Chico Creek (Big)
Map SatelliteBig Chico Creek in this section of its course, which includes 3 kilometers (2 miles) in Bidwell Park and upstream another 8 kilometers (5 miles), has cut a deep gorge some 150 meters (500 feet) deep. In places, the upper walls of the gorge are vertical.
This is the type locality for the Chico Formation which is an Upper Cretaceous clastic marine sedimentary formation that here forms a series 600 meters (2,000 feet) thick. It rests unconformably on older Sierra metamorphics and is overlain by Tertiary volcanics. The fauna exposed in these beds is quite abundant and includes various cephalopods, pelecypods and gastropods. At one time this series was correlated with most of the Upper Cretaceous rocks in the Great Valley area; however, recent studies have named a number of new formations, faunal zones, and members.
Vegetation is oak woodland and chaparral, with some riparian.
The creek is permanent.
Integrity: Portions of the valley floor have been developed as a park, and there are ranches and a road in the area.
Use: Educational, research, light recreational in public portion.
Ref: Taff, J. A., G. D. Hanna and C. N. Cross, 1940. Type Locality of the Cretaceous Chico Formation. Geo. Soc. of Amer. Vol. 51, pp. 1311-1327.
October 1975
Inventory of California Natural Areas
Revision © 2009 Steven Louis Hartman