High-resolution stratigraphy of buchiid bivalves and ammonites from the Jurassic–Cretaceous boundary beds in the Paskenta area (California)

A bed-by-bed biostratigraphical study of two key Californian outcrop sections of the Jurassic–Cretaceous transition interval is presented. The studied succession is characterized by the occurrence of abundant buchiid bivalves and a discontinuous ammonite record. Several Lower Cretaceous ammonite zones were introduced in the literature, but the precise stratigraphic position of key ammonite records remains unclear. Consequently, the buchiid...