SALIENT FEATURES OF THE GEOLOGY OF OREGON 95 



has yet to be reported. It is, however, presumed that a hiatus 

 between the two will be found. 



These terrestrial beds have yielded fossil plants only, which 

 were early discovered at Bridge Creek by Condon. The flora, as 

 determined by Knowlton, comprises about twenty-five forms, which 

 indicate the Eocene age of the formation. There is some evidence 

 that both the lower and upper Eocene floras are represented. 



In Malheur and Harney counties a series of sedimentary beds 

 occupies, in part, the Snake River Valley from a point near Owyhee 

 northward to Ontario, extending westward to a locality some thirty 

 miles southwest of Vale. 



These beds consist mainly of unconsolidated gravels, sands, clays, 

 and volcanic ash. Similar beds along Snake River in Idaho have 

 been described by Lindgren^ as the Payette formation. He ascribes 

 their origin to a large Neocene lake, but RusselP inclined to the belief 

 that the Oregon beds were of fluvatile origin. These may well in- 

 clude other Tertiary strata, as Washburne^ suggests, and as is appar- 

 ently proved by Merriam^ by the discovery of the Ironside formation 

 at Ironside. The fossil leaves and fresh-water mollusks indicate 

 an early Tertiary age for these beds. The Payette has been corre- 

 lated with the lone. Upper Eocene of California, upon the basis of 

 fossil plants, and with the Upper Clarno of the John Day Valley 

 by Merriam. If it is the equivalent of the Upper Clarno the sedi- 

 mentation was much more rapid in the Payette Basin. 



OUgocene. — Certain marine beds at Astoria, well known through 

 the early work of Dana, Conrad, and Condon, were the first of the 

 entire coast to be assigned to the Oligocene. The basis upon which 

 the correlation was first made by Dall has not as yet been discussed. 

 This Astoria section now serves as the type section for the west- 

 coast Oligocene, which is now known to be well developed in the 

 adjoining states. 



In Oregon, Oligocene faunas have been identified by Clark^ and 

 others from a number of localities, mainly in Clatsop, Columbia, 



' W. Lindgren, U.S. Geol. Surv., Folio 103, p. 2. 



^ I. C. Russell, ibid., Bull. 252, p. 31. 



■' C. Washburne, ibid., Bull. 431, p. 27. 



'' J. C. Merriam, op. ciL, X, in. 



s B. L. Clark, Univ. Col. Publ., Bull. Dept. Geol., II, 102. 



