﻿GEOLOGY. 
  55 
  

  

  It 
  would 
  be 
  difficult 
  to 
  work 
  out 
  the 
  limits 
  of 
  the 
  area 
  that 
  this 
  

   remnant 
  covers. 
  In 
  all 
  probability 
  it 
  is 
  very 
  small, 
  and 
  it 
  has 
  not 
  

   been 
  shown 
  on 
  the 
  map. 
  . 
  This 
  shale 
  here 
  forms 
  the 
  base 
  of 
  the 
  

   Fernando. 
  A 
  pebbly 
  layer 
  with 
  constituent 
  well-worn 
  pebbles 
  of 
  

   Monterey 
  shale 
  embedded 
  in 
  sand 
  has 
  aided 
  in 
  the 
  accumulation 
  of 
  

   asphalt 
  on 
  the 
  summit 
  of 
  the 
  ridge 
  near 
  by 
  ; 
  where 
  it 
  probably 
  marks 
  

   the 
  basal 
  line 
  of 
  the 
  Fernando 
  formation. 
  

  

  Above 
  the 
  soft 
  diatomaceous 
  or 
  gritty 
  shale 
  and 
  fine 
  white 
  sand 
  

   that 
  is 
  common 
  at 
  or 
  near 
  the 
  bottom 
  of 
  the 
  Fernando 
  the 
  bulk 
  of 
  

   the 
  formation 
  is 
  composed 
  of 
  rather 
  loosely 
  consolidated 
  fine 
  white 
  

   and 
  yellow 
  sand 
  and 
  coarser 
  gray 
  sand 
  that 
  grades 
  here 
  and 
  there 
  

   into 
  thick 
  beds 
  of 
  loose 
  conglomerate. 
  The 
  conglomerate 
  is 
  made 
  

   of 
  well-worn 
  pebbles, 
  mostly 
  of 
  flint 
  and 
  hard 
  shale, 
  embedded 
  in 
  a 
  

   coarse 
  sandy 
  matrix. 
  Locally 
  the 
  sand 
  and 
  conglomerate 
  are 
  ex- 
  

   tremely 
  hard, 
  owing 
  usually 
  to 
  the 
  presence 
  of 
  a 
  large 
  number 
  of 
  

   mollusk 
  shells 
  from 
  which 
  a 
  calcareous 
  cement 
  has 
  been 
  derived. 
  

   The 
  most 
  prominent 
  bed 
  of 
  conglomerate, 
  and 
  one 
  that 
  seems 
  to 
  be 
  

   constant 
  over 
  the 
  whole 
  region, 
  occurs 
  from 
  800 
  to 
  1,000 
  feet 
  up 
  in 
  

   the 
  series 
  (above 
  the 
  lowest 
  horizon) 
  just 
  north 
  of 
  Canada 
  de 
  los 
  

   Alisos, 
  on 
  La 
  Laguna 
  grant. 
  What 
  is 
  probably 
  the 
  same 
  bed 
  is 
  well 
  

   exposed 
  in 
  cliffs 
  west 
  of 
  Canada 
  Laguna 
  Seca, 
  1| 
  miles 
  south 
  of 
  the 
  

   Los 
  Alamos 
  Valley. 
  This 
  loose 
  aggregate 
  of 
  sand 
  and 
  pebbles 
  in 
  

   alternating 
  strata 
  of 
  coarse 
  and 
  fine 
  material 
  is 
  dominantly 
  com- 
  

   posed 
  of 
  the 
  light-colored 
  pebbles 
  of 
  Monterey 
  shale. 
  Pebbles 
  of 
  

   other 
  varieties 
  occur 
  more 
  sparingly. 
  Above 
  the 
  conglomerate 
  lies 
  

   a 
  stratum 
  of 
  limestone 
  that 
  is 
  constant 
  over 
  the 
  whole 
  region 
  and 
  

   seems 
  to 
  mark 
  a 
  division 
  in 
  the 
  Fernando. 
  There 
  are 
  two 
  or 
  more 
  

   massive 
  beds 
  of 
  hard 
  limestone 
  interbedded 
  with 
  soft, 
  gray, 
  very 
  

   alkaline, 
  earthy 
  material, 
  making 
  a 
  total 
  thickness 
  ranging 
  from 
  10 
  

   to 
  perhaps 
  50 
  feet. 
  Its 
  fossils 
  indicate 
  that 
  it 
  is 
  of 
  fresh-water 
  

   origin, 
  and 
  possibly 
  it 
  marks 
  the 
  base 
  of 
  a 
  fresh 
  or 
  brackish 
  water 
  

   series. 
  The 
  portion 
  of 
  the 
  Fernando 
  overlying 
  this 
  limestone 
  prob- 
  

   ably 
  corresponds 
  to 
  the 
  fresh-water 
  Paso 
  Robles 
  formation 
  of 
  the 
  

   Salinas 
  Valley 
  described 
  by 
  Fairbanks 
  in 
  the 
  San 
  Luis 
  folio. 
  In 
  

   some 
  places 
  where 
  this 
  higher 
  portion 
  of 
  the 
  Fernando 
  above 
  the 
  

   limestone 
  has 
  not 
  been 
  worn 
  away, 
  it 
  is 
  found 
  to 
  consist 
  of 
  little- 
  

   consolidated 
  beds 
  of 
  fine 
  sand, 
  gravel, 
  and 
  clay 
  that 
  look 
  as 
  if 
  they 
  

   might 
  have 
  been 
  laid 
  down 
  in 
  fresh 
  water, 
  but 
  no 
  proof 
  of 
  their 
  

   origin 
  has 
  been 
  found. 
  Such 
  beds 
  are 
  well 
  exposed 
  in 
  the 
  foothills 
  

   of 
  the 
  San 
  Rafael 
  Range 
  north 
  of 
  Santa 
  Ynez, 
  where 
  they 
  weather 
  

   characteristically 
  into 
  cliffs 
  at 
  the 
  summit 
  of 
  hills. 
  A 
  view 
  of 
  such 
  

   an 
  exposure 
  is 
  given 
  in 
  PI. 
  VI, 
  A 
  (p. 
  46), 
  which 
  affords 
  a 
  good 
  idea 
  of 
  

   the 
  rough 
  alternating 
  beds 
  of 
  coarse 
  material. 
  No 
  good 
  lithologic 
  or 
  

   paleontologic 
  criteria 
  are 
  known 
  by 
  which 
  this 
  series 
  may 
  be 
  sepa- 
  

   rated 
  from 
  the 
  lower 
  portion 
  of 
  the 
  Fernando, 
  and 
  they 
  are 
  there- 
  

   fore 
  mapped 
  as 
  a 
  unit. 
  

  

  