Sequence stratigraphy and micropaleontology of the Triassic series from the southern part of Tunisia

Abstract

The Triassic series in the southern part of Tunisia, only known from the oil exploration wells in the Kirchaou area (sandy series from Early Scythian to Ladinian) and in its Djeffara/Dahar-North outcrops (alternating series from Ladinian to Rhaetian) is now subdivided into 10 Depositional Sequences (DS) sensu Vail et al. (1987), T₁ to T₁₀ corresponding approximately to most of the 3^rd order eustatic cycle from the Haq et al. curve (1987). Within the DS succession, 3 basal discontinuities (or sequence boundaries) appear to be important in Tunisia: the base of T₂, correlated to the “H Discordanz” from the “Germanic Triassic” (intrascythian); the base of T₆ (intracarnian), well-marked by the Sidi Stout angular discordance from Dahar North; the base of T₈ (intranoirian additional DS, previously recognized in Germany) pointed by the cartographic discordance of Low Stand conglomerates. The shallow-water facies from the carbonate Transgressive Systems Tracts of 7 Tunisian DS contain macrofauna, such as Myophoria, and particularly 6 successive benthonic Foraminifera assemblages, F₁ to F₆ giving chronostratigraphic informations as complement of Palynomorphs and Conodonts. Belonging to the genus Meandrospira, Triadodiscus, Aulotortus, Lamelliconus, Endothyranella, Pilamminella, Agathammina, Gandinella etc.…, most of them, commonly used as zone-indices in Europe, are new in Tunisia.