56 



GUIDEBOOK OF THE WESTERT^J" UT^ITED STATES. 



Successio7i and character of the for 7)10110773 exposed in the Han77a coalfield^ hetween Cottio 



and Fort Steele, Wi/o. ^ 



System. 



Formation. 



Tertiary 

 (possibly 



iiicludes 

 Bome Cre- 

 taceous). 



a 



Thick- 

 ness (feet) 



Upper Lar- 

 amie 

 mation. 



" fur- 



10, 000? 



''Lower 



Laramie" 

 formation. 



6,200+ 



Cretar-eous, 



Lewis sluile. 3,200+ 



Mesaverde 



formation. 



2,700 



Steele shale 



3,000+ 



Character. 



Alternating beds of shale 

 and sandstone, of drab, 

 gray, and yellow col- 

 ors. The sandstone is 

 conglomeratic -at the 

 base and in a zone 

 about 7,000 feet above 



the base. The peb- 

 bles of these conglom- 

 erates represent older 

 rocks, now exposed in 

 the mountains sur- 

 rounding the basin. 

 The formation 

 tains 



con- 

 well-preserved 



fossil plants, shells of 

 fi'esli-water animals, 



and in the lower part, 

 bones of huge dino- 

 saurs. 



Drab and gray shale, al- 

 ternating with brown 

 to gray sandstone. 

 Fossil plants, shells of 

 fresh and brackish 

 water invertebrates 

 (also marine shells in 

 the lower part), and 

 bones of turtles, dino- 

 saurs, and other ani- 

 mala occur in these 

 rocks. 



Dark-gray shale with 

 intercalated sandy 

 beds. The fossils in 

 this formation consist 

 entirely of marine 

 shells. 



White to brown sand- 

 stone and drab diale. 

 Marine shells and the 

 marine plant Ilaly- 

 meniles major occur in 

 the lower part, and 

 fresh and brackish 

 water shells in the 

 upper part. 





Drab shale and tliin beds 

 of^ sandstone. Con- 

 tains marine foasils; 

 ridge - making sand- 

 stone layers near the 

 top. 



Eeonomio features. 



The most produc- 

 tive coal formation 

 in this coal field. 

 The coal beds are 

 in places 30 feet in 

 thickness but are 



commonlY from 5 

 to 10 feet thick. 



Contains several tliin 

 irregular beds of 

 coal, but none of 

 them are now 

 mined. 



Contains a few thin 

 irregular coal beds 

 of little economic 



value. 



