San Francisquito Formation

San Francisquito Formation
Stratigraphic range: Maastrichtian-Danian ~70–62  Ma PreꞒ Ꞓ O S D C P T J K Pg N
Type	Geologic formation
Underlies	Castaic & Punchbowl Formations
Overlies	San Gabriel Basement Complex
Thickness	4 km (13,000 ft)
Lithology
Primary	Sandy shale
Location
Coordinates	34°36′N118°36′W / 34.6°N 118.6°W / 34.6; -118.6
Approximate paleocoordinates	39°30′N96°30′W / 39.5°N 96.5°W / 39.5; -96.5
Region	Los Angeles County, California
Country	United States
Extent	San Gabriel Mountains & Sierra Pelona Mountains
San Francisquito Formation (the United States) Show map of the United States San Francisquito Formation (California) Show map of California

The San Francisquito Formation is a geologic formation located in northern Los Angeles County, California. ^{[1] [2]}

Areas where it is exposed include: San Francisquito Canyon of the Sierra Pelona Mountains, as well as on the northwestern side of the Devil's Punchbowl gorge in the San Gabriel Mountains. ^{[1] [2]}

Geology

The San Francisquito Formation consists of marine deposits that originated during the Late Cretaceous period of the Mesozoic Era, and the Early Paleocene epoch in the Paleogene period of the Cenozoic Era. ^{[1] [2]} It is overlain by the Punchbowl Formation (east) and Castaic Formation (west), both of the Miocene and Pliocene epochs. ^[1] It overlies the crystalline San Gabriel Basement Complex. ^[1]

It is found between the San Andreas Fault on its north, and the Devil's Punchbowl Fault on its south. ^{[1] [2]} The Pliocene epoch Crowder Formation is to the northeast. ^[1]

Fossil content

It preserves fossils dating back to the Paleogene period. ^[3]

See also

• Geology of Los Angeles County, California
• List of fossiliferous stratigraphic units in California
• Paleontology in California
• Neenach Volcano

References

1. 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.
2. AAPG Datapages/Archives: "Stratigraphy and Sedimentology of the Type San Francisquito Formation, Southern California"; Department of Earth Sciences, University of California, Riverside; 1982.
3. Various Contributors to the Paleobiology Database. "Fossilworks: Gateway to the Paleobiology Database". Archived from the original on 19 August 2022. Retrieved 17 December 2021.