﻿50 
  SANTA 
  MARIA 
  OIL 
  DISTRICT, 
  CALIFORNIA. 
  

  

  to 
  1,040 
  feei 
  below 
  the 
  surface 
  in 
  Hill 
  well 
  No. 
  l,in 
  the 
  Lonipoc 
  field, 
  

   which 
  are 
  Identical 
  iii 
  appearance 
  and 
  texture 
  ■with 
  the 
  burnt 
  shale 
  

   elsewhere. 
  Traces 
  of 
  petroleum 
  were 
  associated 
  with 
  the 
  upper 
  

   stratum 
  of 
  burnt 
  shale 
  in 
  this 
  well. 
  In 
  numerous 
  other 
  wells 
  in 
  the 
  

   Santa 
  Maria 
  field 
  red 
  shale, 
  doubtless 
  burnt, 
  was 
  found 
  at 
  depths 
  

   ranging 
  between 
  90 
  and 
  330 
  feet 
  below 
  the 
  surface. 
  The 
  hardening 
  

   consequent 
  on 
  the 
  burning 
  has 
  in 
  some 
  places 
  rendered 
  the 
  rock 
  dif- 
  

   ficult 
  to 
  pierce 
  with 
  the 
  drill. 
  

  

  LITHOLOGIC 
  CHARACTER 
  OF 
  BURNT 
  SHALE. 
  

  

  The 
  burnt 
  shale 
  exhibits 
  all 
  stages 
  of 
  change 
  from 
  a 
  slight 
  indura- 
  

   tion 
  and 
  discoloration, 
  due, 
  probably, 
  to 
  oxidation 
  of 
  iron, 
  to 
  an 
  

   extreme 
  hardening 
  and 
  partial 
  fusion. 
  Where 
  slightly 
  altered, 
  the 
  

   normal 
  white 
  shale 
  assumes 
  a 
  light-pink 
  color. 
  From 
  this 
  stage 
  it 
  

   passes 
  through 
  various 
  shades 
  of 
  rose 
  and 
  brick-red 
  and 
  deepens 
  in 
  

   color 
  to 
  a 
  reddish, 
  bluish, 
  or 
  greenish 
  black, 
  or 
  even 
  a 
  true 
  black. 
  In 
  

   the 
  advanced 
  stages 
  of 
  change 
  it 
  becomes 
  a 
  rough, 
  brittle, 
  reddish, 
  

   porous 
  slag, 
  like 
  vesicular 
  lava, 
  or 
  a 
  very 
  hard, 
  compact, 
  dark, 
  and 
  

   dull-colored 
  rock, 
  looking 
  something 
  like 
  a 
  compact 
  igneous 
  rock. 
  

   An 
  example 
  of 
  partly 
  vesicular 
  and 
  partly 
  compact 
  burnt 
  shale 
  is 
  

   shown 
  in 
  PI. 
  V, 
  B 
  (p. 
  36). 
  Burnt 
  shale 
  is 
  not 
  crystalline, 
  but 
  the 
  

   texture 
  is 
  so 
  variable 
  as 
  to 
  give 
  a 
  patchy 
  appearance 
  to 
  surfaces. 
  In 
  

   one 
  place 
  it 
  may 
  be 
  compact 
  and 
  black, 
  nearly 
  full 
  of 
  irregular 
  cavi- 
  

   ties,- 
  surrounded 
  by 
  patches 
  of 
  different 
  colors; 
  in 
  another, 
  vesicular 
  

   and 
  reddish. 
  Whereas 
  the 
  weight 
  of 
  the 
  original 
  shale 
  is 
  slight, 
  the 
  

   lighter 
  varieties 
  having 
  a 
  specific 
  gravity 
  less 
  than 
  that 
  of 
  water, 
  the 
  

   excessively 
  burnt 
  shale 
  is 
  very 
  heavy. 
  The 
  material 
  has 
  evidently 
  

   contracted 
  to 
  much 
  less 
  than 
  its 
  original 
  volume, 
  the 
  angular 
  cavities 
  

   and 
  irregular 
  vesicles 
  being 
  one 
  consequence 
  of 
  this 
  contraction. 
  

  

  Under 
  the 
  microscope 
  the 
  rock 
  in 
  the 
  more 
  advanced 
  stages 
  of 
  alter- 
  

   ation 
  appears 
  to 
  have 
  an 
  exceedingly 
  fine 
  grained, 
  amorphous, 
  porous 
  

   groundmass, 
  discolored 
  with 
  reddish-brown 
  or 
  gray 
  stains. 
  Black 
  

   filaments 
  and 
  dots 
  appearing 
  like 
  carbonaceous 
  material 
  are 
  common. 
  

   Exceedingly 
  minute 
  rounded 
  and 
  irregular 
  grains 
  scattered 
  through 
  

   the 
  whole, 
  but 
  forming 
  no 
  appreciable 
  proportion 
  of 
  it, 
  are 
  the 
  only 
  

   portions 
  visible 
  under 
  crossed 
  nicols. 
  They 
  extinguish 
  four 
  times 
  in 
  

   a 
  revolution 
  of 
  the 
  field 
  and 
  are 
  probably 
  clastic 
  quartz 
  grains. 
  

   These 
  are 
  characteristic 
  of 
  the 
  unaltered 
  shale 
  as 
  well. 
  

  

  G. 
  II. 
  Eldridge° 
  notes 
  an 
  occurrence 
  of 
  burnt 
  shale 
  near 
  the 
  old 
  

   Blake 
  asphalt 
  mine, 
  south 
  of 
  Graciosa 
  Ridge. 
  He 
  says: 
  "The 
  shale 
  

   now 
  appears 
  red, 
  ashlike 
  to 
  hard 
  and 
  clinker-like, 
  glazed, 
  or 
  silicified; 
  

   bodies 
  of 
  bitumen 
  contained 
  within 
  this 
  have 
  the 
  appearance 
  of 
  a 
  

   coke, 
  as 
  though 
  derived 
  from 
  the 
  solid 
  fixed 
  carbon 
  of 
  the 
  petroleum." 
  

  

  a 
  The 
  asphalt 
  and 
  bituminous 
  rock 
  deposits 
  of 
  the 
  United 
  States: 
  Twenty-second 
  Ann. 
  Rept. 
  

   U. 
  S. 
  C.eol. 
  Survey, 
  pt. 
  1, 
  1901, 
  p. 
  428. 
  

  

  