﻿GEOLOGY. 
  47 
  

  

  rial 
  might 
  have 
  been, 
  and 
  the 
  more 
  or 
  less 
  completely 
  crystalline 
  

   character 
  of 
  the 
  harder 
  shales 
  shows 
  that 
  metamorphism 
  has 
  taken 
  

   place. 
  The 
  most 
  plausible 
  theory, 
  therefore, 
  is 
  that 
  the 
  Monterey 
  

   shale 
  as 
  originally 
  laid 
  down 
  was 
  fairly 
  constant 
  in 
  character 
  and 
  

   that 
  it 
  has 
  undergone 
  alteration 
  extensively, 
  as 
  well 
  as 
  very 
  locally, 
  

   through 
  the 
  agency 
  of 
  siliceous 
  waters, 
  the 
  older 
  portions 
  of 
  the 
  

   formation, 
  and 
  possibly 
  the 
  more 
  disturbed 
  portions, 
  having 
  been 
  

   most 
  generally 
  subjected 
  to 
  the 
  change. 
  The 
  limestone 
  has 
  in 
  

   places 
  been 
  altered 
  after 
  a 
  fashion 
  somewhat 
  similar 
  to 
  that 
  of 
  the 
  

   siliceous 
  shales, 
  being 
  changed 
  to 
  marble, 
  probably 
  as 
  the 
  result 
  of 
  

   solution 
  and 
  redeposition. 
  

  

  The 
  Monterey 
  rocks 
  likewise 
  show 
  the 
  result 
  of 
  contact 
  metamor- 
  

   phism 
  to 
  a 
  very 
  local 
  extent 
  in 
  the 
  vicinity 
  of 
  the 
  diabase 
  intrusions. 
  

   The 
  process 
  seems 
  to 
  have 
  been 
  largely 
  one 
  of 
  consolidation 
  through 
  

   baking. 
  A 
  limestone 
  specimen 
  obtained 
  near 
  the 
  diabase 
  intrusion 
  

   north 
  of 
  Zaca 
  Peak, 
  in 
  the 
  San 
  Rafael 
  Mountains, 
  gives 
  an 
  excellent 
  

   illustration 
  of 
  shearing. 
  The 
  calcite 
  crystals 
  have 
  all 
  been 
  arranged 
  

   parallel 
  and 
  greatly 
  elongated, 
  so 
  as 
  to 
  give 
  the 
  rock 
  a 
  schistose 
  

   structure. 
  

  

  STRUCTURE 
  AND 
  THICKNESS. 
  

  

  The 
  Monterey 
  has 
  nowhere 
  been 
  left 
  undisturbed. 
  In 
  places 
  it 
  

   has 
  been 
  but 
  gently 
  folded. 
  Pis. 
  IV 
  (p. 
  36), 
  VIII, 
  B 
  (p. 
  78), 
  and 
  IX 
  

   (p. 
  80) 
  show 
  examples 
  of 
  moderate 
  tilting. 
  But 
  at 
  other 
  places, 
  as 
  

   at 
  that 
  pictured 
  in 
  PL 
  VI, 
  B 
  (p. 
  46), 
  it 
  has 
  been 
  thrown 
  into 
  folds 
  

   so 
  sharp 
  and 
  closely 
  spaced 
  that 
  the 
  succession 
  of 
  the 
  beds 
  and 
  

   thickness 
  of 
  the 
  series 
  are 
  difficult 
  to 
  malgs 
  out. 
  The 
  details 
  of 
  its 
  

   structure 
  are 
  discussed 
  under 
  the 
  heading 
  " 
  Structure" 
  (pp. 
  76-78). 
  

   The 
  thickness 
  of 
  the 
  whole 
  series 
  is 
  at 
  least 
  5,200 
  feet. 
  Each 
  of 
  the 
  

   two 
  divisions 
  comprises 
  a 
  maximum 
  known 
  thickness 
  of 
  2,600 
  feet. 
  

   No 
  single 
  complete 
  section 
  of 
  the 
  whole 
  could 
  be 
  obtained. 
  

  

  EVIDENCE 
  OF 
  AGE. 
  

  

  A 
  paucity 
  of 
  recognizable 
  molluscan 
  fossils 
  is 
  one 
  of 
  the 
  prominent 
  

   characteristics 
  of 
  the 
  Monterey 
  in 
  this 
  region, 
  as 
  in 
  most 
  others 
  in 
  

   the 
  Coast 
  Ranges 
  where 
  it 
  outcrops. 
  Moreover, 
  the 
  other 
  fossils 
  

   that 
  it 
  contains 
  are 
  of 
  little 
  value 
  in 
  indicating 
  its 
  age. 
  Its 
  position 
  

   in 
  the 
  geologic 
  column 
  is 
  determined 
  by 
  the 
  lower 
  Miocene 
  fossils 
  

   found 
  just 
  below 
  its 
  base 
  in 
  the 
  Vaqueros 
  and 
  by 
  the 
  upper 
  Miocene 
  

   fossils 
  found 
  at 
  or 
  near 
  the 
  base 
  of 
  the 
  Fernando 
  formation, 
  which 
  

   lies 
  unoonformably 
  above 
  it. 
  

  

  The 
  following 
  two 
  species 
  of 
  mollusks 
  occur 
  in 
  the 
  Monterey 
  

   diatomaceous 
  shale 
  on 
  the 
  road 
  just 
  above 
  the 
  Pinal 
  Oil 
  Company's 
  

   office, 
  southeast 
  of 
  Orcutt: 
  Area 
  afT. 
  trilineata 
  Conrad, 
  Phacoides 
  

   aff 
  . 
  acutilineatus 
  Conrad. 
  

  

  