298         CONTRIBUTIONS   TO   ECONOMIC  GEOLOGY,   1907,   PART   II. 
vicinity  of  Raven  Park  the  rocks  spread  out  in  broader  folds  and 
cover  an  extensive  territory,  reaching  from  the  vicinity  of  Blue 
Mountain  on  the  north  to  a  line  within  a  few  miles  of  the  Book  Cliffs 
divide  at  the  head  of  Douglas  Creek  on  the  south.  Northwest  of 
Raven  Park  the  coal-bearing  strata  have  been  traced  continuously 
into  Utah  as  a  narrowing  belt,  which  is  described  in  a  subsequent 
section  of  this  paper  as  the  Vernal  field. 
The  examination  of  the  lower  White  River  field  was  commenced 
in  Tps.  4  and  5  N.,  R.  96  W.,  and  continued  westward  along  the  out- 
crops of  the  coal-bearing  rocks,  as  indicated  on  the  map  (PL  XVII). 
AGE    OF    COAL-BEARING    ROCKS. 
As  explained  briefly  under  the  heading  "  Stratigraphy,"  the 
Mesaverde  constitutes  the  only  important  coal-bearing  formation 
of  the  lower  White  River  field,  the  Laramie  being  absent  from  the 
geologic  section  south  of  Axial  Basin.  Furthermore,  the  post- 
Laramie  formations  appear  to  be  barren  of  valuable  coals,  and  it  is 
still  uncertain  if  any  of  the  strata  of  the  Grand  River  Basin,  of  which 
the  White  River  field  is  a  part,  are  strictly  to  be  correlated  with  the 
coal-bearing  strata  that  overlie  the  Laramie  beds  of  the  Yampa  field. 
The  correlation  of  the  basal  Tertiary  beds  of  the  two  fields  will  there- 
fore be  left  an  open  question  for  the  present,  as  it  is  necessary  to  dis- 
cuss here  only  the  Mesaverde  beds  in  the  fields  of  the  southern  basin. 
SUBDIVISION    OF    THE    WHITE    RIVER    FIELD. 
The  lower  White  River  field  is  considered  in  two  parts  as  divided 
at  the  base  line,  and  is  represented  in  this  way  on  Pis.  XVII  and  XVIII. 
This  is  done  partly  as  a  matter  of  convenience  for  publication  of  the 
maps  and  partly  to  separate  the  results  of  the  more  detailed  examina- 
tion made  north  of  the  base  line  from  those  of  the  hasty  reconnais- 
sance of  the  area  south  of  the  line.  Most  of  the  territory  north  of  the 
base  line  has  been  either  recently  resurveyed  by  the  General  Land 
Office,  or  the  contracts  have  been  let  and  it  is  expected  that  the  work 
will  be  completed  in  the  near  future.  On  the  other  hand,  in  the 
territory  south  of  the  base  line  and  west  of  the  twelfth  auxiliary 
guide  meridian,  the  old  land  surveys  are  believed  to  be  in  large  part 
practically  without  value,  and  very  few  corners  were  discovered  in  the 
present  investigation.  In  the  Douglas  Creek  drainage  basin  only 
three  land  corners  were  found,  and  these  do  not  appear  to  check  with 
each  other  nor  to  agree  with  their  stated  distances  and  directions 
from  the  base  line.  These  corners  are  situated  in  the  immediate 
valley  of  Douglas  Creek,  and  it  is  extremely  doubtful  if  many  corners 
were  ever  set  or  if  the  lines  were  run  at  all  in  the  adjoining  hills.  An 
attempt  to  classify  the  lands  in  this  southern  area,  therefore,  seems 
unwarranted  at  present. 
