130         CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,    1907,    PART   II. 
coals  Nos.  1  and  2  make  bluffs  along  Goose  Creek  north  of  Dietz  and 
on  Tongue  River  east  of  Goose  Creek. 
A  sixth  coal  bed  in  the  Tongue  River  group  is  exposed  210  to  215 
feet  above  Dietz  bed  No.  1,  in  the  hills  south  of  Dietz,  where  it  is 
mined  for  local  use.  The  coal  here  is  nearly  5  feet  thick  and  is 
referred  to  as  the  Smith  coal,  from  the  name  of  the  operator  of  the 
local  mine.  A  massive  white  sandstone  20  feet  thick  underlies  the 
blue-shale  floor  of  the  coal.  The  outcrop  of  the  sandstone  makes  a 
white  band  and  is  a  marked  feature  of  the  hills  both  northeast  and 
south  of  Dietz.  The  rocks  are  chiefly  shale  from  this  white  sandstone 
down  to  Dietz  coal  No.  1. 
The  uppermost  bed  at  present  known  of  the  Tongue  River  coal 
group  occurs  125  feet  above  the  Smith  coal,  and  is  separated  from  it 
by  shale  with  a  few  thin  sandstone  beds.  This  coal  bed  has  been 
prospected  and  mined  for  local  consumption  2  miles  northeast  of 
Dietz  by  Mr.  Roland,  and  may  be  known  for  purposes  of  description 
as  the  Roland  coal.  The  bed  at  this  locality  is  13  feet  thick.  Be- 
tween Dietz  and  Sheridan  the  Roland  coal  bed  is  believed  to  be 
replaced  by  a  thick  bed  of  bituminous  shale,  with  bands  of  bony  coal 
2  feet  and  less  in  thickness  in  its  midst. 
Intermediate  coal  group. — From  the  Roland  coal,  which  marks  the  top 
of  the  Tongue  River  coal  group,  upward  700  feet  the  rocks  are  com- 
posed chiefly  of  shale.  Here  and  there  are  thin  strata  of  white  to 
brown  sandstone.  Bands  of  carbonaceous  shale  are  of  common 
occurrence,  and  there  are  several  beds  of  coal  that  are  evidently 
limited  to  small  areas.  Continuing  upward  there  are  450  to  470  feet 
of  shale  and  sandstone  in  alternating  strata,  each  kind  of  rock  being 
nearly  equal  to  the  other  in  aggregate  thickness.  A  number  of  car- 
bonaceous shale  beds  10  to  20  feet  thick  were  noted,  with  a  few  beds 
of  coal  of  workable  thickness  though  of  small  areal  extent. 
Ulm  coal  group. — Two  workable  beds  of  coal  of  considerable  areal 
extent  occur  in  the  rock  section  1,100  to  1,200  feet  above  the  top  of 
the  Tongue  River  coal  group.  Over  the  larger  part  of  the  Sheridan 
field  these  upper  coal  beds  have  been  removed  by  erosion.  Their 
remnants  are  found  in  the  south-central  part  of  the  mapped  area,  near 
the  top  of  the  watershed  between  Tongue  River  and  Clear  Creek. 
These  two  coal  beds  are  termed  for  convenience  the  Ulm  coal  group, 
because  of  their  best  known  occurrence  in  the  vicinity  of  Ulm, 
on  the  Burlington  Railroad.  They  are  separated  by  about  100  feet 
of  shale  and  soft  sandstone  beds  similar  to  the  sandstone  and  shale 
lying  below.  The  Ulm  coal  beds  vary  both  in  section  and  thickness. 
Exposures  of  these  beds,  however,  are  rare  on  account  of  the  exten- 
sive burning  they  have  suffered  near  the  surface.  Both  beds  are 
broken  .by  shale  partings,  usually  into  two  or  more  benches,  but  the 
total  coal  in  each  is  ample  for  mining.     Above  these  two  coal  beds 
