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The lower and middle Berriasian in Central Tunisia: Integrated ammonite and calpionellid biostratigraphy of the Sidi Kralif Formation

Maalaoui K., Zargouni F.

Acta Geologica Polonica

2016

Vol. 66, no. 1

43--58

The lower and middle Berriasian sedimentary succession of the Sidi Kralif Formation has been a subject of biostratigraphic study in two key sections in Central Tunisia. Our contribution is an attempt to better define the basal Berriasian interval, between the Berriasella jacobi Zone and the Subthurmannia occitanica Zone. Zonal schemes are established using ammonites and calpionellids, and these permit correlation with other regions of Mediterranean Tethys and beyond. The use of biomarkers afforded by microfossil groups has allowed characterization and direct correlation with four widely accepted calpionellid sub-zones, namely Calpionella alpina, Remaniella, Calpionella elliptica and Tintinopsella longa. The two ammonite zones of Berriasella jacobi and of Subthurmannia occitanica are recognised on the basis of their index species. The parallel ammonite and calpionellid zonations are useful as a tool for correlation and calibration in time and space, thus allowing a better definition of a J/K boundary. The presence of four Berriasian calpionellid bioevents is recognised: (1) the ‘explosion’ of Calpionella alpina, (2) the first occurrence of Remaniella, (3) the first occurrence of Calpionella elliptica and (4) the first occurrence of Tintinopsella longa. The last is here documented as coeval with the presence of Subthurmannia occitanica, which marks the lower/middle Berriasian boundary.

Malm-Berriasian formations of northern Tunisia: updated biostratigraphy, regional correlations and western Tethys geodynamic context

Boughdiri M., Sallouhi H., Cordey F., Maalaoui K., Soussi M.

Volumina Jurassica

2006

Vol. 4, no. 1

148-149

Upper Jurassic – lowermost Cretaceous formations in northern Tunisia include the Zaress Fm. of the Tunisian “Dorsale” (Ammonitico Rosso facies: Middle Callovian-Oxfordian) and the corresponding beds from Fahs and Jédidi fms (radiolarian-bearing series: Upper Bajocian-Oxfordian) of the nearby surrounding exposures and the “Tunisian Trough”, respectively. These heteropic facies are overlain by the marl/limestone alternations of the Beni Kleb Fm. (Kimmeridgian – Middle Berriasian). Recent integrated biostratigraphic investigations (ammonites, radiolarians, calpionellids) undertaken in different palaeogeographical domains of northern Tunisia allowed a precise dating of the Malm -Berriasian fms. Revised lithostratigraphy and regional correlations lead to the recognition of an updated facies repartition in central and northern Tunisia. Within the North Maghrebian Range, main palaeogeographical segments can be outlined considering facies affinities: the North-South Axis successions of Central Tunisia show close affinities with those described from the Middle and Central AurŻs Range (eastern Algeria). The Tunisian “Dorsale” series are to be compared with corresponding beds of northern AurŻs, Hodna Mounts and the South Tellian Border (Tiaret area), in Algeria, and with the Prérif and Mésorif Upper Jurassic facies, in Morocco. Deeper facies of the Tunisian Dorsale surrounding outcrops and the “Tunisian Trough” are closer to successions described in ancient literature from the Babors and the West Numidian Range of Algeria. All these equivalent successions from the external segments of the Maghrebian Range are quite distinctive from the Internal Rif and Kabylias “Dorsales calcaires” series. Both facies types have evolved in clearly different palaeogeographical realms related with the tectonic evolution of north- and south-western Tethys margins since the Triassic – Early Jurassic times.