Palynological and biostratigraphical contributions to the stratigraphic understanding of Pliocene-Pleistocene deposits in the Cap Bon area (northeast Tunisia)

The CNH (Coupe Nabeul Houwaria) sedimentary succession (Cap Bon, NE Tunisia) was previously attributed to the Piacenzian-Gelasian transition based on preliminary micropaleontological data. This study re-evaluates that hypothesis through an integrated stratigraphic approach that combines calcareous nannofossils, planktonic foraminifera, and palynological data. Calcareous nannofossil assemblages are dominated by Reticulofenestra and Sphenolithus, with the consistent presence of Reticulofenestra pseudoumbilicus >7 μm and the absence of Quaternary marker taxa, constraining the succession to no younger than 3.82 Ma (top of Zone CNPL3). Palynological evidence, including subtropical to warm-temperate vegetation and dinoflagellate cyst assemblages lacking cold indicators, supports a warm climate incompatible with glacial conditions. This interpretation is further reinforced by the absence of Bythocythere turgida, an ostracod known as a significant “Northern guest”. The presence of Globorotalia puncticulata restricts the maximum age of the succession to no older than its first occurrence at ca. 4.52 Ma, while the absence of Globorotalia margaritae suggests even an age younger than 3.98 Ma (its last common occurrence). Taken together, these data frame the CNH succession within a time interval between ca. 4.52 (or 3.98 Ma) and 3.82 Ma, indicating a late Zanclean age and calling for a substantial revision of its lithostratigraphic assignment. The study highlights the need for high-resolution, multi-proxy analyses and, in particular, future magnetostratigraphic investigations, to improve regional chronostratigraphic models in NE Tunisia and strengthen correlations with the global stratigraphic framework.