306  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1905. 
Feet. 
Coal - h 
Coaly  shale 2^ 
Coal 1 
Coaly  shale 2 
Coal 1 
Blue-green  clay 6 
Coal 1 
Dark  clay  and  shale. 
The  upper  beds  of  this  section  cross  Tongue  River  just  east  of  the  mouth  of  Early  Creek, 
where  the  coal  is  mined  in  small  amount.  The  thickness  of  the  bed  varies  from  5  to  6£  feet. 
This  coal  is  also  mined  to  some  extent  for  local  use  on  the  ridge  to  the  northwest. 
In  the  Clear  Creek  region  the  lignite-bearing  beds  of  the  De  Smet  formation  succeed  the 
Kingsbury  conglomerate  near  Buffalo  and  extend  eastward  with  a  width  of  about  18  miles 
on  Clear  Creek.  The  dips  are  to  the  northeast  at  angles  of  from  10°  to  20°  a  short  distance 
west  of  Buffalo,  but  the  amount  decreases  rapidly  to  the  east.  The  beds  comprise  5,000 
feet  or  more  of  alternating  shales  and  sandstones,  the  former  mostly  carbonaceous  and  the 
latter  soft  and  massive.  The  stratigraphy  is  variable,  and  no  regular  succession  of  beds 
could  be  established.  The  coal  occurs  in  local  beds  at  various  horizons,  and,  although  most 
of  the  deposits  appear  to  be  of  limited  extent,  a  large  amount  of  coal  is  available.  There 
are  four  principal  horizons  lying  near  together  a  few  hundred  feet  above  the  base  of  the  for- 
mation. In  the  region  northeast  and  east  of  Buffalo  part  of  the  coal  has  burned  out  near  the 
the  surface  and  the  heat  has  baked  the  adjoining  shales  into  red  clinkers  over  wide  areas. 
At  some  localities  the  coal  is  still  burning,  notably  at  an  abandoned  coal  mine  near  the 
southeast  corner  of  Lake  De  Smet. 
The  lowest  member  of  the  coal  measures  is  a  series  of  sandstones  lying  on  the  Kingsbury 
conglomerate  and  merging  upward  into  coaly  shale  which  extends  north  and  south  in  the 
region  north  and  west  of  Buffalo.  On  the  east  side  of  Rock  Creek,  in  the  northeast 
corner  of  T.  51,  R.  83,  it  is  6  feet  thick  and  contains  three  or  four  streaks  of  coal  of  poor 
quality.  The  principal  coal  deposits  of  the  Buffalo  region  occur  considerably  higher  in 
the  formation,  and  one  series  outcrops  along  a  zone  extending  from  the  southeast  corner 
of  Lake  De  Smet  to  the  mouth  of  Rock  Creek  and  thence  east  of  Buffalo.  Near  Lake  De 
Smet  the  old  mines  have  caved  in,  but  they  appear  to  have  worked  about  4  or  5  feet  of  coal. 
It  is  overlain  by  a  bed  of  clinkers.  Near  the  mouth  of  Rock  Creek,  at  the  Bodan  coal  mine, 
a  tunnel  has  been  run  in  on  a  12-foot  coal  bed  of  good  quality,  which  is  worked  to  a 
moderate  extent  every  winter.     The  section  at  this  place  is  as  follows: 
Section  at  Bodan  coal  mine,  near  Buffalo,  Wyo. 
Feet. 
Clinkers 6 
Yellow  sandy  clay,  with  G  feet  of  concretionary  sandstone  at  base HO 
Reddish-yellow  clay 4 
Dark  shale  with  plants 2 
Coal 12 
Light-gray  shale 2 
The  coal  appears  to  be  in  a  lens-shaped  deposit  and  thins  considerably  to  the  north  and 
south.  A  short  distance  north  an  8-inch  coal  bed  is  seen  underlying  the  clinker  bed.  A 
mile  east  of  the  Bodan  mine  and  at  a  somewhat  higher  horizon  is  the  old  Foot  mine,  in 
which  an  8-foot  bed  has  been  worked.  It  is  overlain  by  20  feet  of  light,  sandy  clay,  20  feet 
of  dark  shale  with  thin  coaly  streaks,  and  15  feet  of  yellow  sandy  clay.  This  coal  deposit 
is  on  fire  and  has  been  burning  for  several  years.  The  following  section  at  Monkers  & 
Mather's  mine,  a  mile  east  of  Buffalo,  shows  the  principal  succession  in  that  region.  The 
lower  7-foot  bed  is  probably  the  lowest  bed  of  importance  in  the  formation.  The  upper 
7-foot  bed  is  the  one  that  reaches  the  surface  near  the  mouth  of  Rock  Creek,  where,  as  above 
stated,  it  has  been  mined  at  several  places.  The  next  bed  lies  some  distance  above  and  is 
worked  at  the  Mitchell  mine,  2\  miles  east  of  Buffalo,  a  short  distance  below  the  lower 
clinker  bed.     It  is  6  to  8  feet  thick. 
