boutwell.]    OIL   AND    ASPHALT    IN    SALT    LAKE    BASIN,    UTAH. 
469 
shores  of  Great  Salt  Lake,  from  10  to  C>0  miles  northwest  of  Salt 
Lake  City.  The  areas  are  situated  in  the  extreme  eastern  part  of 
the  Great  Basin  and  comprise  a  portion  of  the  bed  of  Lake  Bonne- 
ville. Solution  of  the  practical  geologic  problems  which  are  met 
in  the  exploration  of  these  areas  thus  involves  an  understanding 
of  the  geologic  history  recorded  by  these  two  great  features. 
The  Great  Basin  is,  broadly  viewed,  a  vast  plain  walled  in  by 
the  massive  Sierra  Nevada  on  the  west  and  by  the  lofty 
Wasatch  Range  on  the  east,  and  is  interrupted  by  numerous  linear 
north-south  mountain  ranges.  The  portions  of  these  Basin  ranges 
now  visible  are  in  many  cases  only  the  crests  of  once  loftv  ranges 
113° 
111" 
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Salt-Lake 
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111 
Scale 
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5o  mile; 
A.  Rozel  asphalt  field  O.   Farmmgton   oil  prospect 
Fig.  22. — Map  of  northern  Utah,  showing  location  of  oil  and  asphalt  prospects. 
which  are  now  buried  to  unproved  depths  under  waste  deposits. 
At  a  comparatively  recent  date  a  depression  on  the  extreme  eastern 
side  of  the  basin  was  occupied  by  an  inland  sea  which  washed  th'> 
slopes  of  the  Wasatch  wall  and  extended  westward  into  the  present 
State  of  Nevada,  southward  to  cover  the  present  Escalante  Desert 
in  Iron  County,  northward  into  Idaho,  encompassed  several  of  the 
present  Basin  ranges,  making  them  islands,  and  overflowed  through 
Red  Elock  Pass  into  the  Snake  River  system.  Its  extent  and  his- 
tory are  recorded  by  the  prominent  shore  lines  which  characterize 
the  slopes  of  elevations  throughout  this  area.  Waste  from  the  sur- 
mounting land  masses  passed  into  this  lake,  covered  the  submerged 
mountain    slopes    and    intermontane    rock    bottoms,    and    accumu- 
