259 
GEOLOGY. 
STRATIGRAPHY. 
OUTLINE    OF    GEOLOGIC    SUCCESSION. 
The  present  investigation  led  to  the  conclusion  that  the  subdi- 
visions previously  mapped  by  King  and  Powell  could  not  be  applied 
to  the  sequence  of  rock  in  this  region.  The  fossils  collected  by  this 
party  and  studied  by  F.  H.  Knowlton  and  T.  W.  Stanton  indicate 
that  the  several  formations  have  the  geologic  time  values  indicated 
in  the  accompanying  table,  where  the  general  character  and  suc- 
cession of  the  Cretaceous  and  Tertiary  rocks,  together  with  their 
economic  importance,  are  set  forth. 
Section  of  Cretaceous  and  Tertiary  rocks  of  Sweetwater  County,  Wyo. 
Formation. 
Green  River. 
Unconformity. 
Green  River. 
Unconformity. 
"Wasatch. « 
Unconformity 
Laramie  (?) 
R   • 
Economic 
£1 
designa- 
&& 
tion. 
■3-s 
& 
350 
GOO 
400 
to 
825 
Black 
Rock- 
1,200 
to 
2,650 
coal 
group. 
Black 
Buttes 
coal 
±2,371 
group. 
Description. 
Massive     irregular 
sandstone. 
bedded 
Thin-bedded  shales,  sand- 
stones, and  limestones,  some 
of  which  are  oolitic,  for  the 
most  part  light  colored, 
white,  gray,  yellow,  or 
greenish. 
Variegated  clays,  shales,  and 
sandstones,  the  sandstones 
in  places  being  slightly  con- 
glomeratic. 
Alternating  layers  of  white, 
yellow,  and  brown  sand- 
stones, gray,  drab,  and  car- 
bonaceous shales,  with  coal 
beds  and  conglomerate  con- 
taining granite  and  quartz- 
ite  pebbles.  Numerous 
1  lands  of  white  concretion- 
ary sandstone  weathering 
in  irregular  shapes.  Basal 
sandstone  is  conglomeratic. 
Massive  basal  bed  of  white 
and  yellow  sandstones, 
showing  traces  of  conglom- 
erates places;  tonus  prom- 
inent scarp.  The  overlj  ■ 
Ing  bed  consists  of  variable 
sandstones,  clay,  and  coal 
beds.  Fossils  abound  in 
places. 
Economic  value. 
Most  important  spring 
horizon.  Contains 
some  coal. 
Prolincally  coal  bearing. 
Many  thin  beds  of  coal,  and 
at  least  one  bed  25  feet 
thick  occurs  in  this  group. 
No  mines  working  this 
coal.  One  prospect  east 
of  Hallville.  Coal  mined 
for  ranch  use  at,  Hooton's 
prospect,  T.  23  N.,  R. 
104  E.  Yields  artesian 
water.  Flowing  well  at 
Bitter  Creek. 
Coal  bearing. 
Numerous  important  beds. 
Old  mine  opened  and 
worked  on  these  beds 
near  Black  Buttes  sta- 
tion. New  mine  opened 
In  1907  south  of  Black 
Unites.    Prospects  a1  \  a- 
rious  points.     May  J  [eld 
artesian  water. 
«  Abundant  collections  of  plants  have  been  obtained  from  the  lower  third  of  this  formation  and  deter- 
mined by  F.  II.  Knowlton,  who  studied  the  collection,  as  undoubtedly  Fort  Union. 
