Suites of samples collected from the Ardath Shale and Stadium Conglomerate, San Diego, California were analysed for benthonic foraminifera. The Ardath Shale contains a classic "Ulatisian" benthonic foraminiferal assemblage characterized by large percentages of Cyclammina, Reophax, Gyroidina, Bulimina, and Eponides. The benthonic assemblage suggests deposition of the Ardath Shale in upper middle bathyal water depths (600-1500 m). Planktonic foraminifera indicates an early Middle Eocene age.
A "Narizian" benthonic foraminiferal assemblage is characteristic of the Stadium Conglomerate. Arenaceous genera arc few in number (mainly Gaudryind). Species of Anomalina, Hanzawaia, Nonion, Melonis, and Cibicides dominate the benthonic fauna. Such a faunal composition is suggestive of inner shelf deposition (0-60 m). A late Middle Eocene age is indicated by planktonic foraminifera.