San Francisquito Formation
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The San Francisquito Formation is a
geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...
located in northern
Los Angeles County Los Angeles County, officially the County of Los Angeles and sometimes abbreviated as LA County, is the most populous county in the United States, with 9,663,345 residents estimated in 2023. Its population is greater than that of 40 individua ...
,
California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...
. Seismo.berkeley.edu: Field Guide to the Punchbowl Fault Zone, at Devil's Punchbowl Los Angeles County Park
San Andreas Fault Resources; University of California, Berkeley; by Frederick M. Chester; January 1999.

Department of Earth Sciences, University of California, Riverside; 1982.
Areas where it is exposed include:
San Francisquito Canyon San Francisquito Canyon is a canyon created through erosion of the Sierra Pelona Mountains by the San Francisquito Creek, in Los Angeles County, Southern California. Geography The canyon cuts through the Sierra Pelona Mountains, which are central ...
of the
Sierra Pelona Mountains The Sierra Pelona, also known as the Sierra Pelona Ridge or the Sierra Pelona Mountains and originally known as the Liebre Mountains, is a mountain ridge in the Transverse Ranges in Southern California. Located in northwest Los Angeles County, t ...
, as well as on the northwestern side of the
Devil's Punchbowl The Devil's Punch Bowl is a visitor attraction and biological Site of Special Scientific Interest situated just to the east of the village of Hindhead in the English county of Surrey. It is part of the Wealden Heaths Phase II Special Protection ...
gorge in the
San Gabriel Mountains The San Gabriel Mountains () are a mountain range located in Los Angeles and San Bernardino counties, California, United States. The mountain range is part of the Transverse Ranges and lies between the Los Angeles Basin and the Mojave Desert ...
.


Geology

The San Francisquito Formation consists of marine deposits that originated during the
Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent 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 ''cre ...
period of the
Mesozoic Era The Mesozoic Era is the era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Periods. It is characterized by the dominance of archosaurian reptiles such as the dinosaurs, and of gymnosperms s ...
, and the Early Paleocene epoch (geology), epoch in the Paleogene Period (geology), period of the Cenozoic Era. It is overlain by the Punchbowl Formation (east) and Castaic Formation (west), both of the Miocene and Pliocene epochs. It overlies the crystalline San Gabriel Basement Complex. It is found between the San Andreas Fault on its north, and the Devil's Punchbowl Fault on its south. The Pliocene epoch Crowder Formation is to the northeast.


Fossil content

It preserves fossils dating back to the Paleogene Period (geology), period.


See also

* * List of fossiliferous stratigraphic units in California * Paleontology in California * Neenach Volcano


References

Geologic formations of California Cretaceous California Paleogene California Maastrichtian Stage of North America Danian Stage Cretaceous–Paleogene boundary Shale formations of the United States Geology of Los Angeles County, California San Gabriel Mountains Sierra Pelona Ridge {{Paleogene-stub