LIST OF FORMATIONS IX CENTRAL WYOMING 



40'i 



Period. 



Formation. 



Characteristics. 



Thick- 

 ness. 



IVIiocene 



Arikai'ee. 



Soft sandstone, gravel, con- 

 glomerate. 



Feet. 

 0-1,000 







Oligocene - 



Brule 



INIassive sandy clay, mostly 

 pale buff. 



0-400 



Chadron 



Sand, clay, and sandstone, 

 mostly light. 



0-100 



Eocene 



Bridger-Wasatch . 



Soft sandstone— red, gray, 

 green. 



1,000± 







Laramie, etcetera. 



Coarse buff to gray sand- 

 stone, gray shale. " 



1 

 1 



1- 4,000± 



1 



J 





Fox Hills-Mesa 

 Verde. 



Sandstone, local coal l)eds. . . 





Pierre 



Dark shale with concretions. 



3,000-1- 









Niobrara 



Limestone, chalk, and limy 

 shale, grading into shale 

 to northwest. 



100—150 



Cretaceous - 









Benton 



Gray shale ; buff sandstone 

 and concretions near top ; 

 hard shales (Mo wry beds) 

 near middle. 



800-1,200 









f Dakota 



Cleverly -j Fuson . 



i Lakota 



Buff sandstone 



r 50-150 





Gray to purple shale or clay. 

 Massive raff sandstone, con- 

 glomerate near l)ase. 



(?) 



Morrison 



Massive shale— pale green, 

 gray, maroon ; thin lime- 

 stone and sandstone. 



100-250 



Jurassic 



Sundance 



Soft buff sandstones ; green 

 shales with hard fossilifer- 

 ous layers. 



0-250 







Permian-Triassic (?) . 



Chugwater 



Red shale and soft red sand- 

 stone ; thin limestones, 

 and gypsum deposits. 



SOO-1 ,250 



r 



Embar 



Gray limestone, buff shale, 



cherty beds. 

 Massive, gray, cross-bedded 



sandstone. 

 Red shale overlain by shale. 



sandstone, and cherty 



limestone. 

 Limestone, light colored, 



massive near top. 



50-250 



Carboniferous -{ 



Tensleep * 



Amsden * 



iNIadison* 



;i0-300 

 100-300 



0-1,000 



Ordovician 



Bighorn 



Hard, massive, pale buff, 

 siliceous dolomite. 



0-150 









Cambrian (Middle)... 



Deadwood 



Brown sandstone, gray shale, 

 flat pebble Umestone con- 

 glomerate, and limestone. 



0-800 



Pre-Cambrian 



Granite, gneisses, 

 etcetera. 











» From tlie Casper niiise southward these three fcrmalioiiH give p nee to tlie Cnsper 

 5UII to l.iMHi feet thick, consisting of limestones genersilly lying on anjl overlain by gray 

 In the Laramie region and southward these rocks merge intoj-ed grits. 



foriimtion, 

 sandstone. 



