Clark: The San Lorenzo Series of Middle California 103 



Summary of Oligocene Sequence in Oregon, Washington and Vancouver 

 Island as Kecognized by Different Writers up to the Present Time 



Weaver, 1912 

 Wahkiakum, re- 

 ferred to the 

 Miocene 



Arnold and 

 Hannibal. 1913 

 Monterey 



As recognized by 

 Weaver, 1916 writer, 1917 



Wahkiakum Monterey group 



Area monterey- Area monterey- 



Blakeley forma- Astoria series 

 tion, referred to Twin Eiver 

 the Lower Miocene formation 



. Seattle forma- 

 tion 



Lincoln formation, San Lorenzo 

 referred to the formation 

 Oligocene 



Sooke forma- 

 tion 



ana zone 



Clallam forma- 

 tion 

 Blakeley hori- 

 zon — Aeila 

 gettysburg- 

 ensis zone 

 Porter horizon 

 Turritella por- 

 terensis zone 

 Lincoln horizon 

 Molopophorus 

 lincolnensis 

 zone 



ana zone 



San Lorenzo series 

 Acila gettys- 

 burgensis zone 



Molopophorus 

 lincolnensis 



Fauna of 

 Sooke beds 



Thus, as shown above in the column to the right, three distinct 

 faunas are now recognized in Oregon, Washington and British Colum- 

 bia as belonging between the Tejon (Upper Eocene) and the Monterey 

 (Lower Miocene) and these faunas are considered to be of Oligocene 

 age, the beds in which they are found being referred to the San 

 Lorenzo series. The lower fauna, that of the Sooke beds, is very 

 distinct from that of the Molopophorus lincolnensis zone, the beds of 

 the latter in a number of localities lie immediately above those con- 

 taining the Sooke fauna. The upper fauna, that of the Acila gettys- 

 burgensis zone, is likewise distinct from that of the Molopophorus 

 lincolnensis zone. 



Of the one hundred and thirteen determinable species known 

 from the San Lorenzo beds of Mount Diablo, more than forty have 

 been recognized by the writer in the Oligocene collections from Oregon, 

 Washington and British Columbia; of these species, only eight are 

 known for a certainty to extend into the lower Miocene. This makes 

 a total of over thirty species common between the known Oligocene 

 fauna from the northern localities and the fauna from the San 

 Lorenzo beds of Mount Diablo, none of which species have as yet 

 been found in beds higher than those usually assigned to the Oligocene. 



