﻿GEOLOGY. 
  6 
  1 
  

  

  inclined 
  slightly 
  toward 
  the 
  ocean 
  or 
  the 
  line 
  of 
  drainage, 
  and 
  ranging 
  

   in 
  size 
  from 
  tens 
  of 
  square 
  miles 
  to 
  only 
  a 
  few 
  feet 
  square. 
  The 
  more 
  

   extended 
  terraces 
  fringe 
  the 
  coast 
  line 
  and 
  the 
  larger 
  valleys 
  and 
  

   cover 
  areas 
  of 
  low 
  hills. 
  The 
  smaller 
  ones 
  are 
  scattered 
  over 
  ridges 
  

   and 
  hilltops 
  and 
  along 
  the 
  smaller 
  valleys. 
  These 
  terraces 
  are 
  cov- 
  

   ered 
  with 
  a 
  thin 
  coating 
  of 
  sand 
  and 
  gravel, 
  and 
  here 
  and 
  there 
  with 
  

   clayey 
  material. 
  The 
  distribution 
  of 
  the 
  deposits 
  is 
  well 
  shown 
  on 
  

   the 
  map, 
  with 
  two 
  general 
  exceptions. 
  In 
  the 
  first 
  place, 
  many 
  of 
  

   the 
  strips 
  of 
  land 
  along 
  valleys 
  mapped 
  as 
  covered 
  with 
  terrace 
  

   deposits 
  may 
  not 
  represent 
  true 
  terraces, 
  as 
  it 
  is 
  almost 
  impossible 
  

   to 
  draw 
  definite 
  distinctions 
  between 
  such 
  horizontally 
  bedded 
  val- 
  

   ley 
  fillings, 
  true 
  terrace 
  cappings, 
  and 
  recent 
  alluvium. 
  All 
  post- 
  

   Fernando 
  deposits 
  in 
  small 
  valleys 
  are 
  therefore 
  mapped 
  with 
  the 
  

   terrace 
  formation, 
  and 
  alluvium 
  is 
  shown 
  only 
  in 
  the 
  extended 
  valley 
  

   bottoms, 
  where 
  dividing 
  lines 
  between 
  it 
  and 
  the 
  terrace 
  deposits 
  are 
  

   drawn 
  arbitrarily. 
  In 
  the 
  second 
  place, 
  owing 
  to 
  the 
  lithologic 
  simi- 
  

   larity 
  of 
  the 
  Fernando 
  and 
  the 
  terrace-deposit 
  sand 
  and 
  the 
  similar 
  

   surface 
  appearance 
  of 
  these 
  two 
  formations, 
  the 
  attempt 
  has 
  been 
  

   made 
  to 
  represent 
  on 
  the 
  map 
  only 
  a 
  few 
  areas 
  of 
  the 
  terrace 
  sand 
  

   overlying 
  the 
  Fernando. 
  The 
  Fernando 
  is 
  doubtless 
  capped 
  by 
  ter- 
  

   race 
  deposits 
  in 
  many 
  places, 
  but 
  it 
  is 
  usually 
  impossible 
  to 
  tell 
  

   whether 
  this 
  is 
  true 
  or 
  not. 
  The 
  lines 
  of 
  contact 
  between 
  these 
  for- 
  

   mations 
  are 
  of 
  necessity 
  arbitrarily 
  shown. 
  

  

  This 
  similarity 
  causes 
  much 
  difficulty 
  in 
  places 
  in 
  determining 
  

   whether 
  the 
  deposits 
  belong 
  to 
  the 
  Fernando 
  or 
  to 
  the 
  later 
  epoch, 
  

   and 
  whether 
  it 
  is 
  necessary 
  to 
  go 
  through 
  a 
  great 
  thickness 
  of 
  Fer- 
  

   nando 
  beds 
  or 
  only 
  a 
  few 
  feet 
  to 
  reach 
  the 
  Monterey 
  below. 
  Where 
  

   fossils, 
  distinct 
  lines 
  of 
  bedding, 
  or 
  tilted 
  strata 
  are 
  present 
  they 
  are 
  

   indications 
  that 
  the 
  sand 
  belongs 
  to 
  the 
  Fernando. 
  

  

  The 
  terraces 
  are 
  found 
  commonly 
  at 
  all 
  altitudes 
  up 
  to 
  1,200 
  reet, 
  

   and 
  a 
  few 
  even 
  as 
  high 
  as 
  1,400 
  feet. 
  None 
  have 
  been 
  definitely 
  rec- 
  

   ognized 
  at 
  a 
  higher 
  elevation. 
  

  

  LITHOLOGIC 
  CHARACTER. 
  

  

  The 
  material 
  of 
  the 
  terrace 
  deposits 
  is 
  usually 
  sand 
  and 
  conglomer- 
  

   ate, 
  for 
  the 
  most 
  part 
  the 
  former. 
  The 
  sand 
  is 
  medium 
  grained 
  and 
  

   contains 
  scattering 
  waterworn 
  pebbles. 
  It 
  is 
  normally 
  soft 
  and 
  

   grayish, 
  but 
  in 
  many 
  places 
  compact, 
  being 
  stained 
  a 
  reddish 
  yellow 
  

   and 
  hardened 
  by 
  iron 
  oxide 
  or 
  filled 
  with 
  iron-stained 
  concretions. 
  

   In 
  this 
  surficially 
  compacted 
  state 
  it 
  forms 
  hard 
  cappings 
  on 
  hilltops 
  

   and 
  slopes. 
  Round, 
  bullet-like, 
  iron-hardened 
  concretions 
  are 
  char- 
  

   acteristic 
  of 
  the 
  derived 
  soil. 
  Over 
  much 
  of 
  the 
  surface 
  of 
  Burton 
  

   Mesa 
  and 
  in 
  other 
  places 
  this 
  deposit 
  occurs 
  as 
  loose, 
  grayish 
  sand, 
  

   hardened 
  locally 
  by 
  the 
  action 
  of 
  rain 
  water 
  and 
  various 
  salts 
  or 
  

   oxide 
  of 
  iron. 
  The 
  conglomerate 
  — 
  or 
  gravel, 
  as 
  it 
  might 
  equally 
  well 
  

   1784— 
  Bull. 
  322—07 
  5 
  

  

  