﻿Ill] 
  The 
  Fire 
  Isi^ands 
  : 
  Origin 
  259 
  

  

  This 
  section 
  is 
  quite 
  different 
  from 
  the 
  other 
  sections. 
  The 
  

   uncertainty 
  of 
  its 
  location 
  makes 
  it 
  difficult 
  to 
  frame 
  any 
  conclu- 
  

   sions 
  regarding 
  it. 
  It 
  may 
  represent 
  a 
  local 
  gravel 
  bed 
  in 
  the 
  

   Port 
  Hudson 
  or 
  a 
  slight 
  uplift 
  connected 
  with 
  the 
  insular 
  uplifts. 
  

   If 
  the 
  latter 
  be 
  the 
  case 
  a 
  deep 
  well 
  will 
  probably 
  reach 
  salt. 
  

  

  General 
  Considerations 
  

   The 
  Origin 
  of 
  the 
  Islands 
  

  

  Method 
  and 
  date 
  of 
  formation. 
  — 
  Onh' 
  two 
  of 
  the 
  islands 
  furnish 
  

   definite 
  data 
  on 
  the 
  method 
  and 
  date 
  of 
  their 
  formation. 
  Belle 
  

   Isle 
  shows 
  a 
  very 
  distinct 
  dome-shaped 
  fold. 
  Petite 
  Anse 
  seems 
  

   to 
  represent 
  a 
  fault 
  block. 
  

  

  They 
  cannot 
  be 
  regarded 
  as 
  a 
  portion 
  of 
  a 
  great 
  anticlinal 
  

   ridge 
  or 
  backbone, 
  as 
  Hilgard 
  supposed, 
  extending 
  from 
  north- 
  

   west 
  to 
  southeast. 
  On 
  Petite 
  Anse 
  the 
  line 
  of 
  strike 
  of 
  the 
  lig- 
  

   nite, 
  sandstone 
  and 
  salt 
  is 
  at 
  right 
  angles 
  to 
  the 
  line 
  of 
  the 
  islands, 
  

   i. 
  e., 
  across 
  the 
  supposed 
  fold 
  rather 
  than 
  with 
  it. 
  On 
  Belle 
  

   Isle 
  the 
  main 
  line 
  of 
  hills 
  and 
  the 
  salt 
  mass 
  lie 
  northeast 
  and 
  

   southwest 
  instead 
  of 
  northwest 
  and 
  southeast. 
  On 
  Grande 
  Cote 
  

   the 
  main 
  line 
  of 
  hills 
  and 
  the 
  salt 
  mass 
  extend 
  almost 
  north 
  and 
  

   south; 
  

  

  No 
  evidence 
  of 
  the 
  two 
  movements 
  indicated 
  on 
  Petite 
  Anse 
  has 
  

   been 
  seen 
  on 
  the 
  other 
  islands 
  and 
  it 
  maj' 
  be 
  that 
  the 
  phenomenon 
  

   there 
  shown 
  is 
  the 
  result 
  of 
  complex 
  faulting. 
  If 
  we 
  suppose 
  

   the 
  Five 
  Islands 
  were 
  made 
  at 
  the 
  same 
  time, 
  the 
  time 
  of 
  this 
  

   crustal 
  movement 
  can 
  be 
  approximated 
  very 
  closely. 
  The 
  prin- 
  

   cipal 
  folding 
  or 
  faulting 
  occurred 
  after 
  the 
  deposition 
  of 
  the 
  shell 
  

   bed 
  on 
  Belle 
  Isle 
  and 
  before 
  the 
  bone 
  bed 
  on 
  Petite 
  Anse. 
  Both 
  

   of 
  these 
  are 
  Pleistocene. 
  

  

  The 
  upper 
  clay 
  beds 
  spread 
  mantlewise 
  over 
  the 
  gravel 
  beds, 
  

   on 
  Grande 
  Cote, 
  Cote 
  Blanche 
  and 
  Cote 
  Carline, 
  seem 
  to 
  have 
  

   been 
  deposited 
  after 
  the 
  formation 
  of 
  the 
  islands 
  ; 
  very 
  probably 
  

   at 
  the 
  same 
  time 
  and 
  in 
  the 
  same 
  manner 
  as 
  the 
  Icess 
  beds 
  of 
  the 
  

   eastern 
  escarpment 
  of 
  the 
  Mississippi 
  valley. 
  

  

  It 
  would 
  seem 
  then 
  that 
  the 
  formation 
  of 
  the 
  islands 
  began 
  

   with 
  a 
  possible 
  initial 
  movement 
  (evidences 
  of 
  which 
  have 
  thus 
  

   far 
  been 
  seen 
  only 
  on 
  Petite 
  Anse) 
  in 
  probably 
  late 
  Tertiary 
  

  

  