THE  EASTERN  PART  OF  THE  GREAT  DIVIDE  BASIN 
COAL  FIELD.  WYOMING.0 
By  E.  Eggleston  Smith. 
INTRODUCTION. 
The  Great  Divide  Basin  coal  field  is  situated  along  and  north  of  the 
Union  Pacific  Railroad  in  south-central  Wyoming,  and  embraces 
portions  of  the  northeast  end  of  Sweetwater  County,  the  northwest 
end  of  Carbon  County,  and  the  southeast  corner  of  Fremont 
County.  The  portion6  of  the  basin  covered  by  this  report  extends 
from  Rawlins  westward  along  the  Union  Pacific  Railroad  to  Tipton 
and  from  the  railroad  northward  to  the  Green  Mountains,  Muddy 
Creek  Gap,  and  the  Ferris  Mountains,  and  includes  Tps.  21  to  28  N., 
Rs.  88  to  92  W.;  Tps.  21  to  25  N.,  Rs.  93  to  96  W.;  and  portions  of 
T.  20  N.,  Rs.  90  to  96  W. 
A  detailed  reconnaissance  survey  was  made  of  this  region.  Geo- 
logic and  topographic  sketch  maps  were  constructed  on  the  scale  of 
2  inches  to  the  mile.  As  the  primary  object  of  the  survey  was  to 
classify  the  coal  land,  the  horizontal  control  was  based  entirely  on 
Land  Office  subdivisions.  Land  lines  were  paced  at  intervals  of 
one-half  mile  to  2  miles,  depending  on  the  character  of  the  relief, 
the  distribution  of  the  coal  outcrops,  and  the  complexity  of  the 
geology.  All  geologic  and  topographic  data  were  tied  to  the  nearest 
known  Government  corners  on  the  lines  thus  run.  *A  detailed 
topographic  base  map  on  the  scale  of  1  inch  to  the  mile  is  now  being 
constructed  from  the  field  sheets  and  will  be  included  in  the  final 
report.  This  map  will  show  the  geologic  structure  and  the  dis- 
tribution of  the  coal-bearing  formations,  the  outcrops  of  the  prin- 
cipal coal  beds,  the  location  of  coal  mines  and  prospects,  and  the 
surface  exposures  where  sections  of  coal  beds  were  measured. 
In  preparing  the  map  (PI.  XII)  accompanying  this  report  the 
lengths  of  the  land  lines  as  given  on  the  plats  of  the  original  Land 
Office  surveys  were   accepted   as  correct   and  were  plotted  by  so 
a  This  paper  is  a  preliminary  report  of  field  work  carried  on  by  the  writer,  assisted  by  W.  B.  Heroy, 
E.  B.  Hopkins,  William  Mulholland,  and  V.  H.  Barnett,  during  the  summer  of  1907.  A  final  report 
is  in  course  of  preparation  and  will  be  published  as  a  separate  bulletin. 
b  For  a  description  of  the  other  portions  of  the  Great  Divide  Basin,  see  reports  by  Max  W.  Ball  and 
Alfred  R.  Schultz  (pp.  243  and  256). 
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