SALIENT FEATURES OF THE GEOLOGY OF OREGON 97 



sist of marine sandstones and shales of as yet an undetermined 

 thickness. 



An invertebrate Monterey fauna is reported by Arnold and 

 HannibaP from Astoria, Mountain Dale, Westpoint, Tillimook, 

 and along the ocean shore in the vicinity of Newport. Much, if not 

 all, of the reported Miocene in the Coast Ranges and the Willamette 

 Valley is now assigned to the Oligocene. A fauna of over thirty 

 species has been obtained by Hannibal at Astoria, including Area 

 devincta Conrad, Pecten propatulus Conrad, Turritella oregonensis 

 Conrad. These are thought by him to be characteristic of the 

 Monterey of California, which is of lower Miocene age. Marine 

 vertebrates, including Desmostylus hesperus Marsh, and Desmato- 

 phoca oregonensis Condon, have been found in these beds in the 

 vicinity of Newport. These important fossils point to a middle 

 Tertiary age of these beds. 



The upper Neocene beds were described by Diller^ as the Empire 

 and assigned to the Miocene. They are known from the Coos Bay 

 and Port Orford quadrangles, where they consist of light-colored 

 shales and sandstones, which are in places massive. These rocks, 

 aggregating about five hundred feet in thickness, lie unconformably 

 upon the folded edges of the Eocene sediments, and in turn are 

 disconformable with the overlying Pleistocene deposits. 



Ball's^ list of 90 species of marine vertebrates from the Empire 

 has been considerably extended by subsequent workers. This 

 formation until recently considered of Miocene age is now thought 

 to belong to the early Pliocene.'' 



Unconformably overlying the Empire beds at Fossil Point, 

 Coos Bay, is a mass of heavy conglomerates known as the Coos 

 conglomerates, some thirty feet in thickness, which has yielded a 

 small marine fauna, considered Pleistocene by Dall,^ but Pliocene 

 by several other workers. 



Terrestrial beds discovered by LeConte and more recently 

 described by Williams^ as the Eagle Creek formation occur at or near 



' R. Arnold and H. Hannibal, Proc. Am. Phil. Soc, LII, 576. 

 ^ J. Diller, U.S. Geol. Siirv., 17th Ann. Kept., Part I, p. 475. 



3 W. H. DaU, U.S. Geol. Surv., Prof. Paper 59, p. 18. 



4 B. L. Clark, and R. Arnold, Bull. Geol. Soc. Am., XXIX, 298. 



5 W. H. DaU, op. cit., p. 19. 



^ I. A. Williams, Mineral Resources of Oregon, Oregon State Min. Bur., II, 80. 



