The Point Loma Formation is a

sedimentary Sedimentary rocks are types of rock (geology), rock that are formed by the accumulation or deposition of mineral or organic matter, organic particles at Earth#Surface, Earth's surface, followed by cementation (geology), cementation. Sedimentati ...

geological

formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondar ...

Southern California Southern California (commonly shortened to SoCal) is a geographic and Cultural area, cultural region that generally comprises the southern portion of the U.S. state of California. It includes the Los Angeles metropolitan area, the second most po ...

. The strata date back to the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...

epochs of the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

period, during the

Mesozoic Era The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising ...

. The formation is named after the

Point Loma Point Loma (Spanish: ''Punta de la Loma'', meaning "Hill Point"; Kumeyaay: ''Amat Kunyily'', meaning "Black Earth") is a seaside community within the city of San Diego, California. Geographically it is a hilly peninsula that is bordered on the w ...

peninsula in southwestern

San Diego County, California San Diego County (), officially the County of San Diego, is a county in the southwestern corner of the U.S. state of California. As of the 2020 census, the population was 3,298,634, making it California's second-most populous county and the fi ...

Description

The Point Loma Formation was first described as the middle formation of the Rosario

Group A group is a number of persons or things that are located, gathered, or classed together. Groups of people * Cultural group, a group whose members share the same cultural identity * Ethnic group, a group whose members share the same ethnic ide ...

by Kennedy and Moore in 1971. Their description is that the lower half is composed of interbedded fine-grained, dusky yellow sandstone and olive-gray clay shale in ledgy graded beds about 20 cm thick, which grades into massive grayish-black siltstone in the top half of the formation. Part of the Rosario Group, it overlies the Lusardi Formation, and underlies the Cabrillo Formation. The formation is found from Point Loma north to

La Jolla La Jolla ( , ) is a hilly, seaside neighborhood within the city of San Diego, California, United States, occupying of curving coastline along the Pacific Ocean. The population reported in the 2010 census was 46,781. La Jolla is surrounded on ...

, within the city of

San Diego San Diego ( , ; ) is a city on the Pacific Ocean coast of Southern California located immediately adjacent to the Mexico–United States border. With a 2020 population of 1,386,932, it is the List of United States cities by population, eigh ...

Fossils

The formation contains

foraminifers Foraminifera (; Latin for "hole bearers"; informally called "forams") are single-celled organisms, members of a phylum or class of amoeboid protists characterized by streaming granular ectoplasm for catching food and other uses; and commonly an ...

mollusks Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...

, and

coccolith Coccoliths are individual plates or scales of calcium carbonate formed by coccolithophores (single-celled phytoplankton such as ''Emiliania huxleyi'') and cover the cell surface arranged in the form of a spherical shell, called a ''coccosphere''. ...

s. These were used to date the formation biostratigraphically.

Dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

remains have been recovered from this formation.Weishampel, David B; et al. (2004). "Dinosaur distribution (Late Cretaceous, North America)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 574-588. . In 1967 Brad Riney found a single

hadrosaur Hadrosaurids (), or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. The ornithopod family, which includ ...

neck vertebra in a

sea cave A sea cave, also known as a littoral cave, is a type of cave formed primarily by the wave action of the sea. The primary process involved is erosion. Sea caves are found throughout the world, actively forming along present coastlines and as relic ...

. In 1983 he found a

femur The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with ...

of a hadrosaur in Carlsbad and in 1986 thirteen

cervical vertebrae In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In ...

of another hadrosaur. In 1987 Riney discovered teeth and fragments of the postcranium of the ankylosaur ''

Aletopelta ''Aletopelta'' (; meaning 'wanderer shield') is a monospecific genus of basal ankylosaurid dinosaur from Southern California that lived during the Late Cretaceous (upper Campanian stage, 75.5 Ma) in what is now the Point Loma Formation. The type ...

coombsi''."Table 17.1," in Weishampel, et al. (2004). Page 368. In about 1980 Leon Case found the midsection of a right

dentary In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...

with teeth of a hadrosaur while walking along a beach in San Diego County.Hilton (''Dinosaurs and Other Mesozoic Reptiles of California'', 2003), pp. 233-36.

Description

Fossils

See also

References

Further reading