In this paper, we present the first palaeomagnetic data (51 sites) for Mesozoic (Lower–Middle Jurassic) sediments of the Moroccan Central High Atlas and address the study of a widespread remagnetization. The remagnetization is characterized by a very stable component with systematic normal polarity, carried by magnetite. The relationship between the magnetic properties and location within the basin suggests that the acquisition of the remagnetization is controlled by basin geometry. Fold-tests indicate that the overprint acquisition is syn-folding in some structures but clearly predates the Tertiary compressional stage. Using the small circle intersection method we have calculated the remagnetization direction ( D = 336.4°, I = 29.2°). Comparison with the global apparent polar wander path indicates that the remagnetization was acquired during the Late Cretaceous (probably Cenomanian). Considering both the basinal confinement of remagnetization and the connection with other remagnetization events in the western Tethys, we propose a scenario explaining widespread remagnetizations in the region, concerning both basin-scale conditions mainly related to sediment thickness and a regional-scale thermal event acting as catalyst of remagnetizations in those sedimentary basins that satisfy the basin-scale conditions.

Palaeomagnetic data, and specifically remagnetizations, are used to constrain the geometric reconstruction at 100 Ma of three anticlines cored by gabbroic intrusions and Triassic shales in the Central High Atlas, Morocco. Previous palaeomagnetic results have revealed that the Mesozoic sediments of this region acquired a pervasive remagnetization at the end of the Early Cretaceous. The restoration of palaeomagnetic vectors to the remagnetization stage (100 Ma) allows us to determine the dip of the beds during this period and, thereby, to reconstruct structures during that time and determine the relative contributions of Mesozoic magmatic/diapiric uplift vs. Cenozoic compression to the present‐day dip. Our results indicate that three major anticlines in the Central High Atlas (Tasraft, Tassent and Tissila) were initiated to different degrees before the Late Cretaceous and were reactivated during Cenozoic compression to acquire their present‐day geometry. We also discuss the origin of these structures.

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Origin of lateral variations of the Ypresian deposits in the dome zone in northern Tunisia. In the Mejez El Bab-Testour area (northern Tunisia), the Early Eocene extension induced block tilting and salt tectonics of the Triassic evaporites. Tectonic events and halokinesis have determined the organization of Ypresian sediments. Diapiric structures have been generated during Cretaceous along the east-west, north-south and NE-SW major faults and emphasised during Lower Eocene. In this region, the Ypresian deposits constitute a filling sequence and show several thickness and facies variations. They correspond to a Nummulitic and Globigerina mixed facies characterizing a platform-basin transition zone. To cite this article: H. El Ouardi, C. R. Geoscience 334 (2002) 141-146.  2002 Académie des sciences / Éditions scientifiques et médicales Elsevier SAS Tunisia / dome zone / Ypresian / mixed facies / halokinesis / blocks tilted / tectonic inversion Résumé -Dans la région de Mejez El Bab-Testour, en Tunisie septentrionale, la distension de l'Éocène inférieur détermine un système de blocs basculés et provoque des mouvements halocinétiques des évaporites triasiques. La tectonique cassante et l'halocinèse ont déterminé l'organisation des dépôts yprésiens. Les structures diapiriques générées pendant le Crétacé, le long de failles majeures nord-sud, est-ouest et NE-SW, se sont accentuées durant l'Éocène inférieur. Dans cette région, les dépôts yprésiens constituent une séquence de comblement et montrent de nombreuses variations d'épaisseur et de faciès. Ils correspondent à un faciès mixte à Globigérines et Nummulites, caractéristique d'une zone de transition plate-forme-bassin.

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