324  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1905. 
On  Third  Creek  lignite  appears  at  many  points.  About  4  miles  above  its  mouth,  ne 
the  McLellan  ranch,  in  sec.  4,  T.  136  N.,  K.  101  W.,  the  following  section  is  exposed: 
Section  of  lignite  at  McLellan  ranch,  on  Third  Creek. 
Ft.      in. 
Clay 20-100 
Lignite 8  6 
( !la  y 7-  8 
Lignite 9  2 
( flay  2  «) 
Lignite 3  6 
Unexposed  to  creek 7  0 
These  three  seams  outcrop  continuously  for  over  200  yards  and  have  a  slight  dip  to  tl 
east.  The  lowest  one  contains  thin  clay  layers,  hut  the  lignite  of  the  upper  beds  is  | 
excellent  quality.  Seven  or  eight  miles  south  of  this  point,  on  a  small  tributary  of  Sar 
Creek,  three  seams  <>f  lignite  occur  at  approximately  the  same  horizon  as  those  found  c 
Third  Creek  and  are  doubtless  to  be  correlated  with  them.     The  following  section  is  show) 
Section  of  lignite  near  Sand  Creek. 
Ft.  in. 
Clay 8-9 
Lignite 8 
Clay 2    0 
Lignite 8    9 
Clay 4 
Lignite (> 
Cla  y , 4    3 
Sandstone 1 
The  seams  exposed  in  the  above  section  have  burned  out  extensively,  and  the  red,  bun 
day  thus  formed  covers  large  areas  in  several  townships.     At  about  the  same  horizon  i 
this  burnt   clay   is  the  thick   lignite  seam  exposed  on  Sand  Creek  at   the   Russell  ranch  i 
sec.  31,  T.  135  N.,  k.  101   W.      The  section  shown  here  is  as  follows: 
Section  of  lignite  at  Russell  ranch  on  Sand  Creek. 
Ft.    in. 
(  lay 6-12 
Lignite 4      3 
Clay 2    10 
Lignite 33 
Clay,  to  creek  bed 4 
The  lignite  lies  quite  near  the  surface,  and  over  large  areas  it  has  been  eroded  by  San 
Creek  and  its  tributaries,  or  burned,  as  stated  above.  This  same  seam  appears  along  ti 
creels  from  one-fourth  to  one-half  mile  to  the  south,  and  probably  underlies  a  wide  are 
on  both  sides  of  Sand  Creek  Valley.  The  33-foot  seam  shown  in  the  above  section  is,  s 
far  as  known,  the  thickest  which  occurs  in  the  entire  lignite  region  of  North  Dakota  an 
Montana.  It  has  been  reported  to  have  a  thickness  of  40  feet,  but  careful  measuremer 
showed  it  to  be  33  feet,  though  if  the  upper  seam  and  the  clay  bed  between  are  include 
the  total  would  he  40  feet.  There  is  reason  to  believe  that  the  seams  outcropping  on  San 
Creek  are  to  be  correlated  both  with  those  exposed  7  or  8  miles  north  and  west  on  the  tril 
utary  of  the  same  creek  and  with  those  still  farther  north  on  Third  Creek.  If  this  corn 
lation  is  correct,  these  thick  seams  cover  an  area  at  least  15  miles  long  from  north  to  soul 
and  with  a  width  probably  as  great.  Other  beds  of  lignite  occur  at  several  points  fart  he 
south  on  Sand  Creek. 
