Subsurface structure of a foreland basin from analysis of gravity and aeromagnetic data: Revealing the basement structure of Gharb Basin, NW Morocco

Abstract

Located in NW Morocco, Gharb Basin (GB) is a part of the foreland basin that was formed at the front of the Rif cordillera. It stands as a transition zone between the Maamora Plateau, to the South, and the Rif Belt, to the North. The first features of this basin began to appear in the Middle Miocene due to the compression caused by the convergence of Eurasia and Africa. The correlation of drilling data with gravity and aeromagnetic data, as well as the use of seismic data, has made it possible to reconstruct the architecture of this basin and to identify new structures responsible for the Neogene evolution of this region.

In this context, the analysis and interpretation of data extracted from this set of tools (drilling, gravity and aeromagnetic data) have allowed for the reconstruction of the subsurface geometry of this basin, to identify the lineaments traversing GB and to provide an overview of its tectonic framework. Some of these lineaments match previously mapped structures, whereas combination of seismic data for imaging existing structures and lineaments derived from gravimetry and aeromagnetism allowed to highlight new structures. The main identified structures include NW-SE oriented blind thrust fronts located beneath the nappe complex, associated with the advance of the Prerif Nappe towards the SW, as well as NE-SW oriented transpressive faults, interpreted as inherited faults from the Hercynian Orogeny and reactivated during the last Pliocene-Quaternary compressive phase. These structures formed NW-SE bulges and NE-SW oriented ridges that likely played a significant role in controlling sedimentation within this part of the foreland basin.

The results highlight the importance of combined geophysical methods for describing the macrostructure and architecture of GB, which is critical for hydrocarbon and water exploration.