306         CONTRIBUTIONS   TO   ECONOMIC   GEOLOGY,    1907,    PART   II. 
VERNAL  FIELD. 
LOCATION    AND    SETTLEMENT. 
The  valley  of  Ashley  Creek,  in  which  the  town  of  Vernal,  Utah,  is 
situated,  contains  perhaps  the  most  extensive  settlement  in  this  part 
of  the  State,  or  at  least  in  the  northern  part  of  Uinta  County.  This 
district  supports  a  prosperous  agricultural  community  of  considerable 
importance. 
CHARACTER  OF  THE  UTAH  LAND  SURVEYS. 
West  of  the  State  line  and  east  of  the  Green  River  valley  no  land- 
survey  corners  were  found  that  could  be  identified  with  any  certainty, 
and  although  some  satisfactory  surveys  may  at  one  time  have  been 
made  in  this  territory  it  seems  very  likely  that  the  corners  if  ever 
established  were  not  permanently  marked,  and  that  only  slight  and 
rather  uncertain  evidence  of  them  remains  to-day.  It  also  seems  clear 
that  the  original  surveys  of  Utah  overlapped  the  Colorado  State  line. 
This  was  probably  due  to  the  uncertainty  regarding  the  correct 
location  of  that  boundary  at  the  time  of  the  work. 
The  map  of  the  Vernal  field  presented  here  depends  for  its  ad- 
justment primarily  on  the  control  obtained  from  a  railroad  survey 
extending  from  Colorado  down  Cliff  Creek  to  Green  River,  and  also 
on  plane-table  traverse  and  triangulation  done  during  the  present 
investigation.  The  land  lines  east  of  Green  River  shown  on  the  map 
are  projected  through  from  corners  found  in  the  valley  lands.  West 
of  Green  River  the  more  extensive  settlement  and  farming  lands  laid 
out  by  subdivisions  and  largely  fenced  afforded  more  complete  evi- 
dence of  the  land-survey  system. 
RELATIONS    TO    THE    COLORADO    FIELDS. 
As  shown  by  PL  XIX,  the  Mesaverde  coals  in  this  part  of  the  Uinta 
Basin  are  directly  connected  with  the  same  group  in  the  White  River 
fields  of  Colorado,  but  the  State  line  offers  a  convenient  division  line 
for  the  separation  of  the  Utah  portion,  in  which  these  coals  have  not 
as  yet  been  shown  to  be  of  much  importance,  at  least  in  comparison 
with  the  richer  and  more  extensive  deposits  of  Colorado. 
An  additionally  distinctive  feature  is  shown  by  the  Utah  fields  in 
the  fact  that  as  the  Mesaverde  coals  become  relatively  unimportant, 
older  strata  at  the  base  of  the  Mancos  shale  develop  workable  beds, 
which  at  the  present  time  carry  the  only  coal  considered  worth 
exploitation  in  or  near  this  part  of  the  Green  River  valley. 
MESAVERDE    COAL. 
Tracing  of  the  Mesaverde  formation. — West  of  the  State  line  the  basal 
sandstones  of  the  Mesaverde  are  the  most  conspicuous  members  of 
that  formation,  constituting  a  rim-rock  ridge  somewhat  analogous 
