MAJOR FRACTURE-ZONES OF MOROCCO - THE SOUTH ATLAS AND THE TRANSALBORAN FAULT SYSTEMS

Within the fractural pattern of Morocco, 35-45-degrees and 70-90-degre es directions are predominant. Most of the faults originated already d uring the Upper Palaeozoic and were repeatedly reactivated, later on. Two of the large fracture systems are considered here. The South Atlas fault system (SAF) is composed of different faults with directions va rying between 45-90-degrees. They were not functionally connected to t he southern hinge of the High Atlas until its Miocene uplift. Today, i t seems to be inactive on the whole. Both the tectonic data and the fa cies distribution of Mesozoic strata contradict clearly the interpreta tion that the SAF is a huge wrench-fault or even the Mesozoic plate ma rgin of Africa. The SW striking Transalboran fault system (TAF) is sti ll active. It crosses Morocco from Melilla to Agadir, showing again si ngular faults which are unified to extended lineaments only in a few a reas. The intervals between the faults are bridged by linear arrangeme nts of earthquake hypocenters. Sinistral massflow within the deeper pa rts of the lithosphere seems to be compensated at the surface by movem ents along pre-existing faults. For the Moroccan segment of the TAF, a sinsitral displacement is testified at least since the Oligocene, whi le the northeastern segments from the Rif to Spain did not even origin ate until the Pliocene. This would mean that sinistral shear was trans mitted from Africa into the accreted Alboran and Iberia blocks after t he Miocene collision.