CRUSTAL CONFIGURATION OF THE NAAMA AND EL BAYADH REGION OF NORTHWEST ALGERIA: INFERENCES FROM A GRAVITY AND MAGNETIC ANALYSIS

Northwestern Algeria is located in a region where the Saharan Atlas borders the Saharan Platform along the South Atlas Front. The origin of the South Atlas Front is controversial, thus a detailed gravity and magnetic analysis constrained by seismic reflection profiles and well data was conducted to determine the structural configuration of this region. A residual gravity anomaly map created using upward continuation and a reduced to the pole magnetic anomaly map indicated a series of northwest-trending maxima anomalies parallel to the Atlassic orogeny folds and faults within the Saharan Atlas and east-trending maxima within the Benoud foreland basin. These maxima mostly coincide with basement uplifts based on seismic reflection profiles. Depth analyses based on upward continuation, two-dimensional forward modeling and 3D inversion models of the gravity and magnetic data indicated that the source of the maxima are mainly 5 km in depth with the magnetic sources being deeper than the gravity sources. The gravity and magnetic models indicate that the source bodies are steep-sided and coincide with interpreted faults from the seismic reflection profiles. The maxima anomalies are interpreted to mainly be caused by basement uplifts instead of variations in density and/or magnetic susceptibility in the Paleozoic or older basement lithologies. The analysis of the gravity and magnetic data suggests that the South Atlas Front in western Algeria was formed by a mixture of thin- and thick-skinned tectonics.