The Viséan of the eastern Jebilet: biostratigraphic refinements and chronology events

Abstract

The eastern Jebilet successions record major palaeogeographic and tectono-sedimentary changes during the Variscan orogeny, but the chronology of key events remains incompletely constrained because of the many allochthonous carbonate units and the strong deformation. Here, three autochthonous outcrops and six allochthonous units of the eastern Jebilet nappe were sampled for microfossils, with emphasis on Viséan foraminifers recovered from washed residues and thin sections. Forty-five out of 155 samples yielded diagnostic assemblages which allowed a more precise biostratigraphy. The base of the Kharrouba Formation is dated for the first time as at least middle Viséan Cf5, and the middle and upper parts are Asbian Cf6γ1-2. An Upper Devonian age for the pre-Viséan deposits of eastern Jebilet is indicated by reworked Famennian conodonts collected from the base of the Kharrouba Formation. Most allochthonous units contain upper Viséan foraminiferal associations. These new data provide improved chronological constraints on (i) the Viséan transgression in eastern Jebilet, (ii) the emplacement of the eastern Jebilet nappe, (iii) the provenance of the nappe units and (iiii) the regional correlations between the Meseta and adjacent domains. Our results confirm a marine connection with the Palaeotethys Ocean, suggesting the proximity of the Meseta to Gondwana.