442  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1906,    PART    I. 
are  not  marked.     A  block  may  be  split  into  flat  plates  of  almost  ai 
degree  of  thinness.     Santa   Lucia  Canyon  cuts  across  the  strike 
the  beds,  which  dip  at   a  very  low  angle,  about    12°  on  the  averagl 
toward  the  northeast.     The  thickness  of  the  series  within  the  limit 
in  which  it  consists  of  pure  diatomaceous  earth  is  at  least  'J, 000  feel 
The  beds  exposed  along  the  northern  edge  o\'  the  mesa  east   of 
point  2  miles  from  the  ocean  are  similar,  and  it  is  probable  that  thj 
region  between  this  point  and  Santa  Lucia  Canyon,  comprising  the 
whole   northeastern    corner   i)i'   the    mesa,    is   composed    of   the   same- 
material.     The  area  so  included  is  at  least    L2  or  1  ">  square  miles  in, 
extent . 
HILLS    BETWEEN     SANTA     JTNEZ     \M>    LOS     ALAMOS    VALLEYS. 
South  •>/'  Harris.  The  ridge  of  hills  between  the  Mission  La  Purl 
sima  grant  and  Harris  i^  composed  of  the  upper  part  of  the  Mon- 
terey formation,  which  is  overlain  by  more  recent  sand  deposits  on  I 
the  Hank-  of  the  ridge.  The  new  road  from  Lompoc  to  Harris 
exposes  a  thickness  of  at  least  2,400  feet,  which  is  almost  entirely 
soft  white  shale  composed  of  diatom  remains.  The  beds  dip  north- 
ward at  angles  <A'  20°  to  40°.  Some  of  the  material  is  of  less  pure 
quality  than  the  best,  and  there  are  a  few  layers  of  brown  brittll 
shale  or  yellowish-white  porcelainlike  shale,  but  the  great  bulk  of  it 
would  he  very  suitable  for  economic  use.  It  is  extremely  soft,  and 
blocks  of  any  size  or  shape  can  he  cut  out.  A  knife  or  saw  or  other 
cutting  instrument  will  go  through  it  just  as  through  soft  chalk. 
The  same  is  tine  of  the  shale  of  the  other  occurrences  mentioned  ill 
t  bis  paper. 
Similar  diatomaceous  earth  composes  I  he  whole  ridge  west  of  th< 
new  road  as  far  as  Burton  Mesa.  Locally  it  is  covered  by  terrac< 
-and.  hut  this  is  only  a  thin  capping  a  few  feet  in  depth.  There  i; 
an  available  area  of  at  least  7  or  8  square  miles  of  the  earth,  and 
when  the  thickness  of  the  series  is  considered  it  becomes  evident 
that  a  vast  amount  of  the  material  is  present. 
Between  Cebada  Canyon  <in<l  La  Zaca  Creelc.  In  most  of  the  hill} 
region  between  Cebada  Canyon  and  La  Zaca  Creek,  for  an  extent  oj 
over  30  square  mile-,  the  diatomaceous  shale  predominates  as  tin 
surface  formation.  Much  of  it  is  somewhat  altered  to  impure  varie- 
ties that  would  not  he  the  best  for  economic  purposes,  hut  areas 
of  many  square  miles  ate  covered  by  deposits  hundreds  of  feet 
thick  that  are  of  excellent  quality.  Areas  of  especially  good  mate- 
rial lie  just  north  of  Santa  Kit  a  all  along  the  ridge  for  many  miles 
west  of  Redrock  Mountain  and  over  the  hills  north,  northeast,  and 
southeast  of  that  mountain.  The  thickness  of  the  series  that  is 
exposed,  all  of  which  seems  to  he  with  little  doubt  of  diatomaceous 
origin,  whether  now  remaining  in  the  original  soft  state  in  which  it 
