In the western part of the La Jolla 15-minute quadrangle, Upper Cretaceous and Cenozoic sediments lie upon the eroded surface of older basement rock. A pattern of gravity stations was established to determine the depth to and configuration of the top of the basement rocks. Contours of cravity anomalies were found to parallel axes of probable folds. In the Mission Bay area the anomalies indicate a depth of about 3,000 feet to basement, while beneath Soledad Mountain they reveal a more shallow depth of about 1,500 feet. North of Soledad Mountain the depth to basement increases, reaching 2,500 feet at a gravity low near Carmel Mountain. This trend reverses itself northeast of Del }!,'ar.