424 blackwelder: new formations in Wyoming 



A typical and centrally located section of this formation, to- 

 gether with the one next to be described, is exposed in the moun- 

 tains at the head of the Gros Ventre River and its tributaries, 

 especially north and east of Dorwin Peak. 



Chugivater formation 



Feet 

 23. Shale; brick red with thin gray laminae, resting on an ill-de- 

 fined and conformable bottom 10+ 



Diniooody formation 



22. Shale; grayish white, with ihin calcareous laminae, ripple- 

 marks and sun-cracks 80 



21. Dolomite and shale; thin-bedded, argillaceous dolomite inter- 

 bedded with gray shale and very thin quartzose flags. A 

 few Lingulas and small pelecypods 20 



20. Shale; calcareous, olive-gray rock with thin beds of dense gray 

 argillaceous dolomite. Some beds contain Lingulas, and 

 others pelecypods, too poorly preserved for identification. 51 



19. Flags and shale; alternating thin brittle beds of dolomite- 

 clay-quartz rocks of pale gray color, but weathering 

 tawny brown. Full of brownish Lingula shells 4 



18. Sandstone etc.; olive-gray calcareous sandstone, weathering 

 smoky brown and even black, owing to presence of man- 

 ganese oxides. Contain laminae and lenses of white chert, 

 occasionally more than a foot thick 20^ 



Park City formation 



17. Dolomite; light gray, siliceous, with fossils appearing as 

 silicified excrescences: Spiriferina pulchra, Derbya sp., 



Fenestelloid bryozoans 11^ 



16. Chert; alternating massive and shaly chert. The more mas- 

 sive beds have a peculiar tubular structure 35 



15. Shale and chert; black shale with thin laminae of black chert 



increasing toward the top 10 



14. Shale; coal black, slightly phosphatic and containing one 2- 



inch layer of back oolitic phosphorite 7 



13. Dolomite; black, but weathers drab. Saturated with hydro- 

 carbons 2^ 



12. Shale; black, slightly phosphatic shale 15 



11. Phosphorite; hard, black nodular bed, containing phospha- 



tizecl fossils. Has a stronger odor of hydrocarbons:^ 1 



Lingulodiscina missouriensis 

 Productus phosphaticus 

 Plagioglypta canna 

 Conularia sp. 



« Identified by Dr. G. H. Girty. 



