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Chico Formation facts for kids

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Chico Formation
Stratigraphic range: Campanian Age,
Cretaceous Period
Type Geological formation
Underlies Martinez Formation (regionally),
Tejon Formation (regionally)
Overlies Vaqueros Formation
Primary sandstone
Region California, Oregon
Country United States
Type section
Named for Chico, California

The Chico Formation is a geologic formation of the Campanian Age during the Cretaceous Period, found in California and southern Oregon.


The Cenozoic Era formation can regionally overlie the Vaqueros Formation, and can regionally underlie the Martinez Formation or Tejon Formation.

The Chico Formation is exposed in the Southern California Coast Ranges, western San Joaquin Valley, north of Mount Diablo, and in the Chico area of the northeastern Sacramento Valley.

It is also found in the eastern Simi Hills in Bell Canyon and Dayton Canyon, located in Los Angeles and Ventura Counties, near the community of West Hills.


Dinosaur remains are among the fossils that have been recovered from the formation, from the Late Cretaceous of the Mesozoic Era.


The lizard and bird species listed in the table below date from the Late Cretaceous Epoch.

Vertebrates of the Chico Formation
Genus Species Location Member Abundance Notes Images




indet. Pteranodontidae

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