(U-Th)/He dating of supergene iron (oxyhydr-)oxides of the Nefza-Sejnane district (Tunisia): new insights into mineralization and mammalian biostratigraphy

The mining district of Nefza-Sejnane (Tunisia) encloses numerous ores and raw materialdeposits, all formed in relation with successive Fe-rich fluids of meteoric and/or hydrothermalorigins. Here, for the first time in Tunisia, (U-Th)/He ages were obtained on supergene goethite fromvarious localities/deposits of the district highlight direct dating of significant weathering episodesduring late Tortonian and late Pleistocene. These weathering events are most likely associated withfavorable conditions that combine (i) wet climate displaying sufficient meteoric water/fluid; and (ii)regional exhumation, due to large-scale vertical lithospheric movements enhancing the percolation offluids. Matched with previous works, these results refine the stratigraphic frame for the polymetallicmineralization and clay deposits in the district, confirming the influence of meteoric fluids circulationduring the late Cenozoic. As a consequence of the new (U-Th)/He data, we moreover propose ataxonomic and stratigraphic revision of the well-known mammalian fauna from the Fe-rich Douahrialocality, suggesting an early Tortonian age for the fossils, i.e., prior to the first episode of meteoricevent in the area.