240  CONTRIBUTIONS    TO   ECONOMIC    GEOLOGY,  11)06,  PART    I. 
southward  to  Denver.  The  map  (fig.  8)  shows  that  the  area,  to 
which  a  Portland  cement  plant  in  this  portion  of  Wyoming  woull 
ship  its  product  includes  eastern  Wyoming,  western  Nebraska,  north] 
eastern  Colorado,  and  a  part  of  northwestern  Kansas. 
TOPOGRAPHY    AND    GEOLOGY. 
Solid  rocks  are  not  exposed  in  the  immediate  vicinity  of  Cheyenne, 
hut  along  the  east  edge  of  the  Laramie  Front  Range  there  is  practicalli 
the  same  succession  of  Paleozoic  and  Mesozoic  rocks  that  occurs  in  the 
Black  Hills.  These  old  rocks  are  crossed  by  the  Colorado  and  South! 
ern  Railroad  at  two  points,  and  were  examined  by  the  writer  at  Iron 
Mountain  station,  about  in  miles  from  Cheyenne.  At  Iron  Mountain 
the  rocks  are  tilted  steeply  to  the  east  and  the  mountain  front   is  in 
i 
Portland-cement  pldnts 
l- ig.  8.     Map  showing  location  of  Cheyenne  and  Newcastle,  Wyo.,  in  relation  to  established  Portlanl 
(•'•mi 'i it  plants  and  1  r.niMMiii  incut,! I  railroads. 
consequence  marked  by  rugged  hogbacks  and  valley-,  formed  respec- 
tively on  resistant  sandstone  beds  and  soft  shales.  The  strata  in 
general  strike  north-south  and  dip  eastward  at  an  angle  of  about  70. 1 
RAW    MATERIALS. 
The  formations  sampled  in  the  vicinity  of  Iron  Mountain  include 
limestones  from  the  Niobrara  formation  and  the  Minnekahta  lime- 
stone, and  shales  from  the  Graneros  formation  and  the  Pierre  shale. 
LIMESTONE. 
.  Niobrara  formation. — The  best  lime-tone  sampled  is  from  a  hill  of 
Niobrara  which  lies  east  of  the  end  of  the  Bradley  spur,  across  a  nar- 
row flat.  It  is  a  thin-bedded  shaly  white  limestone  and  is  here  and 
there  fossiliferous.     The  rock  shows  at  man}'  places  small  yellowish! 
