| Abstrakt: |
Through two case studies from the Serj and Fahs areas in north-central Tunisia, we have demonstrated the importance of biostratigraphy for hydrogeological research. Two sections of the Campanian–Maastrichtian interval, corresponding to the Abiod Formation, have been studied for their microfaunal assemblages and lithofacies variations. The Abiod Formation constitutes an interesting target aquifer, exploited in many regions of Tunisia. The biostratigraphic analysis of the Khanguet Zelga section (Serj region) has provided the following biozones: G. Elevata Zone, G. Ventricosa Zone, and A. Mayaroensis Zone in association with Ostracoda, indicating an outer platform environment. The biostratigraphic analysis of the Houita Bou Ragouba section (Fahs region) shows that the Abiod Formation is essentially composed of marls with thin carbonate intercalations. It is subdivided into the following biozones: G. Elevata Zone, G. Ventricosa Zone, G. Calcarata Zone, G. falsostuarti Zone, and G. Gansseri Zone, associated with Ostracoda, indicating a deep marine environment. The biostratigraphic study has allowed us to constrain the age of potential carbonate reservoirs and associated unconformities. The stratigraphic study highlighted that the Abiod Formation exposed in the Serj area is more interesting for hydrogeological investigation than in the Fahs area. These results are confirmed by water borehole data located near the above-mentioned sections. The lithological description and well logs corresponding to the Abiod Formation exposed in the Serj region indicate the predominance and the important thickness (25 m in average) of the limestone layers, which are characterized by low gamma ray values. The Abiod aquifer displays a relatively high flow rate of 5 l/s. In the Fahs area, the limestone reservoir layers are less developed and their thicknesses do not exceed 10 m. The flow rate is so low that the water borehole is converted into a piezometer. [ABSTRACT FROM AUTHOR] |
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