Contributions to Geophysics and Geodesy Special issue, 2012 Paleomagnetic and AMS study of mesozoic basins of the northern central High Atlas. Tectonic implications B. Moussaid, Hmidou El-Ouardi D´ epartement de G´ eologie, Facult´ e des Sciences, Universit´ e Moulay Ismail 1 A. Casas, T. Rom´ an, B. Oliva Dpto. de Geolog´ ıa 2 J. Villala´ ın, S. Torres Departamento de F´ ısica, Universidad de Burgos 3 R. Soto Instituto Geol´ogico y Minero de Espa˜ na 4 Abstract: In this work we present some results of paleomagnetism and AMS in two Jurassic-Cretaceous basins in the Moroccan High Atlas. The A¨ ıt Attab and Ouaouizaght basins are located in the northern border of the central High Atlas, that forms part of the alpine Atlasic belt. It is an intraplate belt (Michard, 1976; Mattauer et al. 1977), resulting from inver- sion of extensional and strike-slip basins (Laville, 1985; Fedan, 1988). Both basins are filled with terrigenous deposits, silts and sandstones, with less frequent marly marine limestones, Upper Jurassic to Lower Creataceous in age. About 430 samples were drilled in 42 sites (20 sites in A?t Attab and 22 in Ouaouizaght), with a minimum of 11 samples per site. The samples underwent analysis of AMS in the magnetic laboratory of the University of Zaragoza. Some sister samples were chosen for the thermo-magnetic study, in order to decipher the magnetic mineralogy. After that, the specimens were used for the paleomagnetic study in the paleomagnetic laboratory of the University of Burgos. The magnetic susceptibility (Km) shows generally high values in the red facies and low values in the yellowish marly limestones. The shape param- eter T of the magnetic susceptibility ellipsoid shows positive values in most sites, reflecting an oblate magnetic fabric. The thermo-magnetic curve for red facies shows a sharp drop in magnetic susceptibility in the vicinity of 680 1 B.P. 11201 Zitoune Mekn´ es Maroc, bnmous@hotmail.fr, hmidouelouardi@yahoo.fr 2 Facultad de Ciencias, Universidad de Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza, Spain, acasas@unizar.es 3 Avda Cantabria s/n, 09006 Burgos, Spain, villa@ubu.es 4 C/Manuel Lasala, Zaragoza, Spain 86