22 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



The most recent paper on the Tertiary of western Wash- 

 ington is by Arnold and HannibaP on the Marine Stratigraphy 

 of the North Pacific Coast of America, pubHshed in 1913. A 

 four-fold division of the Oligocene is recognized. The oldest 

 is represented by the Sooke formation of southwestern Van- 

 couver Island. This is followed by the San Lorenzo, Seattle 

 and Twin River formations. Above this is the Monterey, 

 which is thought to be in part Oligocene and possibly in part 

 lower Miocene. The upper Miocene strata, which are de- 

 scribed as occurring on the south and west portions of the 

 Olympic Peninsula, are believed to be the equivalent of the 

 Empire foniiation of Coos Bay, Oregon. 



GEOGRAPHIC DISTRIBUTION 



The Oligocene and Miocene deposits of western Wash- 

 ington exist in three separate areas. The largest and most 

 representative area occupies the northern half of the Puget 

 Sound basin and the north border of the Olympic Peninsula. 

 A second area embraces the western portion of the Chehalis 

 and Willapa river valleys in the southwestern part of the 

 state. A third area constitutes a belt ranging from five to 

 fifteen miles in width and trending east and west along the 

 north shore of Columbia River. Within the Puget Sound 

 basin and along the northern portion of the Olympic Penin- 

 sula, Miocene sediments are for the most part more or less 

 heavily covered with deposits of glacial drift. They appear 

 in the form of low sea cliffs along the shores of the entrance 

 to the Bremerton Navy Yard, in the streets in the southern 

 portions of the city of Seattle, and along the northern slopes 

 of the Newcastle Hills. Along the north border of the Olym- 

 pic Peninsula rock exposures appear almost continuously from 

 Cape Flattery eastward to Port Crescent. Similar deposits 

 occur within and along the shores of portions of the Ouimper 

 Peninsula south of Port Townsend. The Puget Sound Basin 

 Oligocene and Miocene area is separated from that of south- 

 western Washington by basalts and sedimentary rocks of Eo- 

 cene age. From the southern margin of the Olympic Moun- 



^Arnold, Ralph, and Hannibal, Harold, "Marine Stratigraphy of the North Pacific 

 Coast of America," Proc. Amer. /Philos. Soc, vol. 53, No. 212, November-December, 

 1913. 



