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  396 
  R. 
  E. 
  Call 
  — 
  Silicified 
  Woods 
  of 
  Eastern 
  Arkansas. 
  

  

  Slight 
  differences 
  in 
  the 
  section 
  appear 
  in 
  various 
  portions 
  

   of 
  the 
  Ridge 
  but 
  are 
  not 
  worthy 
  of 
  remark 
  in 
  this 
  connection. 
  

   The 
  generalized 
  section 
  for 
  the 
  northern 
  portion 
  of 
  the 
  Ridge, 
  

   made 
  at 
  a 
  point 
  seventy-five 
  miles 
  north 
  of 
  St. 
  Francis 
  county 
  

   shows 
  the 
  following 
  sequence 
  : 
  

  

  Generalized 
  Northern 
  Section 
  near 
  Gainesville, 
  Greene 
  County. 
  

  

  1. 
  A 
  humus, 
  largely 
  siliceous, 
  or 
  a 
  soil 
  mainly 
  sand. 
  At 
  the 
  

  

  highest 
  hilltops 
  this 
  soil 
  contains 
  gravel 
  or 
  may 
  be 
  entirely 
  

   replaced 
  by 
  waterworn 
  gravel. 
  

  

  2. 
  Gravel 
  bed, 
  commonly 
  removed 
  by 
  erosion. 
  

  

  3. 
  Sands 
  of 
  Tertiary 
  age, 
  false 
  bedded, 
  party-colored, 
  coarse 
  or 
  

  

  fine, 
  banded 
  often 
  with 
  drab, 
  red 
  or 
  white 
  pipe 
  clay, 
  or 
  the 
  

   last 
  may 
  be 
  in 
  pockets 
  or 
  lenses. 
  These 
  sands 
  are 
  generally 
  

   loose, 
  but 
  in 
  certain 
  localities 
  they 
  have 
  metamorphosed 
  into 
  

   a 
  very 
  hard, 
  glassy 
  quartzite. 
  The 
  areas 
  of 
  metamorphism 
  

   are 
  linearly 
  distributed 
  over 
  many 
  square 
  miles 
  but 
  are 
  con- 
  

   fined 
  chiefly 
  to 
  the 
  west 
  side 
  of 
  the 
  ridge. 
  Silicified 
  woods 
  

   are 
  found 
  in 
  this 
  member 
  at 
  many 
  localities, 
  but 
  none 
  has 
  

   yet 
  been 
  discovered 
  in 
  the 
  metamorphosed 
  portions. 
  

  

  4. 
  Drab, 
  blue 
  and 
  black 
  clays 
  of 
  Eocene 
  Tertiary 
  age, 
  horizon- 
  

  

  tally 
  stratified, 
  occasionally 
  fossiliferous, 
  the 
  fossils 
  being 
  

   chiefly 
  the 
  leaves 
  of 
  deciduous 
  trees. 
  These 
  clays 
  contain 
  

   rare 
  beds 
  of 
  lignite 
  of 
  small 
  extent 
  and 
  erratic 
  vertical 
  dis- 
  

   tribution. 
  Moreover, 
  the 
  clays 
  are 
  commonly 
  gypsiferous 
  

   and 
  are 
  further 
  characterized 
  by 
  abundant 
  small 
  plates 
  of 
  

   muscovite 
  in 
  the 
  cleavage 
  planes. 
  Silicified 
  wood 
  was 
  seen 
  

   at 
  a 
  single 
  locality, 
  on 
  Cache 
  River. 
  

  

  The 
  absence 
  of 
  fossils 
  in 
  nearly 
  all 
  the 
  members 
  of 
  the 
  

   Arkansas 
  Tertiary 
  renders 
  necessary 
  their 
  distinction 
  upon 
  

   lithological 
  and 
  structural 
  data. 
  The 
  large 
  masses 
  of 
  silicified 
  

   wood 
  in 
  the 
  upper 
  members 
  of 
  the 
  series 
  are 
  the 
  only 
  organic 
  

   forms 
  known 
  above 
  the 
  Eocene 
  clays. 
  If 
  in 
  any 
  way 
  these 
  

   silicified 
  woods 
  may 
  be 
  genetically 
  connected 
  with 
  the 
  lignite 
  

   beds 
  a 
  means 
  of 
  correlation 
  will 
  not 
  certainly 
  be 
  had 
  but 
  the 
  

   fact 
  may 
  sometime 
  possess 
  taxonomic 
  value. 
  Studies 
  made 
  in 
  

   eastern 
  Arkansas 
  seem 
  to 
  show 
  that 
  all 
  or 
  nearly 
  all 
  of 
  the 
  

   silicified 
  woods 
  of 
  the 
  Tertiary 
  sands 
  and 
  gravel 
  beds 
  are 
  

   derived 
  in 
  some 
  manner 
  from 
  the 
  underlying 
  beds 
  of 
  lignite. 
  

   In 
  many 
  places 
  whole 
  tree 
  trunks, 
  stumps 
  standing 
  in 
  place, 
  or 
  

   large 
  fragments 
  of 
  silicified 
  wood 
  occur 
  so 
  related 
  to 
  lignite 
  

   deposits 
  as 
  to 
  show 
  that 
  they 
  are 
  derived 
  therefrom. 
  In 
  the 
  

   northwestern 
  portion 
  of 
  Greene 
  county, 
  on 
  the 
  west 
  side 
  of 
  

   Crowley's 
  Ridge, 
  are 
  masses 
  of 
  wood 
  partly 
  in 
  the 
  form 
  of 
  lig- 
  

   nite 
  and 
  partly 
  silicified. 
  The 
  lignitized 
  part 
  is 
  buried 
  in 
  

   Eocene 
  clays 
  ; 
  the 
  silicified 
  ends 
  are 
  buried 
  in 
  Eocene 
  Tertiary 
  

   sands. 
  It 
  would 
  appear 
  that 
  in 
  this 
  case, 
  before 
  the 
  sands 
  

  

  