﻿250 
  Geological 
  Survey 
  of 
  Louisiana 
  [Sect. 
  

  

  The 
  cypress 
  stump 
  stratum. 
  — 
  It 
  is 
  believed 
  that 
  the 
  cypress 
  

   stump 
  stratum 
  which 
  Hilgard 
  found 
  in 
  the 
  marshes 
  surrounding 
  

   the 
  island 
  and 
  which 
  he 
  represents 
  in 
  his 
  cross-section 
  as 
  extend- 
  

   ing 
  under 
  the 
  island,* 
  represents 
  a 
  stratum 
  much 
  ^^ounger 
  than 
  

   that 
  seen 
  at 
  Port 
  Hudson 
  bluff. 
  On 
  the 
  eastern 
  side 
  of 
  Petite 
  

   Anse 
  is 
  a 
  living 
  cj'^press 
  swamp 
  which 
  extends 
  eastward 
  along 
  

   the 
  coast 
  on 
  a 
  line 
  between 
  the 
  prairie 
  and 
  the 
  marshes. 
  Taking 
  

   the 
  present 
  rate 
  of 
  subsidence 
  on 
  the 
  Gulf 
  coast 
  (i 
  foot 
  in 
  20 
  

   years 
  according 
  to 
  the 
  observations 
  of 
  Maj. 
  Ouinnf) 
  it 
  hasn't 
  

   been 
  a 
  ver}^ 
  great 
  while 
  since 
  the 
  prairie 
  occupied 
  the 
  land 
  now 
  

   claimed 
  by 
  the 
  cypress 
  swamp 
  and 
  it 
  in 
  turn 
  occupied 
  that 
  which 
  

   is 
  now 
  sea-marsh. 
  The 
  islands 
  antedate 
  this 
  time. 
  P'urther 
  

   there 
  is 
  no 
  evidence 
  of 
  the 
  stump 
  stratum 
  in 
  any 
  of 
  the 
  borings 
  

   yet 
  made 
  on 
  the 
  islands. 
  The 
  lignite 
  has 
  in 
  every 
  case 
  been 
  

   found 
  in 
  or 
  below 
  the 
  gravel. 
  

  

  Conchisions. 
  — 
  The 
  data 
  thus 
  far 
  collected 
  seem 
  to 
  show 
  that 
  the 
  

   salt 
  mass 
  on 
  Petite 
  Anse 
  represents 
  the 
  edge 
  of 
  an 
  upturned 
  

   fault 
  block. 
  The 
  dip 
  together 
  with 
  the 
  absence 
  of 
  the 
  impure 
  

   salt 
  bed 
  seen 
  on 
  the 
  top 
  of 
  the 
  Belle 
  Isle 
  anticline 
  would 
  seem 
  to 
  

   indicate 
  this. 
  Whether 
  this 
  be 
  due 
  to 
  orographic 
  movements 
  or 
  

   to 
  faults 
  produced 
  b}' 
  the 
  dissolution 
  of 
  vast 
  amounts 
  of 
  the 
  

   underlying 
  salt 
  cannot 
  be 
  positivel}^ 
  stated, 
  but 
  the 
  evidence 
  at 
  

   hand 
  rather 
  favors 
  the 
  former. 
  The 
  dip 
  of 
  the 
  lignite 
  bed, 
  the 
  

   only 
  surface 
  bed 
  whose 
  dip 
  could 
  be 
  determined, 
  taken 
  in 
  con- 
  

   nection 
  with 
  the 
  data 
  furnished 
  by 
  the 
  holes 
  drilled 
  near 
  it 
  indi- 
  

   cates 
  that 
  this 
  bed 
  rests 
  unconformably 
  on 
  the 
  salt. 
  Two 
  

   separate 
  movements 
  of 
  the 
  strata 
  are 
  then 
  indicated 
  : 
  an 
  initial 
  

   movement 
  of 
  about 
  38°, 
  with 
  an 
  interval 
  during 
  which 
  the 
  cla}^ 
  

   and 
  lignite 
  and 
  the 
  pink 
  sand 
  bed 
  were 
  deposited 
  around 
  the 
  

  

  *See 
  section 
  of 
  island. 
  Hilgard, 
  Smith. 
  Contr. 
  vol. 
  23, 
  separate 
  No. 
  248, 
  

   1872. 
  

  

  Copied 
  by 
  Pomeroy, 
  Eng. 
  and 
  Min. 
  Jour., 
  vol. 
  46, 
  pp. 
  280-281, 
  1888. 
  Sci. 
  

   Am.,Suppl., 
  vol. 
  26, 
  pp. 
  10719-10720, 
  No. 
  671, 
  1888; 
  Am. 
  Inst. 
  Mining 
  Kng. 
  

   Trans., 
  vol. 
  17, 
  pp. 
  107-113, 
  1889. 
  

  

  In 
  this 
  connection 
  it 
  is 
  well 
  to 
  call 
  attention 
  to 
  the 
  difference 
  between 
  

   this 
  section 
  and 
  the 
  facts 
  as 
  they 
  now 
  present 
  themselves. 
  

  

  \ 
  An. 
  Rept. 
  U. 
  S. 
  Engineer 
  1895. 
  Quoted 
  in 
  Appleton's 
  Annual 
  Cyclo- 
  

   paedia, 
  1895, 
  New 
  York 
  1896. 
  

  

  