The Eagle Rest Peak igneous complex in the San Emigdio Mountains, and Logan gabbro, near San Juan Bautista, California, crop out on opposite sides of the San Andreas fault. They have identical U-Pb zircon ages of 161 Ma and similar Sr initial isotopic ratios. These data support previous correlations of these rocks (Ross, 1970) and require 305 km of post-Jurassic slip on the northern San Andreas fault, a figure equal to the total slip on the southern segment. The Eagle Rest Peak complex has previously been proposed as the source for gabbro clasts in the Upper Cretaceous Gualala Formation near Point Arena (Ross, 1970; Ross and others, 1973). This implies >440 km of post-Late Cretaceous slip on the San Andreas fault and the existence of a proto-San Andreas fault. Also, granitic to quartz dioritic clasts in the Gualala Formation have been interpreted as detritus derived from the Salinian block in the Cretaceous. However, new U-Pb zircon data from Gualala Formation gabbroic clasts indicate minimum ages of 163 and 165 Ma, slightly older than the 161-Ma age of the Eagle Rest Peak complex and Logan gabbro. Published K-Ar ages also suggest the Gualala cobbles are older than the Eagle Rest Peak complex. These data and the presence of alternate sources for the Gualala cobbles indicate that the Gualala-Eagle Rest Peak tie is not suitable for determining slip on the San Andreas fault. Despite the differences between specific areas, the Eagle Rest Peak complex, Gold Hill and Logan gabbros, and the Gualala gabbro clasts are similar in age and lithology to mafic-ultramafic complexes that form a widespread part of the Jurassic Sierran-Klamath arc. Although Gualala gabbro clasts cannot be uniquely matched to the Eagle Rest Peak complex and Logan rocks, they probably are derived from similar rocks cropping out in the Sierra foothills or buried in the Great Valley. U-Pb-age, Sr, and Pb isotopic data from a single Gualala Formation granodiorite clast do not support a Salinian provenance. The clast is older than 154 Ma, older than the 80- to 120-Ma Salinian granites. The clast also has less radiogenic Pb and Sr isotopic ratios than plutonic rocks from the Salinian block. A reevaluation of paleocurrent data and clast types from the Gualala Formation also suggests a non-Salinian source. The Gualala area is apparently not part of the Salinian block.