Article · Wikipedia archive · Last revised Jun 23, 2026

Chico Formation

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

Last revised
Jun 23, 2026
Read time
≈ 1 min
Length
316 w
Citations
11
Source
Chico Formation
Stratigraphic range: Campanian Age,
Cretaceous Period
TypeGeological formation
UnderliesMartinez Formation (regionally),
Tejon Formation (regionally)
OverliesVaqueros Formation
Lithology
Primarysandstone
Location
RegionCalifornia, Oregon
CountryUnited States
Type section
Named forChico, California

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

Geology

The MesozoicEra 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.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

Paleofauna

Dinosaur remains are among the fossils that have been recovered from the formation, from the Late Cretaceous of the Mesozoic Era.12

Species

The lizard and bird species listed in the table below date from the Late Cretaceous Epoch.134

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

Clidastes5

Hesperornis source ↗

Hesperornis6

Ichthyornis6

indet. Pteranodontidae7

See also

See also

References

References

  1. Google Books: "The stratigraphic and faunal relations of the Martinez formation to the Chico and Tejon of Southern California", Clarence A. Waring; Stanford University Dept. of Geology; Jun 4, 2011 . accessed 1.16.2016.
  2. Weishampel, et al. (2004). "Dinosaur distribution." Pp. 517-607.
  3. Hilton, Richard P. 2003. Dinosaurs and Other Mesozoic Reptiles of California. Berkeley: University of California Press. 318 pp.
  4. Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. 861 pp. ISBN 0-520-24209-2.
  5. Listed as "Clidastes?" in "Appendix: Summary of the Mesozoic Reptilian Fossils of California," Hilton (2003) p. 274
  6. "Appendix: Summary of the Mesozoic Reptilian Fossils of California," in Hilton (2003) p. 273
  7. "Zitterliana" (PDF).