Table 1. Clastic sedimentary rock classification and characteristics.
Rock Name Clast Size Associated Rock Formations at Cabrillo National Monument
Conglomerate (rounded clasts)
or breccia (angular clasts)
greater than 2 mm (0.08 in) Cabrillo Formation (Kccg)
Rosario Group (Kuo)
Sandstone 1/16–2 mm (0.0025–0.08 in) Cabrillo Formation (Kcs)
Point Loma Formation (Kp)
Rosario Group (Kuo)
Siltstone 1/256–1/16 mm (0.00015–0.0025 in) Point Loma Formation (Kp)
Rosario Group (Kuo)

carrying on h2.

The most unusual fossil found in the Point Loma Formation at the monument to date was a large cycad leaf (fig. 14). It was discovered at the tidepool area and is now on display at the San Diego Natural History Museum (Koch and Santucci 2003; Tweet et al. 2012). This specimen has not been formally described in the literature. Other interesting finds in the Point Loma Formation, though not from within the monument, are large ammonites with epibiont (an organism that is attached to and lives on the surface of another organism) thorny oysters, and a partial tooth of a mosasaur (giant marine lizard) (see scoping summary by KellerLynn 2008a). Of possible interest for interpretation, the Point Loma Formation yielded Aletopelta coombsi—the first dinosaur named from California. It is either an ankylosaurid (Ford and Kirkland 2001) or a nodosaurid (Coombs and Deméré 1996; Hawakaya et al. 2005). The Point Loma Formation in the monument has yet to yield a dinosaur fossil, but scoping participants mentioned a dinosaur fossil having been found in the Point Loma Formation at nearby Palomar Airport; that specimen is probably Aletopelta (Justin Tweet, NPS Geologic Resources Division, associate, written communication, 10 January 2017).

Cabrillo Formation

The Cabrillo Formation consists of mostly massive (lacking sedimentary structures) medium-grained sandstone (Kcs) and cross-bedded (composed of strata inclined at an angle) cobble conglomerate (Kccg) (fig. 15). The type section for the Cabrillo Formation is in the sea cliffs 250 m (820 ft) east of the new Point Loma lighthouse (Point Loma Light Station), where the base of the formation is 30 m (100 ft) above mean sea level and the top of the formation is at the top of the cliff (Kennedy and Moore 1971). About 81 m (266 ft) of the formation is exposed in the type section (fig. 4). Elsewhere, even greater thicknesses are exposed; for example, in the False Point sea cliff at Bird Rock, north of the monument, the exposure is 170 m (560 ft) thick (Kennedy and Tan 2008).
The Cabrillo Formation does not contain as rich a fossil record as the Point Loma Formation, but has yielded wood fragments, coral, brachiopods, bivalves, ammonites, gastropods, and echinoderms from a series

Last updated: May 3, 2018