Dalila Zaghbib-Turki

Enregistrement des événements remarquables de la limite Crétacé-Tertiaire dans la coupe d'Ellès (Tunisie)

Abstract The review of the Cretaceous–Paleogene interval deposits of the Elles section based on a detailed sampling gives a good characterization of the K/T boundary and reconstitution of the geological events underlining this boundary. Thus, the discovery of a thin Ir-rich layer, with Ni and Cr-rich spinel and shocked quartz is a well preserved record of the known cosmic event that occurred at that time. This sudden event is also corroborated by the quantitative and qualitative organic components distribution along the K/T interval. Added to some other long-term events (e.g. climatic, eustatic), it generated a mass extinction, at the K/T boundary, of specialists among the Globotruncanids and Heterohelicids planktic foraminifera species. Following this biological crisis, the biotic turnover into the Danian is slow. The underlining of all the Cretaceous–Tertiary interval biozones attests that the Elles section is complete. If compared to the K/T stratotype and El Kef II sections, the Elles section is found to display a better exposure of the K/T interval and shows more expanded zones and subzones. Such characteristics promote the Elles section to be considered as a parastratotype.

Rôle des microbialites et des « micro-encroûtants » dans la lithification récifale : exemples du Jurassique supérieur de l'Atlas maghrébin (Maroc et Tunisie)

In the Upper Jurassic, reefs from the Maghrebian Atlas, inter- and intraskeletal cavities were infilled by microbialites associated with microencrusters: Bacinella irregularis, Tubiphytes obscurus, Lithocodium aggregatum and encrusting forams. Microbialitic activity was the main lithifying agent in the reef framework both in the Tethysian and Atlantic buildups of the Maghreb Atlas. They occupied about 20 % of the whole biomass volume in the Oxfordian reef, 40 % in the Kimmeridgian reef (High Atlas, Morocco) and 25 % in the Tithonian bioherm (Tunisia).

L'Ammonitico Rosso (formation Zaress) de la dorsale tunisienne

Abstract The Upper Jurassic biostratigraphy, so far limited to the J. Zaress, is extended to the ranges of the Tunisian Dorsale. The AR facies (Fm Zaress) begins as early as the Middle/Upper Callovian and ranges up into the Lower Kimmeridgian (Planula Zone). Above, the grey limestones and overlying beds (Ressas Fm) span the rest of the Kimmeridgian and the Tithonian. Compared to the north-south axis, the Ammonitico Rosso fades develops earlier in the Dorsale on starving shoals while AR of J. El Haouareb are slope deposits fed from the north-south axis heights, where Callovian and Oxfordian are reduced or absent.

Planktonic foraminiferal extinction pattern, evolution, turnover, and geochemical anomalies across the Cretaceous/Paleogene boundary (K/Pg) in Izeh (Zagros Basin, SW Iran)

In the Izeh section (Zagros Basin, SW Iran), about two third of the planktonic foraminiferal species, representing less than 20% of the individuals, present in the Maastrichtian polytaxic assemblages, became suddenly extinct at the K/Pg boundary. This mass species extinction testifies end-Cretaceous catastrophic bioevent. The Cretaceous species remain became apparently extinct gradually during the earliest Danian. In fact the unkeeled globotruncanids (Globotruncanella and Rugoglobigerina) as well as the small heterohelicids (Heterohelix and Pseudoguembelina) were also affected by extinction and they were reworked in the basal Danian. Except guembelitriids which persisted longer time. The sudden species extinctions were selective, eliminating geographically restricted large, complex, and deeper dwelling forms (i.e., globotruncanids and large heterohelicids). Contrary, few cosmopolitan small, simple surface-subsurface dwellers (i.e., guembelitriids among small heterohelicids and hedbergellids) crossed the K/Pg boundary and survived the catastrophic event. This selective bioevent is related to the end-Cretaceous bolide and produced ejecta impact inducing major environmental changes as decrease in temperature, collapse of nutriment, and flow breakdown in the water mass stratification. Our geochemical results (δ13C negative shift, δ 18O positive shift, and trace elements anomalies) are consistent with the cooling due to the collision winter triggering collapse of nutriment. Especially the δ 18O values across the upper Maastrichtian and the K-Pg transition in Izeh section although they are lower; they report similar fluctuations to those in El Kef section. Thus these lower values may be indicative of somewhat warmer water at the sea floor. Besides, like as elsewhere, in Izeh, this Cretaceous end catastrophic bioevent is followed by a delayed gradual recovery. Thus, immediately after the K/Pg boundary was created a nearly empty niche in which persisted few Cretaceous survivors with dwarf individuals. These survivors despite they suffered very stressful environmental conditions, they constituted the root stock of globigerinids from which the Cenozoic planktonic foraminiferal species evolved and developed carnivorous food diet.

Mass Extinction and Turnover Recorded at the Cretaceous–Palaeogene Boundary in the Izeh Section (Zagros Basin, Southwestern Iran)

A detailed study has been made of the uppermost Maastrichtian–lower Danian marls of the Gurpi Formation, which are exposed at the Izeh section (central part of the Zagros Basin, southwestern Iran), and which were deposited above the compensation depth. The study has yielded diverse and abundant planktonic foraminifera, whose distribution allows the Cretaceous–Palaeogene boundary to be placed at about 1.5 m from the base of the studied series. Within this series, all the characteristic planktonic foraminiferal biozones are recorded. In addition, the results allow a model of extinction and turnover to be established.

The Sub-thrust And Sub-salt Exploration Potential In Tunisia, New Exploration Challenges

Searching for new challenges and exploration strategies, new-old techniques used abusively in the Gulf of Mexico (sub-thrust and sub-salt exploration) are applied for the first time in Tunisia. Beginning with the Sub-thrust prospectivity: In Central Tunisia North-South Axis (NSA) and Kairouan areas, 2D seismic acquisition shows series of high-angle reverse and thrust faults running through NE-SW trend across the area forms the boundary between the uplifted Atlas Foothill s terrain to the northwest and the low lying Pelagian Basin to the southeast. Alternatively, in Kairouan area (in the sub-surface), four investigated wells show a number of drilled thrusted hanging-wall structures. Basin modeling analysis using Basin Mod 1D; 2D and Basin view as well as seismic interpretation prove the existence of a theoretical potential on the sub-thrust footwall of these faults to the southeast, where they could be sourced directly from the Pelagi an Basin. Seismic lines show Cretaceous and Tertiary sediments dipping away from these faults into the basin. Potential reservoirs are the Ypresian El Garia (nummulitic limestone facies) and the Campanian Abiod formations they could be reservoir targets for this play. However, 2D seismic surveys are very limited and are of poor quality at present, but some initial lead areas have been already defined For the Subsalt prospectivity: targets are very poor understood in the northern African domain (Algeria, Tunisia and Libya). Using basin modeling and seismic data, several salt-canopies like structures have been identified and several leads have been defined notably in the southern Gulf of Gabes and in Gulf of Tunis.