THE EOCENE OF NORTH AMERICA 4^3' 



" formation is composed of an extensive series of conglom- 

 erates, sandstones and shales, with terraces here and there of 

 calcareous siliceous beds, which, although of small extent, on- 

 account of their exceptional character are treated separately as 

 the Wilbur formation." * The Umpqua formation has a maxi- 

 mum exposure of about twelve thousand feet The beds thicken 

 toward the northwest. The bowlders of the Umpqua formation 

 become larger toward the east and south, showing that the land 

 from which they were derived lay in this direction. In places 

 the Umpqua contains abundant marine fossils, Cardita planicosta 

 and Turritella uvasaria being typical Eocene forms. Thin, small 

 beds of coal also occur. 



THE TYEE SANDSTONE 



The Tyee sandstone occupies a small area in the vicinity of 

 Roseburg, Ore. "It immediately overlies the Umpqua forma- 

 tion, from whose sandstones it differs chiefly in being heavier 

 bedded and containing more conspicuous scales of mica." 2 It 

 reaches a thickness of about iooo feet. In places it contains 

 characteristic marine Eocene fossils. The position of the 

 Umpqua and Tyee beds in the geological column cannot be 

 given with certainty. They overlie the Myrtle beds which,, 

 according to Stanton, belong to "the lower half of the Upper 

 Cretaceous." 3 Upon the Umpqua, in apparent conformity, lies 

 the "Oakland limestone-lentils" of "probably Oligocene, most 

 likely Upper Oligocene" age. 4 From these relations, from their 

 geographical position and from their fossils I place the Umpqua 

 and Tyee provisionally in the column above the Tejon. If this 

 be their true position they form the latest marine Eocene beds, 

 known on the Pacific coast. 



THE ATURIA FORMATION 



The Aturia beds occur at the water's edge at Astoria, Ore.. 

 Formerly they were not distinguished from the overlying shales 

 and sandstones. But in 1880 Condon 5 showed that they are 



1 Diller: loc. cit. 2 Ibid. 3 Quoted by Diller, loc. cit. 



4 Diller: loc. cit. SAmer. Naturalist, Vol. XIV, 1880. 



