Enhancing subsurface geological imaging of Angad Basin (northeastern Morocco) through the integration of gravity and electrical data: new insights into the Jurassic deep aquifer for groundwater exploration and development

Abstract

SUMMARY Constraining the knowledge of deep aquifer structure in the Angad Basin (Northeastern Morocco) remains one of the major challenges for successful borehole drilling projects. This study demonstrates how integrating gravity and electrical data can enhance subsurface geological imaging and provide valuable insights into geological structures relevant to groundwater exploration. Various gravity enhancement techniques, including vertical gradient, horizontal gradient, upward continuation, logistic filter, tilt angle and Euler Deconvolution, have been applied to gravity data in the Angad Basin to identify gravity anomalies and tectonic discontinuities. The resulting gravity maps reveal two elongated depressions trending in the NE-SW direction: the Beni Drar depression in the north and the Oujda depression in the south. Both depressions are delineated by strong gravity gradients, indicating the presence of faults. Multiscale analysis of gravity lineaments highlighted sharper features and identified two principal orientations: N070°–085° and N040°–050°, with the latter being more predominant. Faults striking in the N120°–140° are less prominent. These fault systems play a crucial role in dividing the bedrock into distinct horst and graben structures, aligning with the regional tectonic phases observed in northeastern Morocco. The faults are generally sub-vertical, with estimated depth values ranging from 1000 to 2680 m for 42 per cent of the lineaments. Additionally, the reinterpretation of vertical electrical soundings using 2-D inversion methodology provides insight into subsurface resistivity variations. The 2-D resistivity sections generated from this process illustrate vertical and lateral variations in electrical resistivity over distances of up to 30 km and depths of up to 2 km, revealing the geological layers that form the aquifer. These resistivity sections confirm the presence of multiple faults that significantly influence the structural configuration of the study area, validating the geometry of the two depressions previously identified through gravity data. The 2-D gravity modelling further corroborates and reinforces the findings from the resistivity section inversion, demonstrating that the shape of the residual gravity anomaly curve closely aligns with the morphology of the Jurassic roof structure. The results of this study highlight the complementarity and effectiveness of these two geophysical methods in advancing our understanding of the deep geological structure of the Angad Basin, particularly within the Jurassic limestone, which serves as the region's primary deep aquifer. These findings provide valuable insights for future hydrogeological research in the area.