360  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,   1905. 
The  strictly  local  structure  of  the  field  under  discussion  will  be  more  fully  comprehend* 
if  its  description  is  prefaced  by  a  word  in  regard  to  the  general  structure  of  the  Los  AngeL 
district  as  a  whole.     Practically  all  the  productive  oil  sands  of  the  different   Los  Angela 
fields  lie  on  the  south  limb  of  a  flexure,  usually  a  more  or  less  well-defined  anticline,  who* 
axis  extends  in  a  westerly  direction  from  the  vicinity  of  the  Catholic  cemetery  on  Buenl 
Vista  street  to  the  region  approximately  half  a  mile  north  of  West  lake  Park,  where  ii  bene  i 
about  20°  north  and  extends  to  a  poinl  about  three-fourths  of  a  mile  southeast  of  Colegrof 
and  something  over  a  mile  northeasl  of  Lhe  Salt  Lake  field.     Here  it  appears  lo  bend  to  th  l! 
north   again,   probably  trending  about    X.  60°  W.      In  the  Los  Angeles  <  i\y  field — that   if 
between  the  Catholic  <  emetery  and  the  Westlake  Park  region — the  south  limb  of  the  flexui 
dips  normally  a     angles  varying  from  30°  to  80°,  while  to  the  west,  along  that  portion 
having  a  northwesterly  trend,  the  dips  flatten  to  20°  or  25°.     The  Sal.   Lake  oil  field  i 
located  on  the  northwestern  Hank  of  a.  minor  hut  probably  somewhat  <  omplex  fold  or  flexui 
developed  <>n   the  comparative!}    low-dipping  southwest    limb  of  the  major  flexure  jus 
described. 
The  exact  nature  of  the  local  flexure  is  not  known,  but  it  is  probably  an  anticline,  possiblj 
complicated  by  faulting,  with  its  axis  extending  in  a  general  nort  heast -southwest  direct  iol 
The  available  evidence  appears  to  indicate  t  hat  the  flexure  extends  from  near  the  center  c 
the  SE.  I  sec.  1."..  T.  1  S.,  R.  14  \V..  at  least  as  far  as  the  lagoon  in  theSW.  \  sec.  21,  b| 
whether  or  not  it  cont  inues  fart  her  to  1  he  sout  hwest  is  problemat  i<  al.     The  large  a<  <  umula- 
tions  of  brea  in  the  immediate  vicinity  of  the  lagoon  and  to  flu1  north  and  northwest  of  if ,  in 
addit  ion  to  1  he  constant  ly  exuding  oil  and  es<  aping  gas  over  t  he  same  area,  indicate  some 
sort  of  a  profound  local  disturbance  or  fracture  in  the  underlying  beds.     If  this  disturbance 
has  an  extensive  longitudinal  dimension  in  a  northwesterly  direction  from  the  lagoon, 
some  of  the  evidence  appears  to  suggest  ,  then  ii  is  possible  thai  this  nort  hwesterly  f  rending 
disturbance  may  cut  off  the  Salt   Lake  flexure  from  a  southwesterly  extension  beyond  the 
lagoon.     If.  however,  the  disturbance  in  the  vicinity  of  the  lagoon  is  of  the  nature  of  a 
local  bulge  or  dome  in  the  underlying  beds,  ii   is  \c\y  likely  that   the  Salt   Lake  flexure  may 
have  a  considerable  southwestern  prolongation. 
The  map  '  iiur-  I'-',  p.  358),  on  whi<  h  the  dotted  contour  lines  show  the  probable  distance  of 
the  top  of  the  uppermost  important  oil  sand  below  the  Los  Angeles  i  \  datum  (255  feet 
above  sea,  level  ,  illust  rates  the  writer's  ideas  con<  erning  thesf  ructure  of  the  norl  hwest  limb 
of  the  Salt  Lake  flexure,  from  this  ii  will  be  seen  that  the  strike  of  the  oil  sand  swings 
around  from  a  nearly  east-west  line  in  the  region  north  of  the  lagoon  to  a  direction  slightly 
west  of  north  intheNE.  :,  sec.  21 .  The  dip  of  the  sand  in  the  region  about  the<  enter  of  sec.  21 
does  not  appear  to  be  much  more  than  10°  or  15°,  but  ii  increases  rapidly  in  steepness  both 
southeast  up  and  northwesl  down  the  dip.  T  le  region  im  nedia  ely  sou  heast  of  the  Salt 
Lake  flexure,  although  supporting  some  small  producing  w  ells  one  of  which  attains  a  depih 
of  nearly  3,000  feci  does  not  compare  in  productiveness  with  the  territory  to  the  north! 
west.  This  condition  may  be  explained  on  several  hypotheses,  lhe  two  most  probable 
being  either  (a)  that  the  Salt  Lake  flexure  is  accompanied  by  faulting  which  has  dropped 
the  productive  sands  on  the  southeast  down  out  of  reach  of  the  drill  or  raised  them  up  to 
such  an  elevation  that  they  were  eroded  away  in  a  period  subsequent  lo  the  faulting,  or 
i  A  i  thai  lhe  continuation  of  the  productive  beds  passes  over  the  flexure  (in  this  case  an 
anticline)  and  down  on  the  southeastern  flank,  but  under  conditions  unsuited  to  t  he  accumu-l 
la  ion  of  the  oil  in  the  large  quantities  encountered  on  the  northwestern  limb. 
Suggestions  for  futun  development.  Anyone  at  all  familiar  with  the  conditions  of  occur! 
rence  of  petroleum  in  the  California  fields  knows  that  any  but  the  most  tentative  predic- 
tion- as  to  the  location  of  the  oil  are  extremely  hazardous.  The  following  suggestions] 
based  on  the  evidence  in  hand,  ah  hough  lacking  definiteness  for  the  reasons  above  staled, 
may  be  of  some  assistance  to  those  engaged  in  developing  this  field. 
Ii  seem-  probable  that  the  produ<  f  ive  zone  of  I  he  Sail  Lake  field  extends  northward,  and 
possibly  a  little  westward,  from  the  territory  now  developed  Just  where  the  northern 
limit  is  located  is  problematical,  but  it  is  quite  certain  that  it  is  considerably  south  of  the 
