THE CRETACEOUS PERIOD. 



157 



• West Elk breccia 



Ruby formation 



Ohio formation 



Laramie series . 



Montana series 



Colorado series 



Dakota formation 



Jura-Trias 



Maroon 



conglomerate 



Weber limestone 



Mississippian 



Ordovician 



Cambrian 



Archean 



tt 



bfl£ 



3'C 



Pleistocene 



Bozeman series 



Sphinx conglom- 

 erate 



Livingston series 



r 



I 



Laramie series i 



I 



I 



Montana series 



Colorado series 



Dakota formation 



Ellis formation 



Quadrant forma- 

 tion 





Madison limestone J 



.so 



e& 



m °>£ 



gs 



— ^ 



- — 



o 



°§ 



la 





3~ 



1 = 



c.2 

 O -5 



■P'S 



o 



— .- — — sa o 



C b£ 



'P 



IB «3 



