THE  YAMPA  COAL  FIELD,  ROUTT  COUNTY,  COLO.1 
I>\   X.  M.  Fenneman  and    Hoyt  S.  Gale. 
LOCATION. 
Tin'  existence  of  importanl  coal  resources  in  northwestern  Colorado  has  been  known  for 
many  years.  The  region  of  greatest  interesi  is  in  the  eastern  half  of  Routt  County,  lyingj 
in  the  upper  valley  of  Yampa  River.  The  area  covered  by  this  survey  of  the  field  is  approxi- 
mately 1,200  square  miles  and  this  is  practically  the  extent  of  the  Yampa  coal  field.  It 
lies  ;it  the  western  foot  of  the  Park  Range  of  the  Rocky  Mountains.  On  the  north  are  the 
high  peaks  and  ridges  of  the  Elkhead  Mountains.  On  the  south  the  held  is  interrupted  by 
an  east-west  anticlinal  fold  through  Axial  Basin,  supposed  to  the  be  eastward  extension  or 
the  Qinta  uplift,  which  merges  into  the  White  River  Plateau.  To  the  west  and  northwest 
the  coal-bearing  rocks  extend  to  an  undetermined  distance,  disappearing  beneath  forma- 
tions of  later  age. 
The  coal  held  lies  approximately  midway  between  the  Union  Pacific  Railroad  on  the  north 
and  the  Denver  and  Rio  Grande  Railroad  on  the  south.  Steamboat  Springs,  the  most 
prominent  town  of  the  district,  is  usually  reached  by  stage  from  Wolcott,  Colo.  The  held 
is  also  reached  by  stage  from  Middle  Park  and  Rifle.  Colo.,  and  from  Rawlins,  Wyo.  A 
number  of  regular  stage  lines  run  through  t  he  held. 
The  prospect  of  a  railroad  through  the  center  of  the  area  has  in  recent  years  stimulate! 
exploration  and  careful  study.  It  seems  almost  certain  that  with  more  adequate  transpor- 
tation facilities  the  Yampa  coal  field  will  become  an  importanl  factor  in  the  supply  of  the 
western  market.  The  coals  are  for  the  most  part  a  good  grade  of  bituminous,  and  anthracite 
of  good  quality  is  known  to  exist  within  a  certain  limited  area. 
The  held  centers  about  a  broad  area  of  rolling  country,  of  characteristically  smooth 
slopes,  although  at  places  showing  considerable  relief.  This  is  bounded  by  a  sharply  dis- 
sected tin  i  of  sandstone  ridges  rising  to  1 .200  or  I  ,."00  feet  above  the  drainage  level.  Yampa 
River  cuts  across  the  field  in  a  westerly  course,  flowing  through  broad,  open  bottom  lands 
where  the  course  lies  over  the  -oft  rocks  of  the  prairie  land  and  through  canyons  where  it 
has  cut  across  the  sandstone  ridges. 
STRUCTURE. 
This  coal  field  as  a  whole  is  a  well-defined  st  ructura  1  unit.  It  is  t  he  ext  reme  southeaster! 
point  of  a  huge  synclinal  basin  of  the  coal-bearing  rocks,  the  axis  of  which  passes  al  .  oM 
directly  through  the  towns  of  Yampa  and  Harden.  Since  the  basin  as  a  whole  plunges  to 
the  northwest,  the  beds  along  the  axis  dip  in  that  direction.  Following  this  axis  from  tie 
extreme  point  of  tin  fold,  one  passes  over  successively  higher  and  higher  members  of  the 
coal-bearing  series  until  in  Twentymile  Park  the  uppermost  group  of  coal  beds  is  entered. 
These  in  turn  are  overlain  by  dark  clay  shale  distinct  in  character  from  the  rocks  of  the  coal- 
bearing  formation. 
The  major  syncline  just  described  is  interrupted  by  a  number  of  cross  folds  or  wrinkles. 
The  most  prominent  of  these  minor  folds  is  an  anticline  the  axis  of  which  follows  the  crests 
of  the  high  ridges  on  the  west  side  of  Twentymile  Park  and  crosses  Yampa  River  at  the 
mouth  of  Tow  Canyon.     On  the  north  side  of  the  river  the  axis  bends  a  little  west  of  north, 
a  This  paper  is  a  preliminary  report,  t<>  be  followed  later  by  one  giving  Culler  details  and  a  more  com- 
plete map. 
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