246  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,    1907,   PART   II. 
Generalized  section  of  coal-bearing  rocks  in  western  portion  of  the  Little  Snalcc  River 
coalfield,  Wyoming. 
Economic  designa- 
tion. 
Description. 
Thickness  in 
feet. 
Sys- 
tem. 
Formation. 
North 
end  of 
field. 
South 
end  of 
field. 
Upper   part   of   Wa- 
satch and  later  Ter- 
tiary. 
Variegated  clay,  passing  up- 
ward into  brown  and  gray 
shales,     sands,     and     sand- 
stones.   Not  coal  bearing. 
Top  not  seen. 
^ 
Wasatch. 
Upper  coal  group. 
Shale  and  soft  sandstone,  with 
many  beds  of  impure  coal. 
Conglomerate. 
Gray  and  brown  sandstones 
and  gray  and  drab  shales, 
with  many  coal  beds. 
White  to  dark  clay  shale.     No 
coal. 
Heavy  sandstone,  with  inter- 
bedded  shale  and  numerous 
beds     of    good     coal;  con- 
glomerate at  the  base. 
8,500 
o3 
t 
^ — ^~     (?) 
(?)« 
Oto 
4,000 
Laramie  formation.6 
Middle  coal  group. 
Brown  and  gray   shaly  and 
concretionary      sandstones 
and  dark  shale,  with  several 
beds  of  coal.    In  the  south- 
ern end  of  the  field  the  lower 
half  is    yellow,   softer,  and 
more  sandy  and  apparently 
contains   little  coal.       Ma- 
rine fossils  in  base. 
4,000 
Oto 
2,500 
si 
s 
o 
bo 
a 
PI 
O 
3 
Lewis  shale. 
Drab,  slightly  sandy,  highly 
gypsiferous  shale,  with  a  few 
thin,  soft  sandstones.     Not 
coal  bearing. 
1,600 
2,300(?) 
O 
Mesaverde  forma- 
tion. 
Lower  coal  group. 
Upper  and  lower  members  con- 
sist of  heavy  sandstone  with 
a   few   interbedded    shales. 
Intermediate  member  con- 
sists of  shaly  sandstone  and 
shale.    Upper  member  coal 
bearing. 
2,500 
Bottom 
not 
seen. 
Dark     drab,     concretionary, 
calcareous  shale, with  several 
thin,     soft,     brown     sand- 
stones.   Not  coal  bearing. 
Botton 
not  seen. 
a  The  three  lower  members  of  the  upper  coal  group  have  the  stratigraphic  position  of  the  "Upper 
Laramie"  of  A.  C.  Veatch,  Coal  fields  of  east-central  Carbon  County,  Wyo.:  Bull.U.  S.  Geol.  Survey  No. 
316,  1907,  pp.  244-2G0. 
b  This  formation  is  the  equivalent  of  the  ' '  Lower  Laramie"  of  the  report  noted  above. 
SHALE. 
The  shale  which  underlies  the  lower  coal  group  is  equivalent  to  the 
upper  part  of  the  Mancos  shale,  as  that  formation  has  been  described 
and  mapped  in  western  Colorado.  The  shale  is  dark  drab  in  color, 
somewhat  concretionary,  and  very  calcareous,  and  contains  numerous 
thin,  soft  brown  sandstones,  especially  near  the  top.  The  shale  is 
not  coal  bearing. 
MESAVERDE    FORMATION. 
The  full  thickness  of  the  Mesaverde  or  lower  coal  group  was  studied 
only  in  the  north  end  of  the  field.  Where  observed  the  basal  third 
of  the  formation  consists  of  light-colored,  massive  sandstone,  much 
