﻿136 
  S. 
  Powers 
  — 
  The 
  Butler 
  Salt 
  Borne. 
  

  

  of 
  Midway 
  age. 
  Limestone 
  is 
  exposed 
  on 
  the 
  east 
  side 
  

   of 
  the 
  Steen 
  salt 
  dome, 
  in 
  the 
  northern 
  portion 
  of 
  Smith 
  

   County, 
  but 
  it 
  is 
  unfossiliferous. 
  It 
  has 
  been 
  considered 
  

   to 
  be 
  of 
  Midway 
  age. 
  

  

  Near 
  the 
  junction 
  of 
  the 
  Bonner's 
  Ferry 
  and 
  Oakwood 
  

   roads 
  plastic 
  shale 
  of 
  yellow 
  to 
  brown 
  color 
  with 
  only 
  one 
  

   ferruginous 
  layer 
  is 
  exposed 
  in 
  a 
  gully. 
  The 
  Upper 
  

   Cretaceous 
  fossils 
  were 
  collected 
  near 
  the 
  head 
  of 
  the 
  

   gully, 
  or 
  about 
  300 
  to 
  400 
  feet 
  stratigraphically 
  below 
  the 
  

   shales 
  in 
  which 
  fossils 
  of 
  Eocene 
  age 
  were 
  found. 
  Judg- 
  

   ing 
  from 
  the 
  stratigraphy, 
  the 
  Cretaceous 
  shales 
  belong 
  

   to 
  the 
  Navarro 
  formation. 
  This 
  exposure 
  represents 
  the 
  

   lowest 
  horizon 
  exposed 
  in 
  the 
  dome. 
  

  

  Structure. 
  

  

  Nothing 
  is 
  known 
  of 
  the 
  underground 
  conditions 
  at 
  the 
  

   dome 
  except 
  that 
  salt 
  was 
  found 
  beneath 
  the 
  center 
  at 
  a 
  

   few 
  hundred 
  feet 
  and 
  that 
  the 
  rocks 
  dip 
  quaquaversally 
  

   from 
  the 
  center. 
  The 
  shape 
  of 
  the 
  central 
  salt 
  core 
  is 
  

   unknown, 
  but 
  is 
  believed 
  to 
  be 
  circular 
  as 
  indicated 
  on 
  

   the 
  map, 
  and 
  6000 
  feet 
  in 
  diameter. 
  The 
  diameter 
  of 
  the 
  

   area 
  underlain 
  by 
  tilted 
  rocks 
  surrounding 
  the 
  core 
  is 
  

   about 
  2y 
  2 
  miles. 
  Exploration 
  for 
  salt 
  in 
  other 
  salt 
  

   domes 
  has 
  shown 
  that 
  the 
  upper 
  surface 
  of 
  the 
  salt 
  body 
  

   is 
  very 
  irregular 
  and 
  has 
  no 
  relation 
  to 
  the 
  configuration 
  

   of 
  the 
  surface 
  of 
  the 
  ground. 
  

  

  The 
  thickness 
  of 
  formations 
  on 
  the 
  outcrop 
  may 
  be 
  

   roughly 
  estimated 
  and 
  compared 
  with 
  data 
  from 
  well 
  

   logs. 
  The 
  line 
  between 
  the 
  Mount 
  Selman 
  and 
  Wilcox 
  

   formations 
  can 
  be 
  drawn 
  in 
  the 
  field 
  in 
  a 
  general 
  way 
  

   from 
  the 
  topography 
  — 
  the 
  former 
  caps 
  hills 
  of 
  noticeable 
  

   relief 
  forming 
  a 
  "wold." 
  The 
  Wilcox-Midway 
  contact 
  

   is 
  supposed 
  to 
  be 
  marked 
  by 
  a 
  change 
  from 
  shale 
  below 
  

   to 
  sandy 
  shale 
  and 
  sand 
  above, 
  but 
  this 
  contact 
  is 
  con- 
  

   cealed 
  in 
  Burton 
  Hollow. 
  The 
  Midway-Navarro 
  contact 
  

   is 
  lithologically 
  indefinite. 
  

  

  In 
  well 
  logs 
  from 
  the 
  Red 
  River 
  and 
  Crichton 
  fields, 
  in 
  

   Louisiana, 
  it 
  may 
  be 
  noticed 
  that 
  the 
  Annona 
  chalk 
  and 
  

   Nacatoch 
  sand 
  are 
  overlain 
  by 
  shale 
  and 
  gumbo 
  which 
  ex- 
  

   tend 
  to 
  the 
  surface 
  giving 
  a 
  thickness 
  of 
  900 
  feet 
  or 
  less. 
  

   The 
  Wilcox 
  formation 
  everywhere 
  covers 
  the 
  surface. 
  

   Southwest 
  of 
  the 
  Sabine 
  uplift 
  the 
  thickness 
  of 
  this 
  

   gumbo 
  increases 
  to 
  1330 
  feet 
  in 
  Shelby 
  County 
  and 
  to 
  

  

  