﻿INTRODUCTION. 
  13 
  

  

  divisible 
  into 
  two 
  distinct 
  parts 
  — 
  the 
  upper, 
  the 
  bituminous 
  shales, 
  and 
  the 
  lower, 
  

   the 
  gypsiferous 
  clays. 
  Below 
  the 
  clays 
  are 
  sandstone, 
  shales, 
  and 
  conglomerates 
  

   resting 
  on 
  the 
  gabbro 
  and 
  serpentine. 
  * 
  * 
  * 
  The 
  strata 
  of 
  volcanic 
  ash 
  appear 
  in 
  

   the 
  lower 
  Miocene 
  beds. 
  There 
  are 
  three 
  distinct 
  horizons, 
  the 
  lowest 
  resting 
  on 
  the 
  

   gabbro. 
  

  

  The 
  igneous 
  rocks 
  are 
  treated 
  in 
  especial 
  detail 
  in 
  this 
  paper 
  and 
  

   a 
  very 
  good 
  description 
  is 
  given 
  of 
  the 
  bituminous 
  shales. 
  The 
  con- 
  

   clusions 
  of 
  the 
  present 
  writers 
  are 
  in 
  agreement 
  with 
  the 
  statements 
  

   above 
  quoted 
  and 
  the 
  others 
  contained 
  in 
  Fairbanks's 
  paper. 
  

  

  In 
  1901 
  George 
  H. 
  Eldridge 
  gave 
  an 
  admirable 
  general 
  outline 
  

   of 
  the 
  topography 
  and 
  geology 
  of 
  the 
  country 
  surrounding 
  the 
  

   Santa 
  Maria 
  field 
  in 
  his 
  treatise 
  on 
  u 
  The 
  asphalt 
  and 
  bituminous- 
  

   rock 
  deposits 
  of 
  the 
  United 
  States/' 
  and 
  discussed 
  in 
  detail 
  its 
  asphalt 
  

   deposits. 
  He 
  says: 
  

  

  The 
  geology 
  of 
  the 
  region 
  embraces 
  an 
  underlying 
  series 
  of 
  folded 
  Monterey 
  shale 
  

   of 
  both 
  the 
  soft 
  and 
  more 
  organic 
  material 
  and 
  that 
  which 
  is 
  hard 
  and 
  siliceous, 
  but 
  

   the 
  former 
  predominates. 
  So 
  far 
  as 
  observed 
  by 
  the 
  writer 
  this 
  series 
  of 
  beds 
  was 
  

   not 
  exposed 
  at 
  any 
  point 
  in 
  its 
  entirety. 
  Overlying 
  the 
  Monterey 
  unconformably, 
  

   and 
  especially 
  developed 
  in 
  La 
  Graciosa 
  Hills, 
  is 
  the 
  heavy 
  and 
  extensive 
  deposit 
  of 
  

   Pliocene 
  sands, 
  grits, 
  and 
  conglomerate 
  already 
  referred 
  to. 
  The 
  composition 
  of 
  the 
  

   later 
  deposit 
  is 
  chiefly 
  quartzose. 
  

  

  Eldridge 
  " 
  observed 
  a 
  prevailing 
  central 
  fold 
  somewhat 
  to 
  the 
  north 
  

   of 
  the 
  topographic 
  axis 
  of 
  the 
  ridge" 
  south 
  of 
  Waldorf, 
  in 
  the 
  Cas- 
  

   malia 
  Hills, 
  this 
  being 
  no 
  doubt 
  the 
  fold 
  described 
  in 
  the 
  present 
  report 
  

   as 
  the 
  Schumann 
  anticline. 
  He 
  says 
  further: 
  

  

  The 
  Pliocene 
  * 
  * 
  * 
  shows 
  a 
  less 
  degree 
  of 
  folding 
  than 
  the 
  underlying 
  Mon- 
  

   terey, 
  yet 
  the 
  movement 
  that 
  produced 
  the 
  pre-Pliocene 
  ridge 
  has 
  apparently 
  been 
  

   continued 
  subsequent 
  to 
  the 
  deposition 
  of 
  the 
  materials 
  of 
  this 
  age, 
  for 
  gentle 
  dips 
  

   of 
  from 
  2° 
  to 
  10° 
  are 
  to 
  be 
  observed 
  in 
  the 
  later 
  formation. 
  

  

  In 
  discussing 
  the 
  country 
  east 
  of 
  Los 
  Alamos, 
  between 
  the 
  San 
  

   Rafael 
  Range 
  and 
  the 
  Santa 
  Ynez 
  Valley, 
  which 
  he 
  calls 
  the 
  Los 
  

   Alamos 
  region, 
  Eldridge 
  says: 
  

  

  In 
  structure 
  the 
  Los 
  Alamos 
  region 
  presents 
  a 
  series 
  of 
  folds 
  which 
  are 
  in 
  general 
  

   coincident 
  with 
  the 
  topographic 
  ridges 
  and 
  valleys. 
  * 
  * 
  * 
  It 
  is 
  worthy 
  of 
  note 
  that 
  

   the 
  valleys 
  of 
  the 
  region 
  under 
  consideration 
  for 
  the 
  most 
  part 
  occupy 
  the 
  synclinal 
  

   troughs. 
  It 
  is 
  possible 
  that 
  some 
  of 
  them 
  also 
  occupy 
  fault 
  lines. 
  * 
  * 
  * 
  The 
  gen- 
  

   eral 
  trend 
  of 
  the 
  folds 
  for 
  the 
  Los 
  Alamos 
  district, 
  and 
  indeed 
  for 
  a 
  great 
  stretch 
  of 
  coun- 
  

   try 
  beyond, 
  is 
  N. 
  70° 
  to 
  80° 
  W., 
  the 
  dips 
  being 
  north 
  and 
  south. 
  Excepting 
  in 
  their 
  

   trend, 
  however, 
  there 
  is 
  but 
  little 
  regularity 
  in 
  the 
  disposition 
  of 
  the 
  folds, 
  and 
  their 
  

   axes, 
  both 
  longitudinal 
  and 
  transverse, 
  vary 
  greatly 
  in 
  length. 
  In 
  addition 
  to 
  the 
  

   main 
  and 
  conspicuous 
  folding 
  that 
  has 
  been 
  described, 
  there 
  are 
  frequent 
  crumples 
  

   of 
  minor 
  importance. 
  

  

  In 
  another 
  place 
  Eldridge 
  mentions 
  a 
  lens 
  of 
  limestone 
  included 
  

   in 
  the 
  serpentine 
  in 
  a 
  high 
  bluff 
  just 
  north 
  of 
  Alamo 
  Pintado 
  Creek, 
  

   along 
  the 
  old 
  beach 
  line 
  where 
  the 
  Fernando 
  was 
  deposited 
  upon 
  the 
  

   Franciscan 
  at 
  the 
  base 
  of 
  the 
  San 
  Rafael 
  Mountains. 
  This 
  lime- 
  

  

  o 
  Twenty-second 
  Ann. 
  Rept. 
  U. 
  S. 
  Geol. 
  Survey, 
  pt. 
  1, 
  1901, 
  pp. 
  424-441, 
  

   1784— 
  Bull. 
  322—07 
  2 
  

  

  