Upper Cretaceous dinoflagellate cysts events from the sub-tropical northern hemisphere

Abstract

Recognizing the ranking optime sequence of fossil dinoflagellate cysts can be a challenge for qualitative biostratigraphy. For this reason, we present the result of a quantitative stratigraphic study through probabilistic analysis of six wells from Baja California (Mexico) and six from the Gulf of Suez and the Mediterranean Sea (Egypt), which allows us to recognize 22 species of dinoflagellate cysts in an optimal sequence with 95% probability for the Upper Cretaceous in subtropical areas of the Northern Hemisphere. Photoautotrophic species represent the largest number in the database (159 species), indicating that they are the main producers, while heterotrophic species are in the minority (74 species). Spiniferites and Florentinia are the most abundant and diverse taxa, which, together with the absence of the genus Impagidinium, indicates a shallow marine depositional environment. The quantitative analysis estimates an optimal classified succession that allows the Upper Cretaceous to be divided into five groups (G1 to G5) of species communities with similar ages. The greatest species diversity is found in group G4, associated with the Maastrichtian, and the least in group G1, associated with the early Cenomanian to early Turonian. These results and comparison with previous studies using the same method of quantitative biostratigraphy suggest a similarity of paleoenvironmental conditions in subtropical regions of the Northern Hemisphere and tropical regions during the Upper Cretaceous.