Investigation of Lateral Lithological Heterogeneities and Groundwater Salinity Using MRS and TEM Methods

Abstract

Transient Electromagnetic (TEM) and Magnetic Resonance Sounding (MRS) methods were applied jointly to investigate lithological variations in the Dead Sea coast of Israel. The subsurface in this area is heterogeneous and composed of intercalated sand and clay layers over a salt rock, which is partly karstified. Groundwater is very saline, with a chloride concentration of 100-225 g/l. TEM is known as an efficient tool for investigating electrically conductive targets like saline water, but it is sensitive to the salinity of groundwater, the clay content and the porosity of rocks. MRS, however, is sensitive primary to groundwater volume but also to lithological variations in the subsurface. MRS is much less sensitive to variations in groundwater salinity in comparison with TEM. We show that MRS enables us to resolve the fundamental uncertainty in TEM interpretation caused by the equivalence between groundwater resistivity and lithology. Combining TEM and MRS in Nahal Hever area we have identified lateral extensions of different lithological formations.