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  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1943 
  

  

  phase 
  of 
  the 
  orogenic 
  cycle 
  is 
  one 
  of 
  crustal 
  folding, 
  during 
  which 
  

   ranges 
  are 
  formed 
  that 
  divide 
  the 
  original 
  submergent 
  area 
  into 
  sepa- 
  

   rate 
  basins. 
  Additional 
  materials 
  are 
  removed 
  from 
  the 
  uprising 
  

   ranges 
  to 
  add 
  to 
  the 
  volume 
  of 
  sediment 
  in 
  these 
  basins. 
  Local 
  folding 
  

   and 
  progressive 
  overlap 
  will, 
  during 
  this 
  phase, 
  form 
  traps 
  along 
  the 
  

   margins 
  of 
  the 
  basins 
  and 
  the 
  flanks 
  of 
  the 
  uplifts 
  (Herold, 
  1938, 
  

   p. 
  837). 
  

  

  The 
  generalized 
  history 
  just 
  outlined 
  is 
  typical 
  of 
  some 
  areas 
  which 
  

   have 
  undergone 
  a 
  single 
  orogenic 
  cycle. 
  Most 
  basins 
  have 
  had 
  more 
  

   complex 
  histories; 
  breaks 
  in 
  deposition 
  are 
  marked 
  by 
  unconformi- 
  

   ties, 
  and 
  folding 
  may 
  have 
  occurred 
  at 
  more 
  than 
  one 
  period. 
  The 
  

   petroleum 
  generated 
  and 
  retained 
  in 
  the 
  sediments, 
  equally 
  with 
  

   them, 
  has 
  been 
  affected 
  by 
  all 
  the 
  forces 
  exerted 
  during 
  the 
  orogenic 
  

   cycle. 
  In 
  contrast, 
  petroleum 
  is 
  capable 
  of 
  movement, 
  and 
  its 
  loca- 
  

   tion 
  has 
  shifted 
  as 
  a 
  result 
  of 
  changes 
  in 
  the 
  attitude 
  of 
  the 
  containing 
  

   sediments. 
  Each 
  successive 
  orogenic 
  cycle, 
  therefore, 
  may 
  influence 
  

   the 
  accumulation 
  of 
  petroleum 
  and 
  the 
  location 
  of 
  petroleum 
  deposits. 
  

  

  Movement 
  of 
  petroleum 
  during 
  the 
  earlier 
  phase 
  of 
  an 
  orogenic 
  

   cycle 
  is 
  controlled 
  primarily 
  by 
  the 
  regional 
  dip 
  due 
  to 
  subsidence, 
  

   and 
  such 
  movement, 
  conceivably, 
  can 
  occur 
  quite 
  early 
  in 
  the 
  history 
  

   of 
  the 
  sediments. 
  At 
  the 
  close 
  of 
  the 
  first 
  phase, 
  the 
  quiet 
  sinking 
  

   period, 
  petroleum 
  should 
  have 
  been 
  concentrated 
  toward 
  the 
  more 
  

   elevated 
  portion 
  of 
  the 
  area 
  of 
  deposition 
  insofar 
  as 
  the 
  continuity 
  

   of 
  carrier 
  beds 
  would 
  permit. 
  During 
  the 
  second 
  phase, 
  the 
  period 
  

   of 
  crustal 
  folding, 
  local 
  traps 
  are 
  formed 
  into 
  which 
  the 
  petroleum 
  

   migrates 
  and 
  accumulates. 
  Levorsen 
  (1935) 
  has 
  pointed 
  out 
  that 
  

   those 
  local 
  traps 
  which 
  form 
  in 
  the 
  area 
  of 
  primary 
  regional 
  accumu- 
  

   lation 
  tend 
  to 
  be 
  more 
  productive 
  than 
  similar 
  traps 
  outside 
  such 
  

   areas. 
  

  

  In 
  areas 
  which 
  have 
  been 
  affected 
  by 
  more 
  than 
  one 
  period 
  of 
  

   orogenic 
  movement 
  some 
  traps 
  formed 
  during 
  earlier 
  cycles 
  have 
  

   survived 
  through 
  later 
  cycles 
  while 
  others 
  have 
  been 
  destroyed. 
  The 
  

   traps 
  that 
  lie 
  in 
  the 
  deeper 
  parts 
  of 
  the 
  basins 
  have 
  the 
  better 
  chance 
  

   of 
  survival. 
  In 
  some 
  cases 
  oil 
  has 
  migrated 
  from 
  rocks 
  which 
  were 
  

   formed 
  during 
  the 
  earlier 
  cycle 
  into 
  those 
  which 
  were 
  formed 
  during 
  

   a 
  succeeding 
  one; 
  traps 
  in 
  basal 
  sands 
  above 
  an 
  unconformity 
  have 
  

   been 
  filled 
  with 
  oil 
  which 
  has 
  moved 
  upward 
  from 
  older 
  deposits 
  

   below 
  the 
  unconformity. 
  

  

  Traps 
  which 
  are 
  formed 
  during 
  earlier 
  cycles 
  of 
  orogeny 
  or 
  during 
  

   earlier 
  periods 
  of 
  folding 
  have 
  an 
  advantage 
  over 
  those 
  which 
  are 
  

   formed 
  later 
  in 
  the 
  history 
  of 
  a 
  basin. 
  The 
  Kelsey 
  anticline, 
  Texas, 
  

   is 
  an 
  illustration 
  of 
  a 
  well-closed 
  but 
  barren 
  trap 
  which 
  is 
  thought 
  

   to 
  have 
  been 
  formed 
  too 
  late 
  to 
  accumulate 
  oil 
  in 
  the 
  Woodbine 
  sand, 
  

   which 
  is 
  so 
  productive 
  in 
  other 
  neighboring 
  fields 
  in 
  the 
  East 
  Texas 
  

  

  