Structural control on a Ypresian karstic aquifer revealed by an integrated geophysical and geological approach: the Mateur imbricated thrust zone (northern Tunisia)

Abstract

We present a characterization of a poorly studied karstic aquifer, documenting the geometry, resistivity properties and the control of structural discontinuities that affect the Ypresian limestone cropping out in the Mateur imbricated thrust zone in northern Tunisia. The karst system was produced by meteoric diagenesis. Geophysical methods and field investigations were useful in extracting geological features. First, our findings suggest that N110–N140 directions are the preferred dissolution paths orientated parallel to strike-slip and extensional faults. Second, the gravity data analysis (regional–residual separation, horizontal gravity gradient and Euler deconvolution) show a particular tectonic node as a junction of the NE–SW and NW–SE directions. Third, 2D electrical resistivity models display various karstification typologies with high (&gt;1000 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>Ω</mml:mi> </mml:math> m), medium (between 200 and 1000 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>Ω</mml:mi> </mml:math> m) and low (&lt;100 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>Ω</mml:mi> </mml:math> m) electrical resistivity zones. These electrical resistivity models have contributed to the establishment of a conceptual structural model of the global karst features. Finally, 2D electrical resistivity tomography (ERT) and 1D time-domain electromagnetic analysis highlighted the presence of potential water zones integrated into the aquifer. Thematic collection: This article is part of the Karst: Characterization, Hazards &amp; Hydrogeology collection available at: https://www.lyellcollection.org/topic/collections/karst