Abstract
Electric resistivity sounding and tomography, as well as electromagnetic sounding, are the classical methods frequently used for hydrogeological studies. In this work, we propose the development and implementation of an original integrated approach using the unconventional hydro–geophysical methods of gravity and seismic reflection for the fast, large–scale characterization of hydrogeological potential using the Ain El Beidha plain (central Tunisia) as an analogue. Extending the values of vintage petroleum seismic reflection profiles and gravity data, in conjunction with available geological and hydrogeological information, we performed an advanced analysis to characterize the geometry of deep tertiary (Oligocene and Eocene) aquifers in this arid area. Residual and tilt angle gravity maps revealed that most gravity anomalies have a short wavelength. The study area was mainly composed of three major areas: the Oued Ben Zitoun and Ain El Beidha basins, which are both related to negative gravity trends corresponding to low–density subsiding depocenters. These basins are separated by an important NE–SW trend called “El Gonna–J. El Mguataa–Kroumet Zemla” gravity high. Evaluation of the superposition of detected lineaments and Euler deconvolution solutions’ maps showed several NE–SW and N–S relay system faults. The 3D density inversion model using a lateral and vertical cutting plane suggested the presence of two different tectonic styles (thin VS thick). Results from the gravity analysis were in concordance with the seismic analysis. The deep Oligocene and Eocene seismic horizons were calibrated to the hydraulic wells and surrounding outcrops. Oligocene and Eocene geological reservoirs appear very fractured and compartmented. The faulting network also plays an important role in enhancing groundwater recharge process of the Oligocene and Eocene aquifers. Finally, generated isochron maps provided an excellent opportunity to develop future comprehensive exploration surveys over smaller and more favorable areas’ sub–basins.
Highlights
In arid and semi–arid regions, surface water resources are limited
Geological outcrops surrounding the Ain El Beidha plain are characterized by the presence of Triassic to Miocene deposits (Figure 1) [7,8,11,17,23]
The Miocene, Oligocene, and Eocene deposits can be recognized in the western side of the N–S axis (Figure 2)
Summary
In arid and semi–arid regions, surface water resources are limited. These areas present a growing need for potable and irrigation water, and the population is obliged to use groundwater. These studies were performed to detail the tectonic settings and characterize the subsurface, water–bearing formations of the Al Jaww plain, one of the most important groundwater reserves of the United. This work aims to use regional gravity and seismic reflection data, complemented by geological/hydrogeological background information, to detail the deep tectonic settings of Oligocene and Eocene groundwater reservoirs. During the last few decades, The Ain El Beidha plain has changed due to a fast and dynamic evolution in human and agricultural activities, leading to an increase in the demand for potable and irrigation water In this arid area, Oligocene siliciclastic and Eocene carbonate layers are the most interesting and strategic deep aquifers [19,21,22]. Groundwater flow direction. (Adopted from [19]). (18) Position of the picture. (C) General view of the Ain El Beidha plain
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