The Forbes Shale is a geologic formation in the Sacramento Valley of northern California, including the Sutter Buttes area. It preserves fossils from the Coniacian stage of the Late Cretaceous, including bivalves, gastropods, and ammonites, showing that marine life existed when these sediments were deposited. Its importance rests in this fossil record, which helps document California’s Late Cretaceous environments and adds to the region’s deep geologic history.