﻿GEOLOGY. 
  35 
  

  

  It 
  is 
  in 
  some 
  localities 
  banded 
  with 
  fine 
  white 
  laminae 
  or 
  with 
  bands 
  

   more 
  translucent 
  than 
  the 
  rest. 
  These 
  bands 
  run 
  parallel 
  with 
  the 
  

   bedding, 
  and 
  commonly 
  show 
  intricate 
  contortions. 
  The 
  flint 
  frac- 
  

   tures 
  conchoidally. 
  From 
  the 
  flint 
  there 
  is 
  every 
  step 
  in 
  the 
  grada- 
  

   tion 
  through 
  rocks 
  of 
  less 
  hardness 
  and 
  flinty, 
  compact 
  character 
  to 
  

   soft 
  white 
  diatomaceous 
  shale. 
  The 
  soft 
  unaltered 
  shale 
  in 
  which 
  the 
  

   constituent 
  diatom 
  tests 
  are 
  plainly 
  to 
  be 
  seen 
  occurs 
  sparingly, 
  how- 
  

   ever, 
  in 
  the 
  lower 
  division. 
  A 
  striking 
  example 
  of 
  its 
  occurrence 
  at 
  

   that 
  horizon 
  can 
  be 
  found 
  at 
  the 
  very 
  base 
  of 
  the 
  Monterey 
  on 
  the 
  

   San 
  Julian 
  ranch, 
  at 
  the 
  junction 
  of 
  El 
  Jaro 
  and 
  Salsipuedes 
  creeks, 
  

   where 
  it 
  is 
  pure, 
  soft 
  diatomaceous 
  earth 
  in 
  thick 
  beds, 
  associated 
  

   with 
  flint 
  and 
  lime 
  and 
  overlying 
  the 
  hard 
  fossiliferous, 
  calcareous 
  

   conglomerate 
  of 
  the 
  Vaqueros. 
  The 
  specimen 
  of 
  analysis 
  3 
  (p. 
  45) 
  

   is 
  from 
  this 
  point. 
  The 
  varieties 
  of 
  shale 
  are 
  very 
  numerous, 
  but 
  

   there 
  is 
  no 
  departure 
  from 
  the 
  general 
  siliceous 
  and 
  calcareous 
  types 
  

   so 
  peculiar 
  to 
  this 
  formation. 
  There 
  is 
  no 
  common 
  clay 
  shale 
  or 
  slate 
  

   derived 
  from 
  it, 
  and 
  only 
  very 
  locally 
  is 
  there 
  an 
  appearance 
  of 
  a 
  

   sandy 
  texture. 
  In 
  the 
  San 
  Rafael 
  Mountains 
  the 
  series 
  has 
  a 
  some- 
  

   what 
  different 
  character, 
  especially 
  at 
  the 
  base, 
  where 
  a 
  considerable 
  

   amount 
  of 
  sandstone, 
  in 
  some 
  places 
  soft 
  and 
  in 
  others 
  quartzitic, 
  is 
  

   interbedded 
  with 
  the 
  hard 
  calcareous 
  shales. 
  Hard, 
  coarse, 
  yellow 
  

   and 
  grayish 
  volcanic 
  tuff 
  of 
  acidic 
  nature 
  is 
  interbedded 
  with 
  the 
  Mon- 
  

   terey 
  in 
  the 
  vicinity 
  of 
  Cuyama 
  River 
  (see 
  PL 
  III, 
  A), 
  and 
  elsewhere 
  

   the 
  lowest 
  portion 
  of 
  the 
  formation 
  is 
  marked 
  by 
  beds 
  of 
  tuff 
  of 
  local 
  

   extent. 
  At 
  the 
  east 
  end 
  of 
  the 
  Santa 
  Rita 
  Hills 
  the 
  Vaqueros 
  grades 
  

   into 
  the 
  Monterey 
  through 
  beds 
  of 
  coarse 
  basic 
  tuff 
  composed 
  of 
  

   small 
  fragments 
  of 
  glass 
  and 
  crystals 
  of 
  various 
  kinds 
  and 
  of 
  large 
  

   fragments 
  of 
  pumice. 
  Round 
  bowlders 
  or 
  nodules 
  of 
  very 
  fine 
  grained 
  

   basalt 
  that 
  look 
  like 
  volcanic 
  bombs 
  are 
  included 
  in 
  this 
  tuff. 
  

  

  The 
  series 
  of 
  hard 
  shales 
  of 
  the 
  lower 
  division 
  is 
  commonly 
  impreg- 
  

   nated 
  with 
  bituminous 
  material. 
  The 
  limy 
  beds 
  have 
  almost 
  uni- 
  

   versally 
  a 
  bituminous 
  odor 
  and 
  some 
  of 
  them 
  contain 
  pockets 
  of 
  tarry 
  

   oil. 
  The 
  same 
  is 
  true 
  of 
  the 
  flint 
  with 
  the 
  difference, 
  however, 
  that 
  

   the 
  limestone 
  is 
  impregnated 
  with 
  petroleum, 
  owing 
  to 
  its 
  porosity, 
  

   whereas 
  the 
  oil 
  in 
  the 
  compact 
  flint 
  seems 
  more 
  commonly 
  to 
  be 
  con- 
  

   tained 
  along 
  lines 
  of 
  fracture 
  or 
  in 
  cavities. 
  The 
  great 
  mass 
  of 
  the 
  

   hard, 
  brittle 
  shales 
  has 
  in 
  general 
  a 
  similar 
  odor 
  or 
  is 
  discolored 
  with 
  

   oil. 
  This 
  hard 
  shale 
  series, 
  especially 
  the 
  lower 
  portion 
  of 
  it, 
  and 
  in 
  

   places 
  possibly 
  the 
  uppermost 
  sandstone 
  of 
  the 
  formation 
  just 
  below 
  

   it, 
  contains 
  the 
  principal 
  oil-bearing 
  zones 
  in 
  the 
  developed 
  fields. 
  

   The 
  fact 
  that 
  this 
  shale 
  is 
  so 
  brittle 
  and 
  fractures 
  when 
  folded 
  has 
  an 
  

   important 
  bearing 
  on 
  the 
  storing 
  of 
  oil 
  in 
  this 
  portion 
  of 
  the 
  Monterey. 
  

   The 
  fracturing 
  produces 
  cavities 
  in 
  which 
  the 
  oil 
  can 
  collect 
  while 
  

   the 
  softer 
  unf 
  ractured 
  shales 
  adj 
  acent 
  remain 
  more 
  or 
  less 
  impervious 
  

   to 
  the 
  oil. 
  

  

  