Quaternary Alluvial Aquifer Study Using Integrated Geophysical Approach in Zaghouan Plain (Northeastern Tunisia)

Abstract

The study area Zaghouan Plain (northeastern Tunisia) is unique for its strategic Quaternary aquifer, which is, in a great proportion, composed of sand lenses that vary in thicknesses and forms. Conducting an integrative approach based on regional mapping and local studies helped provide precise calibration to identify convenient areas for hydrogeological explorations, which are focused on heterogeneous alluvial and fluvio-deltaic aquifers. To enhance the location and the extension of low density related to sand lenses porous aquifers, a regional gravity analysis supported by focused seismic interpretation was performed. Thus, advanced analyses were conducted in the Zaghouan Plain through the implementation of a regional–residual separation, a radially averaged power spectrum and tilt/TDX filter density models. During the process, two major negative gravity anomalies, associated with developed lenses system between Zaghouan Mountain and Henchir Bouslim anticline, were revealed. The anomalies differed in direction from E–W to NW–SE. They also varied widthwise from 1000 to 3000 m and depthwise from 1500 to 2000 m. Hence, with the aim of highlighting the detailed geometry of sand lenses and locating the most interesting zone for future hydrogeological exploration and/or recharge process, 1D time-domain electromagnetic and 2D electrical resistivity tomography studies were conducted and various techniques were applied in a local area situated in the main negative gravity anomaly.