102 



University of California Publications in Geology [Vol. ll 



Of the thirteen species listed above, eleven are found in the Oligo- 

 cene of Oregon and Washington ; two of these, Agasoma gravidum 

 and Fusinus (Exilia) lincolnensis, are known for a certainty in only 

 the lower phase of the Oligocene of Oregon and Washington, as 

 recognized by Arnold and Hannibal and by Weaver. 



KELATTON TO OLIGOCENE OF OEEGON, WASHINGTON AND 

 BRITISH COLUMBIA 



Reference has already been made to the work of Arnold and Han- 

 nibal 73 on the Oligocene of Oregon, Washington and Vancouver Island 

 and to that of Weaver on the Oligocene of Washington. The former 

 writers, it will be remembered, recognized four horizons between the 

 Upper Eocene (Tejon) and the Monterey (Lower Miocene) ; these 

 were designated, beginning with the oldest, the Sooke formation, the 

 San Lorenzo formation, the Seattle formation and the Twin River 

 formation. Weaver, 74 in his more recent publications, separates the 

 fauna of the marine Oligocene beds of Washington, which he refers 

 to the Clallam formation, into three faunal zones, the lowest of which 

 he names the Molopophorus lincolnensis zone and refers to as the 

 Lincoln horizon; the middle zone is called the Turritella porterensis 

 zone or Porter horizon ; the upper, the Acila gettysburgensis zone, is 

 referred to as the Blakely horizon. 



Weaver now recognizes that his Molopophorus lincolnensis and 

 Turritella porterensis zones are very closely related, if not exactly 

 equivalent, and it is agreed hereafter to refer to them as belonging 

 to one zone, the name Molopophorus lincolnensis zone being used to 

 designate that horizon. Thus, the Molopophorus lincolnensis zone, as 

 redefined, is equivalent to the fauna of the San Lorenzo formation 

 of Arnold and Hannibal. Weaver's study of the section around 

 Puget Sound apparently shows that the Twin River formation of 

 Arnold and Hannibal is the equivalent of their Seattle ; the fauna 

 from these beds is the equivalent of that of Weaver's Acila gettys- 

 burgensis zone. 



73 Arnold, Ralph, and Hannibal, Harold, The marine Tertiary stratigraphy of 

 the North Pacific Coast of America, Proc. Amer. Philos. Soc, vol. 52, pp. 573-589, 

 1912. 



Weaver, C. E., Tertiary faunal horizons of western Washington, Univ. Wash. 

 Publ. Geol., vol. 1, no. 1, pp. 1-67, 1916. Post-Eocene formations of western 

 Washington, Proc. Calif. Acad. Sci., ser. 4, vol. 6, no. 2, pp. 19-40, 1916. Tertiary 

 formations of western Washington, Wash. State Surv., Bull. 13, pp. 1-327, 1916. 



