﻿GEOLOGY. 
  49 
  

  

  of 
  solfataras 
  and 
  have 
  given 
  rise 
  to 
  the 
  opinion 
  that 
  volcanic 
  activity 
  

   is 
  present 
  in 
  this 
  region. 
  This 
  so-called 
  "Rincon 
  volcano" 
  existed 
  

   before 
  1855, 
  being 
  referred 
  to 
  in 
  the 
  Pacific 
  Railroad 
  reports; 
  this 
  

   shows 
  that 
  the 
  burning 
  has 
  continued 
  a 
  long 
  time. 
  

  

  TYPICAL 
  OCCURRENCES 
  OF 
  BURNT 
  SHALE. 
  

  

  Outcrops 
  of 
  burnt 
  shale 
  occur 
  in 
  eight 
  or 
  ten 
  localities 
  in 
  the 
  Santa 
  

   Maria 
  district. 
  The 
  best 
  examples 
  are 
  at 
  various 
  places 
  along 
  the 
  

   ridge 
  of 
  the 
  Casmalia 
  Hills 
  from 
  a 
  point 
  south 
  of 
  Schumann 
  to 
  

   Waldorf; 
  on 
  the 
  north 
  and 
  south 
  sides 
  of 
  Graciosa 
  Ridge; 
  and 
  on 
  

   Redrock 
  Mountain 
  4 
  miles 
  southeast 
  of 
  Los 
  Alamos. 
  In 
  each 
  of 
  

   these 
  regions 
  every 
  stage 
  of 
  alteration 
  is 
  exhibited, 
  from 
  the 
  slightly 
  

   discolored 
  shale 
  to 
  hard 
  slaglike 
  rocks 
  of 
  varying 
  shades 
  of 
  red 
  and 
  

   black. 
  The 
  area 
  of 
  altered 
  shale 
  in 
  the 
  different 
  localities 
  ranges 
  

   from 
  about 
  a 
  hundred 
  square 
  feet 
  to 
  a 
  half 
  a 
  square 
  mile 
  or 
  more, 
  as 
  

   at 
  Redrock 
  Mountain. 
  In 
  each 
  the 
  burnt 
  rock 
  is 
  surrounded 
  by 
  unal- 
  

   tered, 
  usually 
  soft, 
  white, 
  diatomaceous 
  shales 
  which 
  in 
  most 
  places 
  

   show 
  the 
  planes 
  of 
  stratification. 
  At 
  no 
  point 
  observed 
  was 
  a 
  sign 
  

   of 
  stratification 
  left 
  in 
  the 
  baked 
  shale. 
  In 
  every 
  occurrence 
  the 
  shales 
  

   in 
  the 
  neighborhood 
  are 
  bituminous 
  and 
  asphalt 
  deposits 
  are 
  usually 
  

   adjacent. 
  

  

  The 
  largest 
  area 
  of 
  altered 
  shale 
  is 
  on 
  the 
  summit 
  and 
  surrounding 
  

   ridges 
  of 
  Redrock 
  Mountain. 
  This 
  is 
  the 
  highest 
  of 
  the 
  hills 
  in 
  the 
  

   basin 
  region 
  between 
  the 
  San 
  Rafael 
  and 
  Santa 
  Ynez 
  mountains, 
  

   being 
  1,968 
  feet 
  above 
  the 
  sea; 
  the 
  height 
  of 
  most 
  of 
  the 
  summits 
  in 
  

   the 
  vicinity 
  is 
  from 
  1,000 
  to 
  1,500 
  feet. 
  Redrock 
  Mountain 
  seems 
  to 
  

   owe 
  its 
  prominence, 
  at 
  least 
  in 
  part, 
  to 
  the 
  metamorphosed 
  shale 
  that 
  

   forms 
  its 
  summit. 
  Likewise, 
  in 
  the 
  800-foot 
  hill 
  on 
  the 
  southeast 
  side 
  

   of 
  Schumann 
  Pass, 
  the 
  capping 
  of 
  this 
  same 
  character, 
  resembling 
  

   volcanic 
  rock, 
  seems 
  to 
  have 
  caused 
  the 
  topographic 
  relief. 
  The 
  

   metamorphism 
  in 
  these 
  localities 
  probably 
  took 
  place 
  a 
  long 
  time 
  

   ago. 
  At 
  Redrock 
  Mountain 
  great 
  deposits 
  of 
  asphalt 
  are 
  in 
  places 
  

   in 
  contact 
  with 
  the 
  altered 
  shale, 
  and 
  there 
  is 
  a 
  large 
  area 
  of 
  shale 
  

   impregnated 
  with 
  bitumen. 
  

  

  DEPTH 
  TO 
  WHICH 
  ALTERATION 
  HAS 
  EXTENDED. 
  

  

  The 
  depth 
  to 
  which 
  alteration 
  has 
  extended 
  below 
  the 
  surface 
  in 
  

   these 
  occurrences 
  is 
  difficult 
  to 
  determine. 
  A 
  cliff 
  of 
  burnt 
  shale 
  

   50 
  to 
  100 
  feet 
  high 
  is 
  exposed 
  4 
  J 
  miles 
  due 
  south 
  of 
  Guadalupe, 
  and 
  

   the 
  difference 
  of 
  elevation 
  of 
  points 
  in 
  the 
  Redrock 
  Mountain 
  neigh- 
  

   borhood 
  where 
  the 
  altered 
  rock 
  outcrops 
  amounts 
  to 
  several 
  hundred 
  

   feet. 
  That 
  such 
  metamorphism 
  of 
  the 
  shale 
  has 
  not 
  been 
  solely 
  a 
  

   surface 
  phenomenon 
  is 
  shown 
  by 
  the 
  fact 
  that 
  burnt 
  shale 
  has 
  been 
  

   found 
  at 
  considerable 
  depths 
  in 
  drilling. 
  Mr. 
  Orcutt, 
  of 
  the 
  Union 
  Oil 
  

   Company, 
  exhibited 
  samples 
  of 
  red 
  shale, 
  coming 
  from 
  depths 
  of 
  950 
  

  

  