142  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,   1903.  [bull. 225. 
relation  during  the  present  season,  and  has  rendered  thereon  a  pre- 
liminary report. 
The  product  of  the  field  work  during  these  two  seasons  consists  of  a 
somewhat  detailed  knowledge  of   the  leading  events  in  the  geologic 
history  of  the  central  Wasatch  Mountains  and  vicinity,  a  large  body 
of  precise  geologic  data  regarding  the  immediate  Park  City  district, 
and  much  valuable  information  about  the  ore  deposits  of  the  camp. 
Obviously,  in  the  course  of  actual  field  work,  which  at  date  of  writing  | 
is  still  in  progress,  there  has  been  no  suitable  opportunity  for  thorough  j 
correlation  of  field  data.     Before  final  conclusions  can  be  reached,  such  J 
correlation  and  systematic  office  study  of  this  material  will  be  required. 
Certain  results,  however,  which  it  is  hardly  expected  will  be  materially  j 
altered  by  further  study  and  which  are  of  direct  significance  in  cur- 
rent  exploration  and  exploitation,  may  be  tentatively  stated  for  imme-i 
diate  utilization.     It  is  to  be  clearly  understood,  however,  that  these! 
preliminary  statements  in  this   rough,   generalized   field  sketch  are! 
subject  to  such  modifications  as  may  be  required  by  further  studies. 
In  the  first  report  of  progress  brief  descriptions  were  given  regard- 1 
ing  the  general  geology  and  geography  of  the  region,  and  the  location 
and  history  of  this  district.  For  such  particulars  the  reader  is  referred 
to  that  report.  The  present  abstract  will  be  confined  to  presenting  in 
a  brief,  generalized  form  some  of  the  additional  information  regarding 
this  immediate  district  which  has  been  procured  during  the  last  season. 
This  information  falls  naturally  into  two  main  divisions,  namely, 
that  relating  to  areal  geology  and  that  relating  to  economic  geology. 
Under  "Areal  geology"  the  sedimentary  rocks,  metamorphic  rocks,  and 
structure  will  be  described;  under  "Economic  geology,"  the  grade  of 
ores,  occurrence  of  ores,  exploitation,  recent  industrial  progress,  and 
recent  production  will  be  considered. 
AREAL  GEOLOGY. 
Sedimentary  rocks. — The  sedimentary  rocks  of  the  Park  City  district 
include  quartzites,  sandstones,  shales,  and  limestones.  They  consti- 
tute, according  to  their  lithologic  character  and  paleontologic  contents, 
five  distinct  geologic  formations.     These  are,  from  older  to  younger, 
(1)  a  massive  quartzite,  approximately  1,500  to  2,000  feet  in  thickness; 
(2)  a  calcareous  series  made  up  of  normal  limestones,  considerable 
sandstone,  and  some  shale,  varying  several  hundred  feet  in  thickness, 
from  600  feet  upward;  (3)  a  red  shale  with  intercalated  thin,  argillaceous 
limestone  and  varicolored  shales,  ranging  in  thickness  from  1,000  to 
several  hundred  feet  less;  (4)  a  calcareous  sandstone,  normal  sandstone, 
and  varicolored  shales,  approximately  1,200  feet  in  thickness,  and  (5) 
red  shale  with  intercalated  thin,  fossiliferous  limestones  and  calcare- 
ous sandstones,  capped  by  coarse,  conglomeratic,  quartzitic  sandstone, 
approximately  1,000  feet  in  thickness.     This  group  of  five  formations 
