Physical and faunal relations in the Upper Cretaceous (Turonian-Senonian) of northern California and Oregon suggest the presence of a major widespread stratigraphic discontinuity. Rock units above the discontinuity include an unnamed unit on the southwestern Oregon coast, the upper part of the Hornbrook Formation (including so-called "Umpqua"), the upper part of the Redding Formation, the type Chico Formation, the Guinda and Forbes Formations (including "Funks" of the Putah Creek section), and the Gualala and Yager Formations. Rock units below the discontinuity range widely in type and age and include crystalline rocks of the Sierra Nevada-Klamath Mountains belt, Franciscan rocks, the Myrtle Group (Upper Jurassic and Lower Cretaceous), and a variety of Cretaceous units, s me possibly as young as Coniacian. Magnitude of the lacuna ranges considerably, from some areas where it appears to be very small (judged by present correlations) to other areas where a period or more is involved. This widespread stratigraphic break is believed to be related to the "Coast Range orogeny," a Late Cretaceous deformational episode proposed recently by Irwin.