MILES   CITY   COAL  FIELD,   MONTANA.  39 
The  upland  areas  comprise  an  undulating  surface  at  elevations 
from  500  to  900  feet  above  the  main  drainage  levels.  Although  these 
plateaus  are  somewhat  uneven  and  in  places  are  broken  by  buttes  and 
canyons,  they  include  large  tracts  level  enough  for  cultivation,  but 
not  susceptible  to  irrigation  for  lack  of  available  water.  The  largest 
upland  area  southeast  of  Miles  City,  known  as  the  Pine  Hills  country, 
where  dry-land  farming  has  been  successfully  practiced  for  several 
years,  is  rather  thickly  settled. 
The  most  distinctive  topographic  features  of  this  region  are  its 
badlands,  which  almost  everywhere  surround  the  upland  areas  and 
form  a  ragged  fringe  separating  them  from  the  lowlands  of  the  val- 
leys. In  these  areas  the  topography  is  broken  into  intricate  detail. 
Drainage  is  maturely  developed  and  is  affected  by  a  multitude  of 
intermittent  watercourses  in  narrow  canyons,  which  conform  to  no 
general  system.  The  interstream  areas  are  eroded  into  sharp  peaks 
and  ridges  or  narrow  mesas  at  various  elevations.  In  general,  the 
individual  hills  and  spurs  or  topographic  units  are  comparatively 
small.  The  relief  from  canyon  to  hilltop  in  few  places  exceeds  200 
feet,  but  the  multitude  of  such  features  makes  the  badlands  exceed- 
ingly difficult  to  traverse  and  renders  them  unfit  for  anything  except 
grazing.  The  line  of  demarkation  between  the  lowland  and  the 
badland  areas  is  usually  distinct  and  definite,  the  badland  bluffs 
and  buttes  rising  abruptly  at  the  edges  of  the  valleys. 
In  many  places  along  Yellowstone  and  Powder  rivers  there  are 
broad  benches  or  terraces  from  100  to  250  feet  above  river  level. 
These  terraces  represent  former  valleys  of  the  streams  where  gravel, 
which  now  serves  as  a  protecting  cap,  was  deposited.  As  they  occur 
in  the  midst  of  the  badlands  they  are  rendered  conspicuous  by  the 
abrupt  change  of  topography.  The  terraces  are  too  high  above  the 
level  of  the  streams  to  be  irrigated,  but  they  are  valuable  for  their 
production  of  wild  hay,  and  may  become  more  valuable  for  dry- 
farming  purposes. 
A  noticeable  feature  of  the  region — one  which  adds  picturesque- 
ness  as  well  as  roughness  to  the  badlands — is  the  red  clinker  or  partly 
fused  and  baked  sand  and  clay  due  to  the  burning  of  coal  beds. 
Owing  to  the  superior  resistance  of  this  material  it  has  withstood 
the  processes  of  erosion  longer  than  surrounding  softer  rocks,  and 
is  thus  left  capping  buttes  and  ridges  and  fringing  the  outcrops  of 
unburned  coals. 
GEOLOGY. 
STRATIGRAPHY. 
Except  for  some  unimportant  alluvial  deposits  in  the  valleys  all 
the  rocks  exposed  in  this  district  are  of  Tertiary  age  and  belong  to 
a  formation  called  the  Fort  Union,  which  has  been  recognized  in  many 
