Vol. VI] WEAVER— OLIGOCENE OF KITSAP CO., WASH. 45 



shore of the Strait of Juan de Fuca between Pysht and Clallam 

 Bay. The strata are referred to as the Wahkiakum horizon. 

 Resting unconformably upon the Oligocene and lower Mio- 

 cene sediments are shallow water deposits of upper Miocene 

 age containing a distinctive fauna which may be referred to 

 as the Yoldia strigata zone, or Montesano horizon. 



STRATIGRAPHY 



From the western spur of the Cascade Mountains in King 

 County, a prominent spur extends nearly due west into the 

 Puget Sound basin. This spur includes the Issaquah and 

 Newcastle hills. From Lake Washington it trends westerly 

 through Seattle as a pre-glacial and, in part, submarine topo- 

 graphic feature. It crosses the Sound a little to the south of 

 Bainbridge Island and reappears in the Bald Hills of central 

 Kitsap County. Structurally this ridge is of anticlinal origin. 

 Sedimentary and volcanic rocks of Eocene and Oligocene age 

 are involved within it. Extensive erosion has deeply cut into 

 it so that the Oligocene strata have been completely removed^ 

 from the axis. The core is largely composed of Eocene basalts 

 together with brackish water and marine sediments. The coal 

 measures at Issaquah and Newcastle, together with the sand- 

 stone and shales between Duwamish and Renton, belong to 

 this phase. The basalts which outcrop on the shores of Sinclair 

 Inlet, as well as those southwest of Bremerton in the Bald 

 Hills, belong to the basaltic phase of the Tejon-Eocene. Rest- 

 ing unconformably upon the Eocene rocks and forming a part 

 of the north flank of the anticline just mentioned, are sand- 

 stone and shales of Oligocene age. These strata are exposed 

 in the north slopes of the Newcastle Hills, in the street cuts 

 of Columbia City and Georgetown (both of which are within 

 the city limits of Seattle), along the shores of Bailey Peninsula 

 and at Alki Point. West from Seattle they outcrop at the 

 water's edge at the south end of Bainbridge Island and along 

 the south shores of Richs Passage. They appear for a distance 

 of a mile along both shores of the narrow channel northwest 

 of Bremerton near Tracyton. To the north of these Oligocene 

 outcrops, the only formations within the county exposed at the 



