THE SATSOP FORMATION 457 



at least Pleistocene in age" and the lower of which probably is very 

 late Pliocene. The Elk River beds overlie the Empire beds with 

 angular unconformity. Ralph Arnold and B. L. Clark 1 consider 

 that the fauna of the Empire beds is "of very nearly the same age 

 as that of the Purisima formation in the Santa Cruz Mountains 

 of California, which is Pliocene, and not the oldest Pliocene" 

 (Clark). The Elk River beds are apparently the same as the 

 deposits of the Oregon coast farther north, which Diller called 

 Quaternary. 



Ralph Arnold, 2 in a description of the geology of the coast of 

 the Olympic Peninsula of Washington, maps and names what is 

 here called the Satsop formation as "Pleistocene gravel, sand, and 

 clay." He notes the presence of tilted Pliocene beds (his Quinault 

 formation), bearing a fauna similar to that of the Purisima forma- 

 tion of California. On these beds the Satsop formation rests with 

 angular unconformity. B. L. Clark 3 believes that present knowl- 

 edge of the Pliocene faunas of the Pacific Coast upholds Arnold's 

 determination and that the scarcity of extinct species suggests 

 strongly that the fauna is rather late Pliocene in age, though not 

 the latest Pliocene. 



Harold Hannibal, 4 in a paper by Ralph Arnold and himself, 

 notes the Quaternary age of the oyster-shell bed in the Satsop 

 formation of the Willapa Bay region. 



Diller also collected fossil shells from shales 700 A.T. on the 

 slopes of the Columbia valley 35 miles from the coast. Dall refers 

 the shells to the Pliocene. The Satsop here is a terrace gravel down 

 in the valley and younger than the Pliocene beds. 



A clay stratum with abundant fossil leaves has been found in the 

 Satsop formation on the western slope of the Cascade Range. 

 Knowlton has examined collections from this bed and is of the 

 opinion that the flora is Quaternary in age. He finds leaves of 



1 Personal communication. 



2 Ralph Arnold, "A Geological Reconnaissance of the Coast of the Olympic Penin- 

 sula, Washington," Bull. Geol. Soc. Am., XVII (1906), 451. 



3 Personal communication. 



4 Arnold and Hannibal, "The Marine Tertiary Stratigraphy of the North Pacific 

 Coast of America," Proc. Am. Philos. Soc, 1913. 



