352 C. Deperet — Oligocene of the Roanne Basin. 



Table of Mid- Tertiary Correlatives. 



European Stages 



Nebraska Section 



John Day Basin 



Upper and Middle 

 Miocene 



Lower Miocene 

 (Aquitanian) 



Upper Harrison beds 



Lower Harrison beds 

 Monroe Creek beds 

 Gering sandstone 



Mascall formation and 



Columbia Lava 

 [Interval of erosion] 

 Upper John Day beds 

 Middle John Day beds 



Upper Oligocene 

 (Stampian) 



Lower Oligocene 

 (Sannoisian) 



Leptanchenia beds and 

 underlying Oligo- 

 cene strata (Chad- 

 ron beds and Brule 

 formation), of much 

 less thickness than 

 the equivalent 

 White River beds 

 of the South Da- 

 kota section. 



Lower John Day beds, 

 transitional between 

 Oligocene and Mio- 

 cene, of continuous de- 

 position with the Mid- 

 dle John Day beds^ 

 and resting unconform- 

 ably upon the Clarno 

 beds of undoubted 

 Eocene age. 



South Dakota, also, the Lower Miocene falls naturally into a 

 two-fold instead of a tripartite division as in Nebraska, the two 

 members of the series being known as the Lower and Upper 

 Rosebud beds. The Lower John Day beds of Oregon are of 

 transitional character, and may be classed as either uppermost 

 Oligocene or lowermost Miocene, the difficulty being that 

 they are not separated from the Middle John Day beds by any 

 apparent stratigraphic break. 



An earlier and somewhat different correlation of the section 

 in the John Day Basin than that which is here proposed by 

 Mr. Peterson will be found in an article by Drs. J. C. Merriam 

 and W. J. Sinclair on the Tertiary Faunas of the John Dav 

 Region (Bull. Dept. Geol. Univ. Cal., 1907, vol. v, No. 11). 

 For the benefit of those interested in the correlation of Euro- 

 pean formations reference may be made to the following recent 

 papers : 



Dollfus, G. F. ; Essai sur l'Etage Aquitanien. Bull. Serv. Carte Geol. 

 France, 1910. vol. xix, no. 124. [The Aquitanian is here considered as 

 Lower Miocene.] 



Stehlin, H. G. ; Bemarques sur les faunules de mammiferes des couches 

 eocenes et oligocenes du Bassin du Paris. Bull. Soc. Geol. France, 1912, (4) 

 vol. ix. See also his Revision of European Anthracotheres, 1910. 



Glangeaud, P. ; Les facies de l'Oligocene aux environs de Bergerac et 

 dans le Dordogne, 1912, loc. cit. 



Haug, E. ; La Periode Neogene, in his ' Traite de Geologie,' 1911, vol. ii, 

 fasc. 3. 



Perisho, E. C, and Visher, S. S. ; South Dakota Geol. Surv., 1912, Bull. 

 No. 5. 



