SENTINEL   BUTTE   LIGNITE   FIELD,   N.   DAK.   AND   MONT. 
Ft.    in. 
Clay,  brown  and  carbonaceous 8 
Sand,  with  some  clay 6 
Clay 4 
Lignite 8 
Clay,  gray 1    6 
Lignite 1 
Clay,  gray  and  yellow 3 
Sand,  gray,  fine 8 
Lignite .• 2    6 
Clay,  blue 7    6 
Lignite 1    £ 
Clay,  blue,  plastic 5    6 
Lignite,  with  6-inch  clay  parting  3  inches  above  bottom 2    6 
Clay,  blue,  plastic 3    6 
Lignite 5 
Clay,  blue,  plastic 3 
Lignite 9 
Clay,  blue 3 
Sand,  yellow  and  gray,  fine  grained  and  laminated 4 
Lignite 1 
Clay,  gray 6 
Lignite,  with  1-inch  parting 9 
Clay,  bluish  gray 4 
Clay,  gray  and  brown,  with  a  thin  streak  of  lignite 4 
Sand,  yellow  and  gray 3 
Clay,  light  gray,  growing  sandy  above - 1    4 
Clay,  brown 4 
Lignite 1    6 
Clay,  light  gray,  with  thin  streak  of  lignite 1     1 
Sand,  gray 3 
Clay,  blue  and  yellow 8 
Sand,  yellow  and  gray 4 
Clay,  sandy  and  finely  laminated 1    4 
Clay,  blue 3 
Lignite 3 
Clay '.  7 
Lignite 6 
Sand ,  growing  clayey  above 2 
Clay,  bluish  gray,  with  thin  streak  of  lignite 6 
Sand,  gray 5 
Lignite 1    2 
Clay,  sandy,  yellow 6 
Lignite,  with  some  brown  clay 4 
Clay,  sandy  and  laminated  toward  top 14 
Lignite 
Clay,  gray : 3    6 
Lignite  and  brown  clay 1 
Sand ,  gray,  fine 1     6 
Clay,  gray 2 
Clay,  brown,  with  2  to  4  inches  of  lignite  at  base 
Clay,  light  gray 2    8 
Sand,  gray,  fine  grained,  with  hard  ledge  of  rock  near  top;  exposed 
above  river • ' 
288    3 
