

1918] Fan Winkle: Paleontology of the Oligocene 71 



the Oligocene. Mr. Hannibal states, "The shales overlying the basal Astoria basalts 

 north and east of Oakville, Porter and Elma; and the lowest Oligocene exposed at 

 Lincoln Creek belong to the San Lorenzo formation." Several faunal localities in 

 the vicinity of Porter Creek are listed as well as the fauna occurring at these places. 

 He considers the San Lorenzo formation in the Grays Harbor area to have a 

 thickness of 3,000 feet. 



In a report published in 1916 by Dr. C. E. Weaver 7 on the "Tertiary Faunal 

 Horizons of Western Washington" the Oligocene strata occurring in the Porter 

 Creek area are referred to as the Porter Horizon, which is considered to be of 

 middle Oligocene age. A list is given of the fauna occurring in this horizon and 

 also those species which are most characteristic of it. This fauna is referred to as 

 the Turritella porterensis Zone. The fauna is regarded as being distinct from the 

 lower beds exposed at Lincoln Creek and also from the upper beds at Restoration 

 Point. Evidence for subdividing the Oligocene into three distinct formations did 

 not seem warranted; however, three faunal zones were recognized, and the middle 

 one of these was referred to as the Porter Horizon. Several new species were 

 described from this area. 



Later in the same year a detailed paper appeared by Dr. Weaver 8 dealing with 

 the stratigraphy of the Tertiary of western Washington. This report is accom- 

 panied by areal geologic maps and cross sections. Upon these maps the distribution 

 of the Oligocene sediments in the vicinity of Porter Creek is shown as well as the 

 structural details. A list of the faunal species occurring here is also given. The 

 strata are referred to as the Porter Horizon and the fauna contained within these 

 strata are grouped as the Turritella porterensis Zone. 



During the summer of 1917 a paper appeared by Dr. Roy E. Dickerson,, 9 in 

 which he describes a marine invertebrate fauna of 48 species which was collected 

 by Mr. F. M. Anderson and Mr. Bruce Martin. Thirty-six of these species are 

 new. This fauna occurs in a sandstone formation associated with conglomerate 

 which outcrops at the Greece ranch on the east bank of Cowlitz River, about four 

 miles east of Vader, Washington. Dr. Dickerson believes this fauna to be of 

 Oligocene age and to represent a lower phase of the Molopophorous lincolnensis 

 Zone as exposed on Lincoln Creek. 



STRATIGRAPHY 



The Oligocene formations in southwestern Washington occupy three areas 

 which appear to have been laid down originally in a long narrow marine embayment 

 extending from Grays Harbor along the Chehalis Valley southeasterly to a point 

 four miles east of Vader on the Cowlitz River. The westernmost of these areas 

 lies between Oakville and Porter. The middle area lies between Helsing Junction 



7 Weaver, C. E. The Tertiary Faunal Horizons of Western Washington, Univ. Wash. 

 Publ. in Geol., vol. 1, No. 1, pp. 1-66, 1916. 



8 Weaver, C. E. The Tertiary Formations of Western Washington, Wash. Geol. Survey 

 Bull. No. 13, pp. 180. 206 and 207, 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. 157-192, 1917. 



