78 University of Washington Publications in Geology [Vol. 1 



The Acila gettysburgensis fauna lived in waters ranging from shallow to 

 moderate depth and under climatic conditions which were much more temperate 

 than those in existence during the lower and middle Oligocene. 



CORRELATION 



In a preliminary report by Dr. C. E. Weaver 1 in 1912, the Oligocene and 

 lower Miocene formations in western Washington were described and provisionally 

 divided into four formations. In the following year Arnold and Hannibal 2 divided 

 the Oligocene of Washington into three divisions, which they termed the San 

 Lorenzo, the Seattle, and the Twin River. They grouped them as the Astoria series. 



Later more detailed field studies were made by Dr. Weaver" on the Oligocene 

 formations in western Washington, and he divided the faunas of the Oligocene as a 

 whole into three faunal zones, which he termed the Molopophorous lincolnensis 

 Zone, the Turritella porterensis Zone and the Acila gettysburgensis Zone. The sedi- 

 ments containing these faunas he referred to as the Lincoln, Porter and Blakeley 

 horizons. The Lincoln was regarded as the oldest or basal portion of the Oligocene. 



Studies made by Dr. Dickerson 4 in the Greece ranch locality show that the 

 fauna represented there is probably to be correlated with the lower portion of the 

 Molopophorous lincolnensis Zone. 



The fauna contained in the lower Porter beds as exposed at Oakville and 

 on Porter Creek consist of thirteen species, all of which are typical shallow water 

 or shore forms. This fauna resembles that of the Sooke beds on Vancouver Island, 

 but sufficient evidence is not available for direct correlation. The lower Porter 

 fauna is tropical to subtropical, as evidenced by the presence of Cypraea. This 

 may be hereafter referred to as the Barbatia merriami Zone. The upper Porter 

 fauna, which has been designated as the Turritella porterensis Zone, consists of 

 thirty-five species. This fauna is a typical moderate to deep water group, and 

 thus accounts for the small number of species in common with the lower Porter zone. 



The fauna found in the Lincoln Creek beds, which are referred to as the 

 Molopophorous lincolnensis Zone, consists of fifty-nine species. These are moderat 

 to deep water types and subtropical in character.- Twenty-six species of the Molo- 

 pophorous lincolnensis fauna are found in the upper Porter beds. 



The Acila gettysburgensis Zone as exposed in the Puget Sound Oligocene 

 embayment, consists of forty-nine species, eighteen of which are common to the 

 Molopophorous Zone and fifteen common to the Porter beds. The fauna contained 

 in the uppermost part of the Porter beds consists of such species as Thyasira bisecta 

 Conrad, Thracia trapezoidea Conrad, Phacoides acutilineatus Conrad, which do not 



1 Weaver, C. E. A Preliminary Report on the Tertiary Paleontology of Western Wash- 

 ington. Bull. 15, Wash. Geol. Surv., pp. 15-17, 1912. 



2 Arnold, R., and Hannibal, H. The Marine Tertiary Stratigraphy of the North Pacific 

 Coast of America, Proc. Amer. Phil. Soc.. vol. 52. p. 582. 1913. 



T> H* We Ve i r> C - E> , Tertiai< y Faunal Horizons of Western Washington, Univ. of Wash. 

 Pub. in Geology, vol. 1, No. 1, pp. 4-6, 1916. 



* Dickerson, Roy E. Climate and Its Influence on the Oligocene Faunas of the Pacific 

 Coast, with Descriptions of some new Species from the Molopophorous lincolnensis Zone, 

 Proc. Cal. Acad. Sci., Fourth Series, vol. 7, pp. 157-159, 1917. 



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