 
  would 
  seem 
  to 
  be 
  

   well 
  adapted 
  for 
  the 
  preservation 
  of 
  fossils. 
  In 
  the 
  very 
  similar 
  clays 
  

   of 
  the 
  Nummulitic 
  group, 
  fossils 
  are 
  nearly 
  as 
  rare 
  ; 
  and 
  though 
  fossili- 
  

   ferous 
  in 
  places, 
  many 
  of 
  the 
  clays 
  higher 
  in 
  the 
  present 
  series 
  exhibit 
  

   a 
  similar 
  deficiency 
  ; 
  but 
  the 
  complete 
  absence 
  of 
  any 
  fossils 
  whatever 
  

   through 
  so 
  great 
  a 
  thickness 
  of 
  rock 
  well 
  adapted 
  for 
  their 
  preservation, 
  

   is 
  an 
  undoubted 
  feature 
  of 
  this 
  Sitsyahn 
  shale. 
  Even 
  where 
  a 
  large 
  

   expanse 
  of 
  the 
  shale 
  is 
  uncovered, 
  its 
  bedding 
  is 
  scarcely 
  perceptible, 
  

   but 
  can 
  be 
  estimated 
  from 
  the 
  occasional 
  presence 
  of 
  irregular 
  layers 
  

   of 
  fibrous 
  marl, 
  or 
  by 
  layers 
  of 
  hard 
  yellow 
  marl 
  traversed 
  by 
  shrinkage 
  

   seams 
  or 
  septaria 
  cracks 
  filled 
  by 
  carbonate 
  of 
  lime. 
  The 
  fibrous 
  marl 
  

   is 
  clearly 
  a 
  cotemporaneous 
  sedimentary 
  bed 
  in 
  which 
  the 
  presence 
  of 
  

   lime 
  has 
  permitted 
  the 
  development 
  of 
  this 
  fibrous 
  structure, 
  at 
  right 
  

   angles 
  to 
  the 
  planes 
  of 
  bedding, 
  the 
  result 
  of 
  a 
  sort 
  of 
  crystallizing 
  

   process, 
  dependant 
  on 
  the 
  composition 
  of 
  the 
  layer 
  affected, 
  and 
  in 
  

   which 
  the 
  amount 
  of 
  lime 
  varies 
  from 
  that 
  present 
  in 
  an 
  ordinary 
  marl, 
  

   to 
  that 
  of 
  a 
  tolerably 
  pure 
  limestone. 
  

  

  Prome 
  beds. 
  — 
  Above 
  the 
  Sitsyahn 
  shales 
  a 
  vast 
  series 
  of 
  beds 
  comes 
  

   in 
  of 
  shales 
  and 
  sandstone, 
  many 
  of 
  which 
  contain 
  fossils 
  in 
  abundance. 
  

   These 
  beds 
  rest 
  conformably 
  on 
  the 
  Sitsyahn 
  shales, 
  which 
  are 
  merely 
  

  

  ( 
  *70 
  ) 
  

  

  