1916] Weaver: Tertiary Faunal Horizons 7 



rad, Venericardia quadrata Dall, Chione olympidea Reagan, Chione clallamensis 

 Reagan, Ficus clallamensis Weaver, Crepidula praerupta Conrad, Fusinus stan- 

 fordensis (Arnold), Polynices saxea (Conrad), Sinum scopulosum Conrad, Denta- 

 lium conradi Dall and Aturia angustata Conrad. 



UPPER MIOCENE 



There is ample evidence in Washington that there occurred during the middle 

 Miocene the most marked crustal movements since the close of the Jurassic. The 

 upper Miocene strata are everywhere unconformable upon the older rocks. The 

 great unconformity of the middle Miocene is not confined to the state of Wash- 

 ington alone, but is just as well defined in Oregon and California. Near the 

 close of the lower Miocene epoch the larger part of western Washington appears 

 to have been elevated above sea level and the older Tertiary sediments more or 

 less folded. Early in the upper Miocene two new embayments were developed. 

 One of these occupied a part of the Grays Harbor region and the other covered a 

 small area near the mouth of the Quillayute River in southwestern Clallam County. 

 In the former area at least 5,000 feet of sediments accumulated and in the latter 

 about 1,000 feet. These deposits consist for the most part of coarse grained 

 brownish sandstones and conglomerates together with minor amounts of shales and 

 sandy shales. 



These sediments may be the equivalent of the Empire Formation of Oregon 

 and the San Pablo of California. It is impossible with present evidence to de- 

 termine whether they represent more or less. These deposits have formerly been 

 referred to by the writer as the Montesano formation but if at some later time 

 there is direct proof that they are the equivalent of the Empire formation, the 

 present name can be dropped and the term Empire be adopted for the upper Mio- 

 cene of both Oregon and Washington. There is very little variation in the char- 

 acter of the contained faunas from the base to the top of the formation. The 

 faunas, however, occurring at the mouth of Queniult River may represent a slightly 

 higher zone. The term Yoldia strigata Zone is applied to the faunas occurring 

 within this formation from the persistent occurrence of this most common species. 



The following species are most characteristic of this zone: Area trilineata 

 Conrad, Cardium meekianum Gabb, Macoma astori Dall, Mulinea alia Weaver, 

 Mulinea undulifera Weaver, Pecten coosensis Schumard, Solen sicarius Gould, 

 Yoldia strigata Dall, Argobuccinum cammani Dall, Chrysodomus imperiallis Dall, 

 Phalium aequisulcatum Dall, Sinum scopulosum and Scutella gabbii Remond. All 

 of the species occurring within this zone are entirely marine types. 



All of western Washington with the possible exception of the Strait of Juan 

 de Fuca appears to have been a land area. No marine deposits are known to occur 

 within the state younger in age than those at the mouth of Queniult River with the 

 exception of late Pleistocene beach sands about the shores of Puget Sound. The 

 history of the Pliocene in western Washington must be sought in terms of diastro- 

 phism and erosion. 



