﻿96 
  Geological 
  Survey 
  of 
  Louisiana 
  [Sect. 
  

  

  sandstone 
  as 
  exposed 
  at 
  Grand 
  Gulf 
  Mississippi. 
  Hilgard 
  gives 
  

   the 
  following 
  description 
  of 
  it 
  : 
  " 
  The 
  typical 
  Grand 
  Gulf 
  

   sandstone 
  consists 
  of 
  grains 
  of 
  pellucid 
  quartz, 
  constituting 
  a 
  

   rather 
  coarse 
  sand, 
  imbeded 
  in 
  an 
  opaque, 
  white, 
  enamel-like 
  

   mass 
  of 
  silex, 
  which 
  forms 
  quite 
  half 
  the 
  bulk 
  of 
  the 
  rock." 
  

  

  In 
  the 
  southern 
  part 
  of 
  the 
  territory 
  occupied 
  by 
  this 
  

   formation 
  (possibly, 
  in 
  the 
  part 
  belonging 
  to 
  the 
  Pascagoula 
  

   formation) 
  sandy 
  clays 
  and 
  pure 
  highly 
  tenaceous 
  massive 
  clays 
  

   of 
  a 
  gray, 
  grayish-white, 
  blue 
  or 
  green 
  color 
  are 
  the 
  rule. 
  The 
  

   color 
  in 
  the 
  blue 
  and 
  green 
  clays 
  is 
  often 
  very 
  intense, 
  though 
  

   on 
  the 
  surface 
  they 
  often 
  appear 
  yellow 
  from 
  oxidation. 
  In 
  

   some 
  cases 
  black 
  lignitic 
  clays 
  are 
  found 
  in 
  this 
  deposit. 
  Some 
  

   of 
  the 
  beds 
  are 
  very 
  calcareous 
  and 
  produce 
  small 
  black 
  land 
  

   prairies. 
  In 
  the 
  northern 
  part 
  of 
  the 
  formation 
  there 
  are 
  

   occasional 
  beds 
  of 
  very 
  fine 
  white 
  clay, 
  locally 
  called 
  "chalk." 
  

  

  The 
  sandstones 
  have 
  resisted 
  erosion 
  much 
  better 
  than 
  the 
  

   underlying 
  Jackson 
  and 
  Vicksburg 
  beds. 
  This 
  has 
  given 
  raise 
  

   to 
  a 
  somewhat 
  level 
  Jackson 
  plain 
  bordered 
  on 
  the 
  south 
  by 
  a 
  

   high, 
  rugged 
  line 
  of 
  hills. 
  This 
  very 
  abrupt 
  northern 
  declivity 
  

   is 
  in 
  sharp 
  contrast 
  to 
  the 
  gradual 
  southern 
  slope 
  which 
  carries 
  

   the 
  formation 
  down 
  to 
  the 
  level 
  of 
  the 
  southern 
  prairies. 
  

  

  Distribution. 
  — 
  Large 
  outcrops 
  of 
  Grand 
  Gulf 
  sandstone 
  are 
  to 
  

   be 
  seen 
  at 
  Harrisonburg 
  and 
  Sicily 
  island. 
  On 
  the 
  divide 
  

   between 
  the 
  Ouachita 
  and 
  Little 
  river 
  the 
  Grand 
  Gulf 
  extends 
  

   well 
  to 
  the 
  north, 
  reaching 
  a 
  point 
  near 
  Rosefield. 
  Along 
  the 
  

   edge 
  of 
  the 
  formation 
  "chalk" 
  or 
  fine 
  white 
  clay 
  has 
  been 
  

   reported 
  in 
  a 
  number 
  of 
  places. 
  From 
  Rosefield, 
  according 
  to 
  

   Hopkins, 
  the 
  northern 
  line 
  of 
  the 
  Grand 
  Gulf 
  follows 
  the 
  Bayou 
  

   Funne 
  Louis 
  to 
  Centerville, 
  then 
  turns 
  west 
  and 
  crosses 
  Little 
  

   river 
  a 
  little 
  below 
  Gilmore's 
  ferry. 
  On 
  the 
  Colfax- 
  Winnfield 
  

   road 
  the 
  high 
  Grand 
  Gulf 
  hills 
  are 
  encountered 
  just 
  south 
  of 
  

   Saddle 
  bayou. 
  About 
  two 
  miles 
  northwest 
  of 
  Colfax 
  there 
  is 
  a 
  

   very 
  good 
  outcrop 
  of 
  Grand 
  Gulf 
  sandstone 
  in 
  Rocky 
  ford. 
  

   The 
  sandstone 
  is 
  quite 
  abundant 
  as 
  far 
  north 
  as 
  Sec. 
  19, 
  7 
  N., 
  

   3 
  W. 
  Around 
  Lena 
  are 
  large 
  quarries 
  in 
  the 
  Grand 
  Gulf 
  rocks. 
  

   Hilgard 
  reports 
  these 
  beds 
  as 
  capping 
  the 
  elevated 
  ridges 
  

   about 
  Cloutierville 
  on 
  Red 
  river.* 
  The 
  next 
  notable 
  exposure 
  

  

  *Am. 
  Jour. 
  Sci.. 
  2d 
  Series, 
  vol. 
  48, 
  1869, 
  p. 
  337. 
  

  

  