DIATOMACEOUS    DEPOSITS    IN    CALIFORNIA.  441 
the  area  covered,  but  it  is  many  square  miles.  It  forms  a  fringe  to 
the  hills,  structurally  overlying  the  hard,  contorted  lower  Monterey 
shale  that  forms  the  greater  portion  of  the  hills  for  several  miles  back 
from  the  valley.  On  the  sides  of  the  canyon  followed  by  a,  road 
into  the  hills  4  miles  west  of  Lompoc  about  1,000  feet  of  these  beds 
are  exposed  with  a  steep  northward  dip  toward  the  valley.  It  is 
probable  that  a  considerable  portion  of  the  sand-covered  hills  west 
of  this  road  as  far  as  Surf,  on  the  shore  of  the  Pacific,  is  occupied  by 
the  soft  shale  of  this  series.     The  covering  of  sand  is  thin. 
San  Julian  Ranclio. — Diatomaceous  shale,  white  and  fairly  pure, 
occurs  interbedded  with  hard  limestone  and  flinty  shale  at  the  base 
of  the  Monterey  formation  just  north  of  El  Jaro  Creek  at  the  point 
where  it  joins  Salsipuedes  Creek,  on  the  northern  border  of  the  San 
Julian  Ranclio,  in  the  foothills  of  the  Santa  Ynez  Range.  The 
amount  present  is  small  compared  with  the  deposits  higher  up  in 
the  formation,  as  near  Lompoc.  In  general,  the  lower  half  of  the 
Monterey  is  barren  of  soft  unaltered  diatomaceous  beds  and  the 
upper  half  is  almost  entirely  composed  of  them.  At  least  one  area 
of  pure  flaky  diatomaceous  earth  occurs  near  the  head  of  Ytias 
Creek,  but  the  region  has  not  been  carefully  traversed.  It  is  not 
probable  that  any  very  extensive  area  of  it  occurs  here. 
Other  deposits. — Diatomaceous  deposits  are  exposed  along  the  road 
that  follows  Santa  Ynez  River  east  of  Lompoc,  on  the  point  of  the 
hills  a  mile  southeast  of  the  mouth  of  Salsipuedes  Creek,  and  on  the 
point  near  the  western  edge  of  the  Santa  Rosa  grant.  At  these 
places  the  material  forms  a  cap  overlying  the  hard  shales,  but  there 
is  no  great  area  of  it. 
BURTON    MESA. 
Burton  Mesa  is  a  wide,  flat  terrace  of  Monterey  shale  capped  with 
a  horizontal  covering  (about  25  feet  deep)  of  recent  sand  and  gravel. 
Along  the  northern  border  of  the  mesa  and  up  the  canyons  running 
into  it  from  the  northwest  and  from  the  southeast  are  exposed  white 
diatomaceous  deposits,  and  this  material  constitutes  the  bulk  of  the 
northeastern  portion  of  the  mesa.  Earth  of  a  very  fine  quality 
forms  the  eastern  side  of  the  big  canyon  next  east  of  Pine  Canyon, 
from  5  to  8  miles  northeast  of  Lompoc,  and  thence  eastward  to  the 
point  where  the  mesa  merges  into  the  hilly  region  south  of  Harris 
the  valleys  dissecting  the  terrace  show  that  the  whole  region  is  com- 
posed of  this  material.  The  earth  continues  into  the  hills  farther 
east,  as  described  under  the  next  heading.  Good  exposures  in  which 
the  deposits  may  be  examined  occur  along  Santa  Lucia  Canyon  and 
the  valleys  running  into  it.  The -material  is  of  very  light  weight  and 
soft,  but  yet  compact.  The  bedding  is  thin,  but  as  the  earth  is  very 
homogeneous  the  bedding  planes  or  changes  from  one  bed  to  another 
