20  CONTRIBUTIONS   TO   ECONOMIC    GEOLOGY,  1907,   PART   II. 
It  will  be  noted  that  although  there  are  twenty  beds  of  lignite  in 
the  foregoing  section,  none  of  them  is  workable,  the  thickest  being  30 
inches.  But  the  thick  lignite  bed  which  outcrops  less  than  2  miles 
above  and  below  the  point  where  the  section  was  measured  can  not 
here  be  far  below  river  level. 
The  following  section  was  measured  in  the  NE.  J  sec.  4,  T.  142  N., 
R.  101  W.,  3  miles  east  of  the  one  just  given,  and  lies  wholly  in  the 
upper  division  of  the  Fort  Union,  its  base  resting  on  top  of  the  lower 
member: 
Section  3\  miles  east  of  Short's  ranch,  in  the  NE.  |  sec.  4,  T.  142  N.,  R.  101  W. 
Ft.     in. 
Sand  and  clay  in  alternating  layers,  more  argillaceous  at  the  base.  80 
Lignite  band,  thin. 
Clay,  sandy 10 
Clay,  bituminous 2 
Clay,  sandy 10 
Powdery  material,  probably  weathered,  shaly  lignite. 
Clay,  gray,  forming  when  wet  a  sticky  mud ,  sandy  near  middle . .  25 
Lignite  in  two  beds,  the  upper  1  foot  and  the  lower  1^  feet, 
separated  by  4  inches  of  brown  shale 2     10 
Clay,  gray,  with  hard,  concretion-like  masses  of  same  color 55 
Lignite 2 
Clay,  gray,  sandy 10 
Lignite 1 
Clay,  gray,  sandy,  more  clayey  above  and  below 50 
Lignite 3      6 
Sand  and  sandy  clay,  gray,  rather  coarse  sand  near  center,  fine 
grained  at  top  and  bottom,  with  yellow  bands 55 
Lignite 1 
Sand,  clayey,  bluish  gray,  contains  irregular  ironstone  bands, 
rather  coarse  sand  at  base,  but  grows  gradually  finer  till  at  top 
it  is  a  clay 40 
Lignite,  poor!  f  1      3 
Clay,  gray  . .  iBed  F,  Sentinel  Butte  group j  7 
Lignite,  poor  J  [  3 
358      7 
The  beds  of  the  upper  division  of  the  Fort  Union  are  found  in 
Sentinel  Butte,  and  the  following  section  was  measured  there : 
Section  at  Sentinel  Butte. 
Ft.    in. 
Clay,  calcareous 10 
Limestone,  alternating  with  calcareous  clay;  the  limestone  is 
very  compact  and  fine  grained,  brittle,  siliceous,  and  gray  and 
white  in  color,  weathering  into  very  thin  laminae;  contains  fish 
remains 5 
Clay,  gray,  very  calcareous,  weathering  to  greenish 25 
Sandstone,  gray,  hard 80 
Clay,  gray  and  yellow,  sandy 30 
Clay,  brown,  with  thin  seam  of  lignite 1    6 
