Type area designated near confluence of San Dieguito River and Lusardi Creek, secs.26-27 T13S R3W, southeastern Rancho Sante Fe 7.5' quad, San Diego Co, CA. Exposed over 25 sq mi area along northern margin of San Diego near Rancho Sante Fe, CA. Consists of massive cobble and boulder conglomerate; near western margin consists of reddish-brown sandstone with interbedded conglomerate lenses. Is over 400 ft thick. Unconformably overlies Late Jurassic to Early Cretaceous igneous and metamorphic rocks; unconformably underlies Eocene LaJolla Formation; in Carlsbad area unconformably underlies "Rosario" Formation (of Late Cretaceous age). Age is Early to middle Late Cretaceous (approximately 155 to 70 Ma) based on stratigraphic relations.
Source: GNU records (USGS DDS-6; Menlo GNULEX).
Lusardi Formation of Nordstrom (1970) adopted as lowermost formation (of 3) of Rosario Group (rank raised). In Carlsbad area conformably underlies Point Loma Formation (new) of Rosario Group. Age is Late Cretaceous based on stratigraphic relation to Point Loma Formation which contains Campanian foraminifers.
Source: GNU records (USGS DDS-6; Menlo GNULEX).
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