Regional gravity analysis of the crustal structure of Tunisia |
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| Institution: | 1. Géoazur, Université Côte d''Azur, CNRS, IRD, Observatoire de la Côte d''Azur, UMR 7329, 250, rue Albert-Einstein, 06560 Sophia Antipolis, France;2. Czech Geological Survey, Centre for Lithospheric Research, Klárov 3, 118 21 Prague 1, Czech Republic;3. Institut des Sciences de la Terre d''Orléans, Université d''Orléans, CNRS, UMR7327, INSU, Bureau de Recherches Géologiques et Minières, Campus Géosciences 1A, rue de la Férollerie, 45071 Orléans cedex 2, France;4. Géosciences Montpellier, UMR 5243, Université Montpellier 2, CC 060, place Eugène Bataillon, 34095 Montpellier cedex 5, France;5. Département de Géologie, Université Abdelmalek Esaadi, 93003 Tetouan, Morocco |
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| Abstract: | Gravity data were integrated with seismic refraction/reflection data, well data and geological investigations to determine a general crustal structure of Tunisia. The gravity data analysis included the construction of a complete Bouguer gravity anomaly map, residual gravity anomaly maps, horizontal gravity gradient maps and a 2.5-D gravity model. Residual gravity anomaly maps illustrate crustal anomalies associated with various structural domains within Tunisia including the Sahel Block, Saharian Flexure, Erg Oriental Basin, Algerian Anticlinorium, Gafsa Trough, Tunisian Trough, Kasserine Platform and the Tell Mountains. Gravity anomalies associated with these features are interpreted to be caused either by thickening or thinning of Palæozoic and younger sediments or by crustal thinning. Analysis of the residual gravity anomaly and horizontal gravity gradient maps also determined a number of anomalies that may be associated with previously unknown structures. A north-south trending gravity model in general indicated similar subsurface bodies as a coincident seismic model. However, thinner Mesozoic sediments within the Tunisian Trough, thinner Palæozoic sediments in the Gafsa Trough, and a greater offset on the Saharian Flexure were required by the gravity data. Additionally, basement uplifts under the Kasserine Platform and Gafsa Trough, not imaged by seismic data, were required by the gravity data. The gravity model revealed two previously unknown basins north and south of the Algerian Anticlinorium (5 km), while the Erg Oriental Basin is composed of at least two sub-basins, each with a depth of 5 km. |
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