﻿336 
  CONTRIBUTIONS 
  TO 
  THE 
  GEOLOGY 
  OF 
  

  

  portation 
  by 
  violent 
  causes 
  from 
  a 
  distance, 
  its 
  materials 
  being 
  finely 
  

   comminuted 
  clays 
  and 
  sands 
  usually 
  arranged 
  in 
  a 
  manner 
  denoting 
  a 
  

   somewhat 
  quiet 
  deposition. 
  On 
  the 
  other 
  hand, 
  its 
  containing 
  no 
  fos- 
  

   sils, 
  its 
  distinct 
  separation 
  from 
  the 
  fossiliferous 
  marl 
  stratum 
  beneath 
  

   it, 
  the 
  surface 
  of 
  which 
  is 
  furrowed 
  and 
  deeply 
  channelled, 
  as 
  if 
  an 
  in- 
  

   terval 
  of 
  erosive 
  action 
  had 
  preceded 
  it, 
  are 
  facts 
  which 
  may 
  possibly 
  

   displace 
  it 
  from 
  the 
  Miocene 
  era 
  altogether, 
  and 
  which, 
  for 
  the 
  present 
  

   at 
  least, 
  throw 
  entire 
  uncertainty 
  upon 
  the 
  inquiry 
  as 
  to 
  the 
  position 
  

   which 
  it 
  should 
  occupy 
  in 
  the 
  Tertiary 
  series. 
  

  

  35. 
  It 
  is 
  not 
  unlikely, 
  all 
  things 
  considered, 
  that 
  the 
  origin 
  of 
  this 
  

   deposit 
  is 
  to 
  be 
  traced 
  in 
  the 
  rise 
  from 
  beneath 
  the 
  sea 
  of 
  some 
  of 
  the 
  

   more 
  western 
  portions 
  of 
  the 
  tide 
  water 
  plain 
  ; 
  in 
  other 
  words, 
  with 
  the 
  

   appearance 
  above 
  water 
  of 
  the 
  Eocene 
  tract 
  in 
  that 
  quarter. 
  This 
  is 
  

   rendered 
  probable 
  from 
  the 
  circumstance 
  that 
  this 
  superficial 
  bed 
  often 
  

   abounds 
  near 
  the 
  bottom 
  with 
  grains 
  of 
  the 
  green 
  sand 
  mineral 
  so 
  

   abundant 
  in 
  the 
  Eocene 
  of 
  Virginia. 
  It 
  is 
  corroborated, 
  likewise, 
  by 
  

   the 
  fact 
  that 
  the 
  shelly 
  Miocene 
  stratum 
  reposing 
  upon 
  the 
  Eocene, 
  

   sometimes 
  shows 
  tokens 
  of 
  considerable 
  violence 
  over 
  its 
  surface, 
  the 
  

   shells 
  being, 
  throughout 
  a 
  depth 
  of 
  several 
  feet 
  near 
  the 
  top, 
  in 
  a 
  frag- 
  

   mentary 
  state, 
  and 
  much 
  disturbed, 
  as 
  may 
  be 
  seen 
  in 
  Prince 
  George 
  

   county, 
  and 
  on 
  the 
  Chickahominy 
  river. 
  

  

  If 
  we 
  conceive 
  that 
  tracts 
  in 
  the 
  Eocene 
  district, 
  or 
  above 
  it, 
  were 
  

   upheaved 
  to 
  near 
  the 
  water's 
  level, 
  or 
  entirely 
  out 
  of 
  it, 
  while 
  the 
  

   country 
  to 
  the 
  east 
  was 
  still 
  submerged, 
  we 
  may 
  not 
  only 
  explain 
  the 
  

   facts 
  here 
  mentioned, 
  but 
  by 
  adverting 
  to 
  the 
  nature 
  of 
  the 
  actions 
  

   which 
  would 
  supervene, 
  we 
  may 
  account, 
  by 
  the 
  sudden 
  draining 
  off 
  of 
  

   the 
  uplifted 
  water, 
  for 
  the 
  eroded 
  surface 
  of 
  the 
  Miocene 
  marl, 
  and 
  the 
  

   sudden 
  and 
  total 
  extinction 
  of 
  animal 
  life 
  which 
  took 
  place. 
  To 
  this 
  

   would 
  naturally 
  succeed 
  the 
  introduction 
  of 
  nearly 
  the 
  same 
  kind 
  of 
  

   matter 
  under 
  more 
  tranquil 
  circumstances, 
  brought 
  down 
  from 
  the 
  

   newly 
  exposed 
  tract 
  by 
  river 
  action, 
  the 
  probable 
  source, 
  we 
  may 
  

   conjecture, 
  of 
  some 
  of 
  the 
  sands 
  and 
  clays 
  of 
  finer 
  texture 
  which 
  occur 
  

   so 
  regularly 
  and 
  quietly 
  stratified 
  every 
  where 
  in 
  the 
  upper 
  parts 
  of 
  

   the 
  deposit. 
  

  

  Later 
  than 
  all 
  these 
  operations 
  must 
  have 
  been 
  the 
  diluvial 
  action, 
  

   more 
  or 
  less 
  extensive, 
  which 
  grooved 
  the 
  surface 
  of 
  this 
  deposit 
  

  

  