Vol. 5] 



Merriam^Sinclair. — Tertiary Faunas. 



193 



Protapirus is also unrepresented in the Middle John Day. The 

 introduction of these two genera may be explained by their 

 immigration from some other province, as they are without 

 known ancestral forms in the Middle John Day. Agriochoerus 

 decreases in abundance in the Upper John Day, where it is 

 represented by bizarre forms like A. ferox. Large elotheres are 

 more common than in the Diceratherium beds. The smaller hogs 

 have not been found in the upper division. Rodents are not 

 well represented. Camels have been found only in the upper- 

 most beds of the series. Plains and forest types occur together 

 in the same beds. 



Age. — Stratigraphically, the John Day occupies a position 

 between the Upper Clarno (Upper Eocene) and the Columbia 

 Lava. Prom the latter it is separated by an interval of de- 

 formation, and sub-aerial erosion. Before considering the age 

 of the John Day it will be advisable to present briefly what is 

 known regarding the age of the lava. 



The Columbia Lava is evidently referable to the earlier 

 Miocene, as it is overlain by the Mascall of the later Miocene. 

 Its correlative is the Yakima basalt of the Ellensberg quadrangle, 

 which bears the same relation to the Ellensberg formation that 

 the Columbia Lava does to the Mascall, the equivalent of the 

 Ellensberg. By Smith 40 the age of the Yakima basalt is fixed 

 as early or middle Miocene from the fact that the basalt rests 

 unconformably on the Manastash formation (Upper Eocene= 

 Clarno) without the intervention of the John Day. 



The time equivalent of the unconformity at the top of the 

 John Day can not be accurately measured. At a number of 

 localities the upper beds are wanting, the lava resting on the 

 Middle John Day. Elsewhere, the erosion is represented by 

 gulches carved into the John Day tuffs and preserved beneath 

 the lava cap. Taken in connection with the great thickness of 

 the lava it seems reasonable to regard the volcanic and erosion 

 intervals together as equivalent to a considerable part of the 

 earlier Miocene. 



A strict adherence to the three-fold subdivision of the Ter- 

 tiary would necessitate placing the John Day in the Lower 



4J G. O. Smith. Professional Paper U. S. G. S., No. 19, p. 16. 



