IRON  ORES  IN  THE  UINTA  MOUNTAINS,  UTAH. 
By  J.  M.  Boutwell. 
INTRODUCTION. 
The  examination  of  the  economic  geology  of  the  Park  City  district, 
which  involved  the  first  detailed  geologic  mapping  in  the  Wasatch 
Range,  necessitated  an  investigation  of  broad  geologic  problems  in 
neighboring  regions  to  the  east  and  west.  Accordingly,  in  the  latter 
part  of  September,  the  general  geology  of  the  region  to  the  east  was 
studied  en  reconnaissance  by  the  writer,  with  the  assistance  of  Ellsworth 
Huntington.  This  region,  which  has  been  mapped  topographically  by 
this  survey  on  a  scale  of  2  miles  to  the  inch,  is  included  in  the  Coalville 
quadrangle,  which  extends  from  Echo  to  Heber  in  a  north-south  direc- 
tion, and  from  Park  Cit}^  nearly  to  the  headwaters  of  Weber  and  Provo 
rivers  in  an  east-west  direction.  It  embraces  an  area  of  approximately 
240  square  miles.  In  the  course  of  this  reconnaissance  deposits  of  rich, 
red  iron  ore  (hematite)  were  visited,  and  significant  geologic  data  were 
obtained.  The  purpose  of  this  sketch  is  to  present  the  essential  facts 
learned  about  these  iron  deposits.  In  order  that  these  facts  and  the 
problems  which  might  arise  in  connection  with  them  may  be  more 
clearly  understood,  the  broad  geographic  and  geologic  features  will  be 
described  and  new  data  on  the  unsettled  age  of  the  geo  logic  formations 
in  the  interior  of  the  range  will  be  presented. 
GEOGRAPHY. 
Location. — The  Uinta  Range  is  situated  in  greater  part  in  the  north- 
eastern part  of  Utah,  and  in  lesser  part  in  the  extreme  northwestern 
part  of  Colorado,  immediately  south  of  Wyoming.  In  about  the  lati- 
tude of  Salt  Lake  City  and  the  southern  shores  of  Great  Salt  Lake,  it 
extends  from  the  Wasatch  Range  eastward  approximately  150  miles, 
with  an  average  width  of  about  35  miles.  The  region  in  which  the 
principal  known  deposits  of  iron  ore  occur  is  near  the  central  part  and 
on  the  southwestern  slope  of  the  mountains. 
Topography. — The  general  form  of  the  range  is  an  elongated,  broad, 
flat-topped  arch.  As  the  main  east- west  divide  lies  north  of  the  center 
of  the  range,  a  north-south  profile  shows  unsymmetrical  slopes.     The 
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