Physical and faunal data suggest the presence of a previously unrecognized regional stratigraphic discontinuity within the Lower Cretaceous succession of northern California and Oregon. Rocks above the discontinuity are of Aptian and Albian ages and include the "upper Shasta," the Huling and Upper Chickabally Members of the Budden Canyon Formation, and the Albian strata at Horsetown, Grave Creek, and Mitchell. Rocks below the discontinuity, some as young as Barremian, differ considerably in age and type and, in addition to a variety of pre-Cretaceous units, include the Days Creek Formation, the Humbug Mountain Conglomerate and Rocky Point Formation, the Rector, Ogo, Roaring River, and Lower Chickabally Members of the Budden Canyon Formation, and the "lower Shasta." Magnit de of the lacuna differs greatly from place to place, from less than a stage to more than a system. Apparently this discontinuity reflects widespread mid-Early Cretaceous diastrophism; the break can be recognized through the entire region and may extend well beyond.