The Neogene-Quaternary evolution of the Guercif Basin (Morocco) reconstructed from seismic line interpretation

The Neogene Guercif Basin of northeastern Morocco is the eastern continuati on of the Rifean foredeep, from which it has been separated by the late Neo gene uplift of the Tazzeka spur of the Middle Atlas. A dense grid (more tha n 1200 km) of seismic reflection profiles across the basin acquired during various surveys (1977, 1982, 1984-1985), the drilling of several wells, use d to calibrate the seismic profiles, in particular those affecting the Neog ene-Quaternary sequence, as well as the available superficial geological da ta, allow us to describe the late Tertiary-Quaternary evolution of this bas in. The Guercif Basin is superimposed on late Cretaceous-Eocene inversion struc tures involving Jurassic half-grabens which are the downplunge northeastern continuation of the Middle Atlas. Extensive pre-Tortonian erosion, mainly due to tectonic uplift, occurred prior to the main Neogene subsidence event , which was due to the emplacement of the Rifean nappes. Minor early Torton ian extension is observed, but by the end of the Tortonian an overall compr essional regime began which continued into the Plio-Quaternary and involves minor reactivation of the pre-existing inversion structures as well as the formation of narrow salt-cored anticlines. The same compressional regime i s also responsible for the renewed uplift of the Middle Atlas and the Masgo ut uplift to the north of the basin. (C) 2000 Elsevier Science Ltd. All rig hts reserved.