﻿PETROLEUM 
  GEOLOGY 
  — 
  HEROY 
  187 
  

  

  The 
  most 
  important 
  area 
  in 
  which 
  petroleum 
  has 
  accumulated 
  in 
  

   relation 
  to 
  salt 
  plugs 
  is 
  in 
  Louisiana 
  and 
  Texas, 
  near 
  the 
  coast 
  of 
  the 
  

   Gulf 
  of 
  Mexico. 
  The 
  discovery 
  of 
  the 
  Spindletop 
  field, 
  Texas, 
  in 
  1901 
  

   originated 
  a 
  campaign 
  of 
  exploration 
  which 
  has 
  resulted 
  in 
  the 
  devel- 
  

   opment 
  of 
  over 
  200 
  oil-bearing 
  structures, 
  of 
  which 
  over 
  100 
  are 
  defi- 
  

   nitely 
  known 
  to 
  be 
  salt 
  domes, 
  while 
  most 
  of 
  the 
  others, 
  from 
  struc- 
  

   tural 
  and 
  other 
  evidence, 
  are 
  believed 
  to 
  overlie 
  deep-seated 
  salt 
  plugs 
  

   (Barton 
  and 
  Sawtelle, 
  1936). 
  Salt 
  domes 
  are 
  important 
  types 
  of 
  

   accumulation 
  in 
  Mexico, 
  Germany, 
  Rumania, 
  Arabia, 
  Transcaspia, 
  

   and 
  Iran. 
  

  

  Igneous 
  intrusions 
  have 
  caused 
  the 
  deformation 
  of 
  sediments 
  and 
  

   thus 
  produced 
  traps. 
  Well-established 
  examples 
  of 
  this 
  type 
  of 
  ac- 
  

   cumulation 
  are 
  the 
  Thrall 
  (Udden 
  and 
  Bybee, 
  1916), 
  Chapman 
  (Sell- 
  

   ards, 
  1932), 
  and 
  Lytton 
  Springs 
  (Collingwood 
  and 
  Rettger, 
  1926) 
  

   fields 
  in 
  Texas, 
  the 
  Furbero 
  field 
  in 
  Mexico 
  (DeGolyer, 
  1932), 
  and, 
  

   probably, 
  the 
  Motembo 
  field 
  of 
  Cuba 
  (Lewis, 
  1932). 
  

  

  Combination 
  traps. 
  — 
  Many 
  oil 
  fields 
  are 
  more 
  complex 
  in 
  character 
  

   than 
  those 
  which 
  have 
  been 
  cited. 
  Among 
  larger 
  fields 
  Bradford, 
  

   Pennsylvania, 
  is 
  an 
  example 
  of 
  a 
  trap 
  formed 
  by 
  a 
  combination 
  of 
  de- 
  

   positiohal 
  and 
  deformational 
  factors. 
  Structurally 
  the 
  field 
  is 
  anti- 
  

   clinal 
  and 
  has 
  a 
  gas 
  cap 
  and 
  a 
  marginal 
  oil-water 
  contact, 
  but 
  the 
  

   lensing 
  out 
  of 
  the 
  principal 
  reservoir 
  sand 
  within 
  part 
  of 
  the 
  area 
  of 
  

   closure 
  has 
  limited 
  commercial 
  production 
  to 
  only 
  part 
  of 
  the 
  structure 
  

   (Fettke, 
  1938). 
  In 
  Cushing, 
  Oklahoma, 
  and 
  other 
  mid-continent 
  

   fields, 
  folding, 
  faulting, 
  and 
  overlap 
  all 
  occur 
  and 
  to 
  some 
  degree 
  have 
  

   influenced 
  the 
  accumulation 
  of 
  oil 
  and 
  gas. 
  Nienhagen, 
  in 
  Germany, 
  

   Boryslaw, 
  in 
  Poland, 
  and 
  Bustenari, 
  in 
  Rumania, 
  are 
  European 
  ex- 
  

   amples 
  of 
  complex 
  structures. 
  Many 
  other 
  fields 
  throughout 
  the 
  world 
  

   could 
  be 
  mentioned 
  as 
  examples 
  of 
  involved 
  conditions 
  of 
  accumula- 
  

   tion 
  but, 
  to 
  the 
  extent 
  that 
  the 
  facts 
  have 
  been 
  ascertained, 
  it 
  has 
  been 
  

   found 
  that 
  the 
  fundamental 
  principal 
  of 
  buoyancy 
  may 
  be 
  universally 
  

   applied. 
  

  

  TIME 
  OF 
  ACCUMULATION 
  

  

  The 
  sedimentary 
  rocks 
  in 
  which 
  petroleum 
  has 
  originated 
  were 
  de- 
  

   posited 
  in 
  submerged 
  areas 
  in 
  the 
  earlier 
  phase 
  of 
  an 
  orogenic 
  cycle. 
  

   The 
  volume 
  of 
  sediment 
  which 
  may 
  be 
  deposited 
  in 
  a 
  single 
  cycle 
  in 
  

   an 
  area 
  undergoing 
  depression 
  may 
  reach 
  enormous 
  proportions. 
  

   In 
  the 
  Rocky 
  Mountain 
  region 
  over 
  10,000 
  feet 
  of 
  Upper 
  Cretaceous 
  

   sediments 
  were 
  deposited 
  (Spieker, 
  1931), 
  and 
  in 
  the 
  Gulf 
  Coast 
  

   geosyncline 
  the 
  maximum 
  thickness 
  may 
  be 
  greater 
  than 
  30,000 
  feet 
  

   (Barton, 
  Ritz, 
  and 
  Hickey, 
  1933). 
  This 
  earlier 
  phase 
  is 
  one 
  of 
  quiet 
  

   sinking 
  (Bucher, 
  1933, 
  p. 
  126), 
  accompanied 
  by 
  compaction, 
  and 
  the 
  

   sediments 
  may 
  be 
  undisturbed 
  by 
  major 
  diastrophic 
  movements 
  for 
  

   many 
  millions 
  of 
  year 
  after 
  deposition 
  (Levorsen, 
  1935). 
  The 
  later 
  

  

  