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Majed Jabbour, University of Pau (France)
Damien Dhont, University of Pau (France)
Yves Hervouet, University of Pau (France)
Emmanuel Pajot, University of Pau (France)
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In areas of important relief declivity, the lack of seismic and borehole data is a certain limitation for imaging the deep structure of folds. However, the deep geometry of anticlines can be deduced from their surface parameters, which are well displayed on remote sensing data. In southern-central Tunisia, analysis of Landsat 5 and 7 images provides an updated geological mapping of large (40 km x 10 km) E-W-trending anticlines exposed in the Metlaoui chain. We used the fault-propagation fold model to define the geometry of the anticlines and related structural traps. Surface data (fold wavelength, fold amplitude, local dips) were derived both from the combination of the updated geological map and a digital elevation model and from field observations. These data were used to determine the geometric parameters of folding in its present-day shape and structure (ramp angle, ramp height, thickness changes in the backlimb, shortening rate) allowing to identify the depth of the décollement level in order to reconstruct the deep structure of the anticlines. From a numerical modelling, we show that the décollement level associated to the formation of the Metlaoui anticlines is located in the salt term of the Nara formation (Jurassic), at 5 km depth below the top of the Abiod formation (Maastrichtian). Folding is compatible with a mean shortening of 1.25 km since initiation of folding.
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