One of Bidwell Park’s most unique features is its geology. Lower Bidwell Park occupies an alluvian flood plain which covers most of Chico. The rich deep soils are what give Chico and Bidwell Park the ability to grow massive tree canopy and make orchards viable. This geologic feature is not readily apparent to Park users.
Upper Bidwell Park’s geologic features really make Upper Park the place that it is. From the bottom of Big Chico Creek the Lovejoy Basalt volcanic rock rises sharply to where it is capped by the Tuscan formation. Cliff rise hundreds of feet and frame the Big Chico Creek canyon. Many call this area the “Little Grand Canyon”.
Chico Formation Fossil Rock – end of Upper Park Road – T. Barrett
Underlying the volcanic area is the Chico Formation. This formation was the floor of a great inland sea. It in underneath the entire Sacramento Valley pops up in only a couple places, most notably at the end of Upper Park road where people noticed there was a “salt lick” visited by deer and other animals. Water still travels through this sea floor. Another give-away of this formation are the fossil-laden rocks that can be found in this area.
A short video was produced by CSU Chico’s Geology Department and can be seen here.
Geology of Bidwell Park: An Outline Summary by Philip A. Lydon
Upper Bidwell Park Soils (pdf) courtesy of Andrew Conlin, of the Chico Soil Survey Office, Natural Resources Conservation Service, and Judy Stolen, at Upstate CA Planning and GIS