BORDERLAND

A Bouguer gravity anomaly map of the southern Calif-ornia Continental Borderland is presented. This is separated into regional and residual components. The regional anomaly shows an abrupt change from oceanic to continental structure at the Patton Escarpment, with a gradual thickening of the crust inland and a thinning under the Mojave Desert. The residual anomalies indicate several structural features and show gravity lows over many of the basins, indicating considerable deposition of sediments. Crustal models were calculated along two profiles. These show the presence of antiroots under the larger offshore basins, and a dip of at least 45 degrees at the continental margin-which could well be vertical. The general trend of the gravity anomalies in the Borderland is similar to the major structural trends of southern California, with a northwest-southeast trend in the Borderland terminating at the east-west trending Transverse Ranges. The gravity anomalies over the Transverse Ranges are small, and the combination of seismic and gravity data still leads to ambiguous interpretation of the crust under the mountains