PORTLAND    CEMENT    MATERIALS    IN    EASTERN    WYOMING.       233 
includes  northwestern  Wyoming,  the  Black  Hills  in  South  Dakota, 
northwestern  Nebraska,  and  all  of  Montana.     (See  fig.  8,  p.  240.) 
hafe 
Morrison  shale 
Gypsum 
:.., 
Spear-fish 
formation 
Mmnekahta 
limestone 
Formations  not 
known  to  contain 
raw  material  for 
Portland  cement 
Localities  at  which 
rocks  were  sampled 
Fig.  7.— Map  showing  distrihution  of  Portland  cement  raw  materials  in  vicinity  of  Newcastle,  Wyo. 
Generalized  from  geologic  map  in  Newcastle  folio,  by  N.  II.  Darton. 
TOPOGRAPHY  AND  GEOLOGY. 
North  and  east  of  Newcastle,  toward  the  Black  Hills,  lies  a  highly 
dissected  plain  that  rises  toward  the  north,  the  geology  of  which  has 
been  described  by  N.  H.  Darton  in  the  Newcastle  folio. a     Within 
Geologic  Atlas  U.  S.,  folio  107,  U.  S.  Geol.  Survey. 
