Dinoflagellate cysts, palynofacies and organic geochemistry of the Cretaceous-Palaeogene (K–Pg) boundary transition at the Ellès section, northeastern Tunisia

Amel M’Hamdi, Hamid Slimani, Kmar Ben Ismail-Lattrache, Walid Ben Ali


A palynofacies study carried out across the Cretaceous–Palaeogene (K–Pg) boundary in the El Haria Formation at Ellès, northeastern Tunisia, revealed the presence of organic matter dominated by marine palynomorphs, mainly dinoflagellate cyst assemblages. Continental palynomorphs (sporomorphs) and amorphous organic matter (AOM) are also present in all samples. The total organic carbon (TOC) content is generally less than 0.7 wt.%. The Rock-Eval S1 parameters vary from 0.01 to 0.3 mgHC/g rock. The Rock-Eval S2 parameters vary from 0.15 to 0.57 mgHC/g rock. The hydrogen index (HI) and oxygen index (OI) values range from 61 to 214 mgHC/g TOC and 149 to 638 mgHC/g TOC, respectively. The Tmax values range from 420 to 440°C. The TOC, Rock-Eval pyrolysis and palynofacies analyses indicate that the El Haria Formation is characterized by immature organic matter type II and III and a low thermal alteration index (TAI). Also, the authors present in this paper the biostratigraphic, palaeoenvironmentl and palaeobiogeographic framework for the dinoflagellate cyst assemblages below and above the Cretaceous–Palaeogene boundary in the Ellès section.

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