The middle and late Eocene Friars Formation (part of the Rose Canyon Shale Member of Hanna, 1926) is the uppermost unit of the La Jolla Group. The rocks are nonmarine and lagoonal sandstone and claystone named for exposures along the north side of Mission Valley near Friars Road in the La Jolla quadrangle (Kennedy and Moore, 1971a). The sandstone is composed of quartz (75 -80 percent), potassium feldspar (10-15 percent), biotite (5-10 percent), plagioclase (less than 1 percent), and a trace of amphibole, pyroxene, hematite, and tourmaline. The claystone is composed of montmorillonite and kaolinite. Friars Formation is predominantly a nonmarine and nearshore marine facies which reaches a maximum thickness of 50 m between Mission Valley and Carmel Valley. The sandstone is typically massive, yellowish gray, medium grained, and poorly indurated with subangular to subrounded grains. Caliche-rich sandstone beds are locally interlayered with dark greenish-gray sandy clays tone. Cobble conglomerate lenses and tongues of fluviatile origin are characteris tic of the easternmost exposures. The Friars Formation rests unconformably on rocks of the basement complex and conformably on the Scripps Formation. It is in turn overlain by other sedimen- Mission Valley Formation tary deposits of Eocene, Pleistocene, and Holocene The Mission Valley Formation, a predominanage. The Friars and Delmar Formations are tly marine sandstone unit, lies conformably upon the lithologically identical in their central and north Stadium Conglomerate and is in turn conformably the eastern exposures, and they have been un-overlain by the Pomerado Conglomerate. It has a differentiated in these areas on the geologic map.

Source - Geology of the eastern San Diego metropolitan area, California (Del Mar, La Jolla, Point Loma, La Mesa, Poway, and SW 1/4 Escondido quadrangles), 1975, California Div. Mines and Geol. Bull. 200, Section A, by Michael P. Kennedy

References

Hanna, M.A., 1926, Geology of the La Jolla quadrangle, California: University of California, Dept. Geol. Sci. Bull., v. 16, p. 1 87-246.
Kennedy, M.P., and Moore, G.W., 1971a, Stratigraphic relations of upper Cretaceous and Eocene formations, San Diego coastal area, California: American Assoc. Petroleum Geologists Bull., v. 55, p. 709-722.