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

The Neogene Guercif Basin of northeastern Morocco is the eastern continuation of the Rifean foredeep, from which it has been separated by the late Neogene uplift of the Tazzeka spur of the Middle Atlas. A dense grid (more than 1200 km) of seismic reflection profiles across the basin acquired during various surveys (1977, 1982, 1984-1985), the drilling of several wells, used to calibrate the seismic profiles, in particular those affecting the Neogene-Quaternary sequence, as well as the available superficial geological data, allow us to describe the late Tertiary-Quaternary evolution of this basin. The Guercif Basin is superimposed on late Cretaceous-Eocene inversion structures 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 Tortonian extension is observed, but by the end of the Tortonian an overall compressional 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 is also responsible for the renewed uplift of the Middle Atlas and the Masgout uplift to the north of the basin. (C) 2000 Elsevier Science Ltd. All rights reserved.