Flows and flow breccia of basaltic andesite and lesser diktytaxitic to intergranular olivine basalt. Includes some dense, aphyric flows, commonly with either cryptocrystalline or pilotaxitic to trachytic texture, and porphyritic flows with phenocrysts and glomerocrysts of olivine, hypersthene, and labradorite. A few flows contain both hypersthene and calcic augite phenocrysts. Olivine mostly fresh or slightly altered to iddingsite in flows high in section; flows low in section show some alteration to clays (nontronite and saponite), secondary silica minerals, and calcite; pinkish-brown glass in some flows unaltered. Locally includes some andesite and dacite. Some flows of this unit are lithologically similar to flow rocks of the High Cascade volcanic sequence and some are more like flows that in the past have been mapped as part of the Sardine Formation (Peck and others, 1964) and Elk Lake Formation of McBirney and others (1974) and Sutter (1978). Potassium-argon ages of rocks from this unit range from about 4 to 8 or 9 Ma. Includes some rocks formerly mapped as Rhododendron Formation by Peck and others (1964)