Forty-one K-Ar dates are reported from the Coast Ranges of California, Oregon, and Washington, and from Santa Cruz and San Clemente Islands, California. The following radiometric ages are indicated for Pacific Coast Foraminiferal Stage boundaries: Zemorrian\Saucesian ≈22.5 m.y.; Saucesian\Relizian ≈15.3 m.y.; Relizian\Luisian, 13.7 to 14.5 m.y.; Luisian\Mohnian, less than 13 m.y. The following radiometric correlations are indicated between Pacific Coast Foraminiferal Stages and North American Land-Mammal Ages (Table 1):

Fourteen dates are reported which are stratigraphically related to age-diagnostic marine megafossil assemblages. Radiometric correlation of Pacific Coast Megafossil “Stages” with other chronologies is not attempted because doubt remains as to whether or not these “Stages” represent time-stratigraphic units. Problems associated with dating volcanic glass shards by the K-Ar method are discussed.