Late Devonian Kellwasser Bioevent at Echouech Borehole (EC-1) Southern Tunisia

To identify and characterise the Kellwasser event in southern Tunisia, which is the subject of this study, we revised the biostratigraphy of the Echouech cores from the late Devonian, particularly Frasnian-Famennian transition. This interval is characterised by diversified fauna. The analysis of ostracod evolution enabled us to identify evidence of Kellwasser events associated with changes in environmental conditions, variations in oxygenation levels characterized by the presence of Buchiola and small pyritized ammonoids, a reduction in biodiversity, and the extinction of pelagic ostracods, Styliolina, and conodonts. Kellwaser event is marked by black shale horizons in the EC-1 borehole. Geochemical analysis of these horizons confirms the richness of organic matter and the reducing conditions at the base or top of the Frasnian. These horizons are rich in organic matter, reflecting generalized marine anoxia in the EC-1 borehole. A comparison of this event with other boreholes and with the stratotype section was carried out to determine its geographical extension.