| Point Loma Formation Stratigraphic range: Late Cretaceous |
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|---|---|
Typical exposure of the Point Loma Formation at Sunset Cliffs |
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| Type | Geological formation |
| Unit of | Rosario Group |
| Underlies | Cabrillo Formation |
| Overlies | Lusardi Formation |
| Thickness | 400 m |
| Lithology | |
| Primary | sandstone, shale, siltstone |
| Location | |
| Named for | Point Loma |
| Named by | Kennedy and Moore, 1971[1] |
| Region | North America |
| Country | United States |
| Extent | San Diego to La Jolla |
The Point Loma Formation is a sedimentary geological formation in Southern California. The strata date back to the Late Cretaceous. The formation is named after Point Loma, California.
Contents |
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.[1]
The formation contains foraminifers, mollusks, and coccoliths.[1] These were used to date the formation biostratigraphically.
Dinosaur remains have been recovered from this formation.[2] In 1967 Brad Riney found a single hadrosaur neck vertebra in a sea cave in La Jolla. In 1983 he found a femur of a hadrosaur in Carlsbad and in 1986 thirteen cervical vertebrae of another hadrosaur. In 1987 Riney discovered teeth and fragments of the postcranium of the ankylosaur Aletopelta coombsi.[3] In about 1980 Leon Case found the midsection of a right dentary with teeth of a hadrosaur while walking along a beach in San Diego County.[4]