Abstract
The integration of calpionellid biostratigraphy, microfacies analysis, UPb geochronology, and strontium chemostratigraphy improves the definition of the Berriasian–Valanginian boundary in the Tlatlauquitepec area and validates the age of calpionellid zones from eastern Mexico in this interval. An age of 139.85 Ma derived from 87Sr/86Sr ratio within the base of Calpionellites Zone defines the Berriasian–Valanginian boundary. Additionally, the 134.0 ± 0.5 Ma UPb age returned by zircon grains from a tuff level exposed at the top of the succession confirms the Valanginian age of the whole analyzed section. Microfacies analysis reveals sea level variations that can be coincident with the KVa1–KVa4 eustatic cycles. These new data suggest that calpionellid biostratigraphy represents the most useful tool for the definition of the Berriasian–Valanginian time boundary in central Mexico and its correlation with the rest of the Tethyan domain.
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