Stratigraphic Relations of Upper Cretaceous and Eocene Formations, San Diego Coastal Area, California

ABSTRACT This paper defines three Upper Cretaceous formations exposed in and near San Diego, California. The lowest, which consists of boulder conglomerate, is the previously named Lusardi Formation; the intermediate, which consists of siltstone and sandstone, is the Point Loma Formation (new name); and the uppermost, which consists of sandstone and conglomerate, is the Cabrillo Formation (new name). Together these constitute the Rosario Group, redesignated from its former rank as a formation. Eight partly intertonguing Eocene formations also are defined. Of these, six have new names and two are former members raised in rank to formational status. The lowest of the Eocene formations is the Mount Soledad Formation (new name), a marine conglomerate and sandstone unit occurring in the western part of the area. Above and northeast of the Mount Soledad Formation are the laterally equivalent Delmar Formation and Torrey Sandstone (both raised here from member to formational rank) and the Ardath Shale (new name). The Delmar Formation is an oyster-bearing sandy claystone, the Torrey Sandstone is a massively crossbedded sandstone, and the Ardath Shale is a fossiliferous silty shale. Overlying and partly intertonguing with these formations is the Scripps Formation (new name), composed of sandstone, siltstone, and conglomerate, and overlying the Scripps is the chiefly nonmarine Friars Formation (new name), which consists of sandstone and sandy claystone. All these Eocene rocks were formerly included in the La Jolla Formation, which is here elevated to group status. The remaining part of the Eocene section in the group status Diego area, above the La Jolla Group, was formerly called the Poway Conglomerate and is here elevated to group status, and two new formations are designated in its lower part. The lower, which consists of cobble conglomerate. Is the newly named Stadium Conglomerate; the upper, which consists chiefly of marine sandstone and siltstone, is the newly named Mission Valley Formation.