OF WESTERN NORTH AMERICA. 



53 



MIDDLE TO UPPER EOCENE (EUROPE, ETAGE BARTONIEN). 



6. LATER EOCENE DEPOSITS OF WASHAKIE BASIN; UINTATHERIUM AND EOBA- 



SILEUS ZONES. 



(Figs. 1, 2, 7; PL I.) 



HOMOTAXIS. 



North America. — 1, Uintatherium zone, equivalent to the upper part 

 of the Bridger formation and to the Uintatherium zone of Uinta 

 Basin. 2, Eohasileus zone, equivalent to the Eohasileus zone of 

 Uinta Basin. ?3, Deposits on Sage Creek, Montana. 



Euroi)e. — Bartonien of France. ' 



HISTORY. 



The Washakie Basin is a distinct area, with deposits mainly of 

 volcanic ash, in which Hayden (1867-1869) first used Washakie as 

 a group name comprising the 

 lower and middle Eocene sec- 

 tion. Subsequently he inclined 

 to the belief" ^'that the upper 

 series is either an extension east- 

 ward of the Bridger group or 

 synchronous with it." It was 

 similarly referred to by King as 

 the Bridger group of the Washa- 

 kie Basin. ^ This upper series 

 has sometimes been referred to 

 in paleontologic literature as the 

 Washakie formation." 



FAUNA.^ 





Z 









< 









OQ 







B 

 250' 



KIE 





Eobasilevts 



WASHA 





zone 





OF 









U 



z 

 u 





4 Uintathe- 



A 

 250' 



:oc 





^ rium 



cc 





~=\ zone 





UJ 



h 

 < 









-I 





Dolichorhinus 

 Amynodon 

 Achaenodon 

 Eohasileus 



Manteoceras 



Mesatirhlnus 



Uintatherium 



liG. 7.— Preliminary columnar section of the later 

 Eocene deposits of Washakie Basin, Wyoming. 

 The upper or Eohasileus zone is now (1908) deter- 

 TP /. 1 • mined as thicker than the lower division. 



ihe mammahan fauna of this 

 stage, which has long been recognized (Osborn,"^ 1881) as in general 

 intermediate between the Bridger and the Uinta, is sparsely known. 

 The American Museum expedition (Osborn, Granger) of 1906 very 

 precisely fixed its age as overlapping the summit of the Bridger and 

 the Uintatherium and Eohasileus zones of the Uinta Basin. 



Faunal divisions. — (A) Uintatherium zone. Brown beds (250 feet) 

 containing Uintatherium. Among Perissodactyla, Mesatirhinus mega- 



aPrel. Rept. U. S. Geol. Survey Terr., 1871, p. 73. 



b King, Clarence, U. S. Geol. Explor. 40th Par., Systematic geology, 1878, p. 390. 

 c See Appendix, p. 91. 



d A memoir upon LoTolophodon and Uintatherium: Contr. E. M. Mus. Geol. Archseo!. Princeton, 

 vol. 1, No. 1, 1881, pp. 1-14. 



McMaster, John Bach, Stratigraphical report upon the Bridger beds in the Washakie Basin, 

 Wyoming Territory, accompanied by profiles of three sections, in Osljorn, H. F., A memoir, etc., as 

 above. 



