EVIDENCE OF A PALYNOLOGICAL BIOEVENT MARKING THE CRETACEOUS-PALEOGENE (K-PG) BOUNDARY IN THE OFFSHORE BASIN OF CÔTE D’IVOIRE (WEST AFRICA)

The reliable recognition of the Cretaceous - Paleogene (K-Pg) boundary is a major concern in applied biostratigraphy, especially in petroleum basins where this boundary constrains the calibration of major regional unconformities. This study examines, based on six exploration wells from the offshore Côte d’Ivoire basin (OB-1X, OB-3X, OB-6X, OB-4X, OB-5X and OB-2X, distributed across blocks B4, A7 and C02), the reproducibility of a single palynological bioevent: the joint first downhole occurrence of the dinoflagellates Cerodinium granulostriatum and Andalusiella gabonensis. This bioevent marks the K-Pg boundary in all six studied wells, consistently bracketed downhole by a characteristic Paleocene assemblage dominated by other dinocyst associations, and, further downhole, by the Maastrichtian Andalusiella assemblage sensu lato. A detailed, well-by-well analysis of the palynological succession across this boundary shows remarkable consistency in the taxa involved and their relative order of appearance. This exceptional robustness, discussed in light of the globally non-extinctive but strongly reorganised dinocyst assemblage behaviour documented at international reference K-Pg sections, as well as in light of previous work on the Ivorian margin, gives this bioevent a first-order value for regional correlation and petroleum exploration.