470  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1904.        [bull.  260. 
la  ted  thereon  to  a  depth  of  many  hundred  feet.  After  draining 
to  the  lowest  point  of  its  outlet,  the  lake  continued  to  shrink  under 
the  influence  of  evaporation,  recording  its  fall  during  halting  stages 
by  well-marked  shore  lines,  until  it  reached  its  present  state — a 
comparatively  small  body  in  the  lowest  portion  of  the  old  basin. 
Thus  a  topography  has  been  developed  which  is  characterized  by 
excessively  flat  stretches  of  desert  interrupted  by  narrow,  steep- 
sided,  deeply  dissected,  north-south  ranges,  with  their  lower  slopes 
contoured  by  shore  lines. 
The  rocks  composing  the  great  Wasatch  wall  and  the  Basin  ranges 
include  sandstones,  limestones,  and  schists,  which  were  considered 
by  the  geologist  of  the  Fortieth  Parallel  Survey  to  range  from 
Archean  to  later  Tertiary  in  age.  In  the  region  bordering  the 
area  under  discussion  the  Wasatch  section  embraces  rocks  ranging 
from  pre-Cambrian  to  Pliocene  Tertiary,  and  the  youngest  sedimen- 
tary rocks  mapped  in  the  neighboring  Basin  ranges  are  Carbon- 
iferous." 
The  lake  sediments  forming  the  intervening  stretches  are  clays, 
sands,  and  unconsolidated  conglomerates,  composed  of  material  shed 
from  adjoining  slopes,  and  also  carry  interbedded  plant  and  animal 
remains.  The  geological  problem  presented  is,  then,  to  ascertain 
whether  an  oil-  and  asphalt-bearing  series  occurs  in  these  unconsoli- 
dated sedimentary  fillings  or  in  the  underlying  bed  rock. 
OIL. 
Prospecting  for  oil  has  been  carried  on  at  several  points,  and  many 
hundred  claims  have  been  taken  up  along  the  eastern  and  northern 
shores  of  Great  Salt  Lake.  No  oil  has  yet  been  encountered  in  this 
vicinity,  though  boring  is  still  in  progress  at  the  Rozel  Hills.  About 
150  miles  farther  south,  at  Fillmore,  Utah,  a  small  amount  of  boring 
is  being  continued  with  a  view  to  tapping  commercial  quantities.  It 
is  understood  that  the  lower  portion  of  this  boring,  at  the  depth  where 
oil  was  struck,  was  in  bed  rock. 
The  next  deepest  boring  in  the  State  has  been  put  down  by  the 
Guffey  &  Galey  Company  about  a  mile  southwest  of  Farmington.  A 
depth  of  about  2,000  feet  has  been  attained,  and  the  results  of  that 
work  have  been  placed  at  the  service  of  this  Survey. 
Ground  Avas  selected  by  this  company  adjoining  that  from  which 
gas  was  obtained  for  a  limited  time  about  twelve  years  ago  for 
domestic  use  in  Salt  Lake  City.&  It  lies  in  a  belt  bordering  Great 
Salt  Lake,  which  has  been  exposed  by  the  recent  recession,  and  is 
"  TT.  S.  Geol.  Explor.  40th  Par.,  Geologic  Atlas  (Map  III,  west  half)  and  vol.  2,  p.  422. 
''The  data  regarding  this  former  gas  industry,  collected  by  G.  B.  Richardson  of  this  Sur- 
vey, are  presented  on  pages  480-483  of  this  volume. 
