ILLUSTRATIONS. 



Page. 



Plate I. Map of the United States, showing general Mountain and Great Plains 

 regions, also location of the principal formations, sections, and 



deposits considered in this paper 7 



II. Oligocene and Miocene exposures in South Dakota, northwestern 



Nebraska, and eastern Wyoming 60 



III. Idealized bird's-eye view of the gi'eat Badlands of South Dakota, 

 showing channel and overflow deposits in the Oligocene and lower 



Pliocene 64 



Fig. 1. Composite section of the Tertiary deposits of the West 23 



2. Map of southwestern Wyoming and northern Utah, showing partial 



areas of the Wasatch, Wind River, Bridger, and Uinta formations. ... 37 



3. Composite columnar section of the Wasatch formation of Bighorn Basin. . 38 



4. Columnar section showing the relations of the typical Wasatch section, 



including the Knight formation, to the overlying and underlying 

 formations 39 



5. Columnar section of the Wind River basin, based on the descriptions 



of Hayden and Loomis 44 



6. Columnar section of the Bridger formation, Henrys Fork, western 



Wyoming 51 



7 . Preliminary columnar section of the " " V\'ashakie formation, ' ' Wyoming ... 53 



8. Columnar section of the Uinta formation, northern Utah 55 



9. Diagrammatic section of the ^\Tiite River group. South Dakota 62 



10. Pro^isional correlation of some of the chief epicontinental Oligocene- 



Pleistocene deposits and formations of the V\'est in which fossil mam- 

 mals have been recorded 65 



11. Columnar section of the John Day formation, Oregon 67 



12. Columnar section of the Rosebud formation 70 



13. Columnar section of the Gering, Monroe ( reek, and Harrison formations, 



western Nebraska 72 



14. Diagrammatic section of the Gering, Monroe Creek, and Harrison forma- 



tions, western Nebraska 73 



15. Diagrammatic section of the Staked Plains (Llano Estacado), Texas, 



showing the relations of the "Clarendon," "Rock Creek," and 

 Blanco to the underlying ' ' Panhandle . 82 



6 



