456 / HARLEN BRETZ 



be complete. However, the position of the mantle of loose pebbles 

 is so strikingly similar to that of the stratified Satsop on the southern 

 flank of the Simcoe Range and throughout the Cascade Range that 

 ittle hesitation is felt in correlating the eroded surface named the 

 "Methow peneplain" with the eroded surface beneath the Satsop 

 formation in the Cascade Range. 



But this eroded surface as exposed in the Columbia Gorge is 

 irregular and numerous elevations in it rise several hundred feet 

 above the base of the Satsop. This is well shown in the Willamette 

 valley and the Hood River valley where these hills of basalt rise 

 through the Satsop formation and the younger lavas. The surface 

 on which the Satsop rests in the sections of the Columbia Gorge 

 may be post-maturely eroded, but it is not a peneplain. 



Further, it has been shown in this paper that the Coast Range 

 rises above the Satsop formation in the Chehalis, Willapa, Willa- 

 mette, and lower Columbia valleys and therefore was not a pene- 

 plain at the time of Satsop deposition. 



The age of the Satsop formation. — Diller 1 reports that W. H. 

 Dall found all of the species in a collection of shells from the 

 Quaternary deposits on Yaquina Bay, Oregon, to be living forms. 

 He also states that F. A. Lucas identified a large tooth from the 

 same beds as that of a Pleistocene mastodon and that F. H. Knowl- 

 ton identified cones from this formation as those of " Picea stichensis 

 Carr.," the tideland spruce growing along this coast today. 



In another paper 2 Diller has described deposits between Cape 

 Blanco and Elk River, Oregon, about 50 miles north of the Cali- 

 fornia line, which he names "Elk River beds." Dall states that 

 the fossils collected from these beds are probably Pleistocene in age. 

 Martin 3 has more recently examined the Cape Blanco region and 

 reports two faunal horizons in the Elk River beds, the upper of 

 which is very closely related to the Upper San Pedro series and "is 



1 J. S. Diller, "A Geological Reconnaissance in Northwestern Oregon," U. S. Geol. 

 Surv., 17th Ann. Rept., Part I, 1896. 



2 J. S. Diller, "The Topographic Development of the Klamath Mountains," 

 U.S. Geol. Surv., Bull. ig6, 1902, p. 30. 



3 Bruce Martin, "The Pliocene of Middle and Northern California," Univ. of Cal. 

 Publications, Bull. Dept. Geol., IX, No. 15 (19 16). 



