The Point Loma Formation is a sedimentary geological formation in Southern California

Southern California

Southern California is a megaregion, or megapolitan area, in the southern area of the U.S. state of California. Large urban areas include Greater Los Angeles and Greater San Diego. The urban area stretches along the coast from Ventura through the Southland and Inland Empire to San Diego...

. The strata date back to the Late Cretaceous

Late Cretaceous

The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...

. The formation is named after Point Loma

Point Loma, San Diego, California

Point Loma is a seaside community of San Diego, California. Geographically it is a hilly peninsula that is bordered on the west and south by the Pacific Ocean, the east by the San Diego Bay and Old Town and the north by the San Diego River...

, California.

Description

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

Fossils

The formation contains foraminifers

Foraminifera

The Foraminifera , or forams for short, are a large group of amoeboid protists which are among the commonest plankton species. They have reticulating pseudopods, fine strands of cytoplasm that branch and merge to form a dynamic net...

, mollusks

Mollusca

The Mollusca , common name molluscs or mollusksSpelled mollusks in the USA, see reasons given in Rosenberg's ; for the spelling mollusc see the reasons given by , is a large phylum of invertebrate animals. There are around 85,000 recognized extant species of molluscs. Mollusca is the largest...

, and coccolith

Coccolith

Coccoliths are individual plates of calcium carbonate formed by coccolithophores which are arranged around them in a coccosphere.- Formation and composition :...

s. These were used to date the formation biostratigraphically

Biostratigraphy

Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them. Usually the aim is correlation, demonstrating that a particular horizon in one geological section represents the same period...

.

Dinosaur

Dinosaur

Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

 remains have been recovered from this formation. In 1967 Brad Riney found a single hadrosaur

Hadrosaurid

Hadrosaurids or duck-billed dinosaurs are members of the family Hadrosauridae, and include ornithopods such as Edmontosaurus and Parasaurolophus. They were common herbivores in the Upper Cretaceous Period of what are now Asia, Europe and North America. They are descendants of the Upper...

 neck vertebra in a sea cave in La Jolla. In 1983 he found a femur

Femur

The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...

 of a hadrosaur in Carlsbad

Carlsbad, California

-2010:The 2010 United States Census reported that Carlsbad had a population of 105,328. The population density was 2,693.1 people per square mile . The racial makeup of Carlsbad was 87,205 White, 1,379 African American, 514 Native American, 7,460 Asian, 198 Pacific Islander, 4,189 from other...

 and in 1986 thirteen cervical vertebrae

Cervical vertebrae

In vertebrates, cervical vertebrae are those vertebrae immediately inferior to the skull.Thoracic vertebrae in all mammalian species are defined as those vertebrae that also carry a pair of ribs, and lie caudal to the cervical vertebrae. Further caudally follow the lumbar vertebrae, which also...

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

Ankylosauria

Ankylosauria is a group of herbivorous dinosaurs of the order Ornithischia. It includes the great majority of dinosaurs with armor in the form of bony osteoderms. Ankylosaurs were bulky quadrupeds, with short, powerful limbs. They are first known to have appeared in the early Jurassic Period of...

 Aletopelta

Aletopelta

Aletopelta coombsi was an ankylosaurian ornithischian dinosaur whose fossils were found in Southern California.Etymologically, the generic name is composed of the Greek terms aletes and pelte, meaning, respectively "wandering" and "shield"...

 coombsi. In about 1980 Leon Case found the midsection of a right dentary

Mandible

The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...

with teeth of a hadrosaur while walking along a beach in San Diego County.