4 University of Washington Publications in Geology [Vol. 1 



certainly older than those one and one half miles east of Vader as determined 

 by detailed stratigraphic measurements. 



A list of all known species occurring in the Eocene of western Washington 

 as well as the localities at which they occur may be referred to in the accompanying 

 tables. 



OLIGOCENE 



Deposits formed during the Oligocene epoch are for the most part of marine 

 origin. They attain a maximum aggregate thickness of nearly 15,000 feet in the 

 Cape Flattery section. In the Puget Sound Basin and in southwestern Washington 

 they range in thickness from 1,000 to 10,000 feet. Marine fossils are abundant 

 within the Oligocene deposits and constitute several faunal zones. 



There does not seem to be sufficient evidence to divide the strata of the Oli- 

 gocene into a series of formations. Possibly future studies may make such a 

 procedure desirable. At the present time three distinct faunal zones can be rec- 

 ognized and the deposits in which these faunas occur are referred to as the Clallam 

 formation. The faunal zones beginning with the oldest are the Molopophorous 

 lincolnensis Zone, the Turritella porterensis Zone and the Acila gettysburgensis 

 Zone. The corresponding sedimentary deposits containing these zones may be 

 referred to as the Lincoln, Porter and Blakeley horizons. The term horizon is 

 used in the sense of a deposit formed at a particular time and identified by dis- 

 tinctive fossils. The faunas occurring in each of the following zones are distinct 

 and many of the species do not range into the zones below or above. 



Molopophorous lincolnensis Zone The type section in which this fauna 

 occurs is situated in Thurston County along the banks of the Chehalis River be- 

 tween five and ten miles west of the city of Centralia and west of the mouth of 

 Lincoln Creek. Strata of equivalent age occur on Porter Creek to the west, 

 stratigraphically below the Porter Horizon or Turritella porterensis Zone. Litho- 

 logically the deposits are composed of somewhat massive sandy shales and shaly 

 sandstones moderatly consolidated. 



The most characteristic species of this zone are: Acila schumardi, Cardium 

 lorenzanum (Arnold), Cras satellites washingtonensis Weaver, Glycymeris cheha- 

 lisensis n. sp., Leda washingtonensis n. sp., Pitaria dalli n. sp., Macrocallista pitts- 

 burgensis Dall, Dentalium substramineum Conrad, Calyptraea excentrica (Gabb), 

 Exilia dickersoni Weaver, Exilia lincolnensis n. sp., Hemifusus washingtonensis 

 Weaver, Drillia hecoxi (Arnold), Natica lincolnensis n. sp., Molopophorous lincoln- 

 ensis n. sp., Strepsidura washingtonensis n. sp., and Turris thurstonensis n. sp. 



Several species occurring in this faunal Zone also occur in the typical Tejon 

 fauna near Vader. The following species have been noted in common: Crassatel- 

 lites washingtonensis Weaver, Leda gabbi Conrad, Solen parallelus Gabb, Den- 

 talium substramineum Gabb, Calyptraea excentrica (Gabb), Exilia dickersoni 

 Weaver, Hemifusus washingtonensis Weaver, and Strepsidura washingtonensis 

 n. sp. 



