﻿Appalachian 
  Geosyncline. 
  463 
  

  

  Reconstruction 
  of 
  Physiography 
  and 
  Climate 
  of 
  the 
  

   Catskill 
  Delta. 
  

  

  Comparison 
  of 
  the 
  Catskill 
  and 
  Skimnemunk 
  with 
  the 
  Siwalik 
  

  

  formation. 
  

  

  A 
  formation 
  strikingly 
  suggestive 
  in 
  connection 
  with 
  the 
  

   present 
  subject, 
  and 
  one 
  in 
  regard 
  to 
  which 
  the 
  interpretation 
  

   of 
  subaerial 
  origin 
  has 
  found 
  general 
  acceptance 
  because 
  of 
  

   the 
  clear 
  indication 
  of 
  the 
  fossil 
  record, 
  is 
  the 
  Siwalik 
  forma- 
  

   tion 
  of 
  the 
  sub-Himalayas. 
  In 
  order 
  to 
  show 
  the 
  similarities 
  

   to 
  the 
  Oneonta, 
  Catskill, 
  and 
  Skunnemunk 
  formations, 
  a 
  short 
  

   description 
  of 
  the 
  Siwalik 
  will 
  be 
  given. 
  These 
  are 
  Neocene 
  

   deposits 
  upwards 
  of 
  fifteen 
  thousand 
  feet 
  in 
  thickness, 
  skirting 
  

   the 
  southern 
  side 
  of 
  the 
  Himalayas. 
  They 
  were 
  laid 
  down 
  as 
  

   alluvial 
  outwash 
  from 
  the 
  rising 
  mountains 
  and 
  have 
  become 
  

   exposed 
  through 
  being 
  themselves 
  upturned 
  and 
  eroded 
  in 
  

   the 
  latest 
  movements. 
  Medlicott 
  and 
  Blanford 
  describe 
  the 
  

   Siwalik 
  formations 
  as 
  follows 
  : 
  

  

  " 
  Sandstone 
  immensely 
  preponderates 
  in 
  the 
  Sub-Himalayan 
  

   deposits, 
  and 
  is 
  of 
  a 
  very 
  persistent 
  type 
  from 
  end 
  to 
  end 
  of 
  the 
  

   region 
  and 
  from 
  top 
  to 
  bottom 
  of 
  the 
  series. 
  Its 
  commonest 
  

   form 
  is 
  undistinguishable 
  from 
  the 
  rock 
  of 
  corresponding 
  age 
  

   known 
  as 
  Mollasse 
  in 
  the 
  Alps, 
  of 
  a 
  clear 
  pepper 
  and 
  salt 
  grey, 
  

   sharp 
  and 
  fine 
  in 
  grain, 
  generally 
  soft, 
  and 
  in 
  very 
  massive 
  beds. 
  

   The 
  whole 
  Middle 
  and 
  Lower 
  Siwaliks 
  are 
  formed 
  of 
  this 
  rock, 
  

   with 
  occasional 
  thick 
  beds 
  of 
  red 
  clay 
  and 
  very 
  rare 
  thin, 
  discon- 
  

   tinuous 
  bands 
  and 
  nodules 
  of 
  earthy 
  limestone, 
  the 
  sandstone 
  

   itself 
  being 
  sometimes 
  calcareous, 
  and 
  thus 
  cemented 
  into 
  hard 
  

   nodular 
  masses. 
  In 
  the 
  Sirmur 
  group 
  generally 
  (below 
  the 
  

   Siwalik 
  group), 
  and 
  locally 
  in 
  the 
  Lower 
  Siwaliks, 
  the 
  sandstone 
  is 
  

   thoroughly 
  indurated 
  and 
  often 
  of 
  a 
  purple 
  tint, 
  while 
  retaining 
  

   the 
  distinctive 
  aspect. 
  In 
  the 
  Upper 
  Siwaliks 
  conglomerates 
  pre- 
  

   vail 
  largely 
  ; 
  they 
  are 
  often 
  made 
  up 
  of 
  the 
  coarsest 
  shingle, 
  pre- 
  

   cisely 
  like 
  that 
  in 
  the 
  beds 
  of 
  the 
  great 
  Himalayan 
  torrents. 
  

   Brown 
  clays 
  occur 
  often 
  with 
  the 
  conglomerate, 
  and 
  sometimes 
  

   almost 
  entirely 
  replace 
  it. 
  This 
  clay, 
  even 
  when 
  tilted 
  to 
  the 
  

   vertical, 
  is 
  undistinguishable 
  in 
  hand 
  specimens 
  from 
  that 
  of 
  the 
  

   recent 
  plains 
  deposit 
  ; 
  and 
  no 
  doubt 
  it 
  was 
  formed 
  in 
  a 
  similar 
  

   manner, 
  as 
  alluvium. 
  The 
  sandstone, 
  too, 
  of 
  this 
  zone, 
  is 
  exactly 
  

   like 
  the 
  sand 
  forming 
  the 
  banks 
  of 
  the 
  great 
  rivers, 
  but 
  in 
  a 
  more 
  

   or 
  less 
  consolidated 
  condition. 
  Thus 
  it 
  was 
  suggestive, 
  and 
  not 
  

   altogether 
  misleading, 
  to 
  say 
  that 
  the 
  Siwaliks 
  were 
  formed 
  of 
  an 
  

   upraised 
  portion 
  of 
  the 
  plains 
  of 
  India. 
  

  

  "The 
  fresh-water 
  origin 
  of 
  the 
  Siwalik 
  formation 
  seems 
  almost 
  

   as 
  indisputable 
  as 
  the 
  marine 
  origin 
  of 
  the 
  Subathu 
  beds 
  ; 
  yet, 
  

   until 
  lately 
  (1879), 
  it 
  has 
  been 
  usual 
  to 
  consider 
  the 
  Siwaliks 
  

   marine. 
  The 
  notion 
  was 
  probably 
  a 
  relic 
  of 
  the 
  opinion 
  that 
  a 
  

   water 
  basin 
  was 
  an 
  essential 
  condition 
  of 
  the 
  extensive 
  accumula- 
  

  

  