296         CONTRIBUTIONS   TO   ECONOMIC   GEOLOGY,   1907,   PAET   II. 
POST-LARAMIE    COAL. 
Nomenclature  and  stratigraphic  position. — -A  considerable  group  of 
workable  coals  is  found  in  the  formation  unconf ormably  overlying 
the  Laramie.  On  account  of  the  uncertainty  as  to  whether  these 
beds  should  be  called  Fort  Union  and  classed  as  a  part  of  the  Ter- 
tiary system  or  form  an  upper  and  unconformable  part  of  the 
Cretaceous  system,  the  coals  are  for  the  present  referred  to  as  post- 
Laramie,  as  they  constitute  the  only  recognized  coal  group  overlying 
the  Laramie  formation  in  this  field.  The  zone  containing  the  work- 
able coals  is  in  the  lower  part  of  these  later  beds.  The  principal  coal 
group  appears  to  be  in  a  zone  400  to  500  feet  above  the  basal  con- 
glomerate member  already  described  as  marking  the  unconformity  at 
the  top  of  the  Laramie. 
Distribution  of  post-Laramie  coal-bearing  strata. — The  coal-bearing 
beds  immediately  succeeding  and  overlying  the  Laramie  in  the  Yampa 
field  outcrop  in  a  belt  of  hills  and  ridges  north  of  the  Laramie  district. 
They  extend  continuously  westward  from  the  vicinity  of  Cedar  Moun- 
tain as  far  as  and  probably  beyond  Maybell,  but  beyond  Sand  Creek 
they  are  concealed  by  the  unconformable  " Browns  Park"  beds. 
Local  development  of  the  coal. — West  of  Cedar  Mountain  these  coals 
are  found  near  Ducey's  ranch,  in  the  northeast  corner  of  T.  7  N., 
R.  92  W.,  where  a  local  bank  has  been  opened  on  one  of  the  beds  in 
the  NW.  \  sec.  2.  The  coal  exposed  at  the  entry  is  7  feet  2  inches 
thick  and  is  overlain  by  soft  clay  or  shale;  about  2\  feet  of  the  top 
of  the  coal  has  been  left  as  roof.  West  of  this  point  the  coal  may 
be  readily  traced  by  numerous  outcrops  through  T.  8  N.,  Rs.  92  and 
93  W.,  and  T.  7  N.,  Rs.  94  and  95  W. 
In  the  valley  of  Lay  Creek  one  of  the  beds  of  this  group  has  been 
worked  for  local  use  at  the  Blevins  mine,  in  the  NW.  \  sec.  28,  T. 
8  N.,  R.  93  W.  The  coal  at  the  Blevins  mine  appears  to  be  fairly 
representative  of  most  of  the  coals  of  this  group.  The  bed  is  1 1  feet 
4  inches  thick,  and  all  of  it  is  taken  out  in  the  entry,  together  with 
about  5  inches  of  laminated  blue  clay  at  the  top.  Above  the  clay  is 
a  massive,  coarse-grained  white  sandstone  forming  a  solid  roof  at 
least  40  feet  thick.  The  beds  dip  4°  N.  5°  E.  The  coal  bed  is  with- 
out seam  or  parting.  The  floor  is  covered  by  4  or  5  inches  of  bony 
coal,  below  which  is  a  solid  white  sandstone.  There  are  no  signs  of 
burning  of  the  outcrops  in  this  immediate  vicinity;  in  fact,  the  coals 
of  this  group  seem  less  subject  to  combustion. at  the  outcrops  than 
the  older  coals. 
Some  of  the  post-Laramie  coals  are  also  opened  in  Spring  Creek 
Gulch,  in  T.  7  N.,  R.  95  W.,  where  several  local  banks  have  been 
worked  at  various  times. 
Character  of  the  post-Laramie  coal. — The  coal  breaks  down  at  the 
face  of  the  Blevins  mine  very  easily  when  loosened,  but  is  very  tough 
