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.
[1] 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.
[1] Dinosaur remains are among the fossils that have been recovered from the formation, from the Late Cretaceous of the Mesozoic Era.
[1][2] The lizard and bird species listed in the table below date from the Late Cretaceous Epoch.
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