Vol. 5] 



Merriam. — John Day Carniuora. 



3 



OCCURRENCE. 



The general stratigraphic succession of the Tertiary forma- 

 tions of the John Day region has been discussed by the writer in 

 a previous paper.'-' The sequence of formations recognized is as 

 follows : — 



John Day River terraces Quaternary 

 Kattlesnake formation Pliocene 

 Mascall formation Miocene 

 Columbia Lava formation Miocene 

 John Day series Miocene to Oligocene 



Upper John Day 

 Middle John Day 

 Lower John Day 

 Clarno formation Eocene 

 Upper Clarno 

 Lower Clarno 



Of these formations, those included in the beds below the 

 Pliocene are made up mainly of igneous materials. The John 

 Day and Mascall beds are almost entirely composed of volcanic 

 ash and tuff in various forms. Mammal remains are known from 

 the John Day, Mascall, Battlesnake, and Terrace deposits. 



Excepting the uppermost portion of the series, the John Day 

 beds show a remarkable evenness in their stratification, and con- 

 tain a fauna which is characteristic of dry land. In the higher 

 strata, cross-bedding appears, with more or less interstratified 

 gravel, and a number of fresh-water types are seen in the fauna. 

 The greater portion of the series is presumably made up of slow 

 accumtilations of ash, which fell mainly on open plains, upon 

 which shifting shallow lakes may have existed from time to time. 

 In the latter portion of this period the topography appears to 

 have been more diversified and the action of streams to have be- 

 come more pronounced. 



The greater portion of the total thickness of the Mascall is, 

 like the John Day, made up of evenly stratified ash beds. In the 

 Lower portion of the formation there is, however, evidence of ac- 

 cumulation of a considerable thickness of fine sediment in a body 

 of fresh water, [n 1his there are numerous remains of fresh- 

 water fishes and mollusks, and large quantities of fossil plants. 



The Rattlesnake beds consist mainly of heavy gravels. Asso- 



- Bull. Dept. Geol., Univ. Cal., Vol. 2, No. 9. 



