Revised fusulinid biostratigraphy of the Middle–Late Permian of Jebel Tebaga (Tunisia)

Abstract

Most carbonate series of Jebel Tebaga (Tunisia) are assigned to the Capitanian (last stage of the Middle Permian); however, their accurate correlation with the El Capitan stratotype in the USA and with contemporaneous Tethyan localities remains unclear. With the intent to establish more accurate lithostratigraphic and biostratigraphical divisions, (1) we re-sampled bed-by-bed the classical field sections of Jebel Tebaga; (2) we revised the lithostratigraphical units E-I to E-VI, and (3) we selected 9 fusulinids in order to characterize more precisely local bioevents. We have therefore studied 3 giant genera (Chusenella, Neoschwagerina and Yabeina), 3 medium-sized taxa (Dunbarula, Rauserella and Yangchienia), and 3 small size genera (Lantschichites, Codonofusiella and Reichelina). The first group was known to synchronously disappear at the time of the end-Guadalupian mass extinction. The thirth group was generally considered to be characteristic of the early Late Permian, after a Lilliput effect among the fusulinid groups, during which the dwarfs replaced the giants. Our data show that, in Jebel Tebaga, the so-called Wuchiapingian small forms Codonofusiella and Reichelina appear very early in the Late Capitanian. In some hills of the Tebaga area (i.e., Baten Beni Zid and Jebel Seikra), Codonofusiella and Reichelina even dominated the fusulinid assemblages during two short episodes. The first episode is located near the base of the Capitanian series; the second one, although located near its top, remains Capitanian in age, because it took place before the local disappearance of the three giants Neoschwagerina, Yabeina and Chusenella. As the sequence becomes sandier after this bioevent, the boundary with the Wuchiapingian (first stage of the Late Permian or Lopingian) cannot be well positioned. The end-Guadalupian event is only marked by this sedimentological modification. Because the Late Permian Cheguimi sandstone is entirely devoid of foraminifers and conodonts, no local subdivisions can be proposed in this series.