MINERAL    RESOURCES    OF    BIGHORN    BASIN.  318 
(season  deposits  of  this  variety  of  clay  were  discovered  in  the  lower  part  of  the  Laramie 
I  formation,  also  in  the  overlying  Wasatch  formation.  Those  in  the  Laramie  formation  are 
I  associated  with  thin  deposits  of  coal  and  coaly  shale  in  a  series  of  sandy  beds  outcropping 
:  at  the  head  of  Bud  Kimball  Draw,  12  miles  southeast  of  Tensleep,  Wyo.  A  section  of  the 
;  deposit  is  here  given: 
Section  of  bentonite  deposit  at  head  of  Bud  Kimball  Draw,  Wyoming. 
Ft.   in. 
Coal  and  brown  leaf-bearing  shale  in  alternate  layers 2 
Dark-gray  sandy  clay 5 
Bentonite  clay , 3 
Dark  leaf-bearing  shale 6 
Bentonite  clay f. 3 
Light-gray  clay 3 
Dark-gray  sandy  clay 3 
Gray  sandstone 1      6 
Impure  coal 10 
Gray  sandstone. 
In  the  bad  lands  of  the  Wasatch  formation,  on  the  south  side  of  Cottonwood  Creek,  about 
10  miles  southeast  of  Meeteetse,  an  impure  bentonite  occurs. 
GYPSUM. 
The  gypsum  deposits  of  the  Bighorn  Basin  are  mainly  in  the  Chugwater  formation.  They 
occur  also  in  the  lower  part  of  the  Sundance  formation  and,  at  one  locality,  a  deposit  8  feet 
thick  was  observed  in  the  upper  part  of  the  Morrison  formation.  In  the  Chugwater  red  beds 
there  is  usually  a  gypsum  layer  30  to  40  feet  thick  near  the  top  of  the  formation  and  gener- 
ally one  of  equal  thickness  at  or  near  its  base.  Along  the  south  side  of  the  basin  the  gypsum 
at  the  base  of  the  red  beds  is  absent.  Thinner  beds  of  gypsum  are  found  at  various  hori- 
zons in  the  Chugwater  formation,  but  these  appear  to  be  of  local  deposition.  In  most 
places  where  the  gypsum  has  been  carefully  examined  it  is  apparently  of  good  quality, 
though  no  analyses  have  been  made  to  determine  its  exact  chemical  nature.  It  is  white, 
compact,  and  massive,  and  generally  occurs  in  beds  that  are  free  from  partings.  The  fol- 
lowing section,  taken  on  Trail  Creek  northwest  of  Cody,  will  show  the  position  of  the  gypsum 
in  the  upper  fat  of  the  Chugwater  red  beds: 
Section  of  a  portion  of  the  Sundance  and  underlying  Chugwater  formations  on  Trail  Creek, 
Wyoming. 
Feet. 
Green  shale  containing  thin  limestone  layers  (Sundance) Zh, 
Red  sandy  shale  containing  thin  layers  of  gypsum  (Chugwater) 12 
White  massive  gypsum 30 
Red  sandstones  ("Red  Beds"). 
About  10  miles  south  of  Cody  a  deposit  of  gypsum  was  observed  in  the  upper  part  of  the 
Morrison  formation.     The  following  section  shows  its  relative  position: 
Section  of  a  portion  of  the  Morrison  and  overlying  Cloverly  formations  south  of  Cody,  Wyo. 
Feet. 
Brown,  coarse-grained,  cross-bedded  sandstone  (Cloverly) 60 
Reddish  sandy  shale  with  thin  gypsum  layers 25 
White  massive  gypsum 8 
Reddish  sandy  shale  with  thin  gypsum  layers 15 
Though  there  are  extensive  deposits  of  gypsum  throughout  this  area,  no  attempt  has 
been  made  to  utilize  the  product,  except  in  a  very  small  way.  At  a  stucco  mill  about  10 
miles  northeast  of  Windsor  post-office,  Wyo.,  across  the  Montana  line,  plaster  is  manu- 
factured from  a  gypsum  deposit  near  the  base  of  the  Chugwater  red  beds.     The  beds  mined 
