## 4 Results and Discussion
### Time-Domain Electromagnetic
Figure 5 shows the fit between the induced voltage curves measured in the field (dots) and those generated (curves) by the resistivity model (thick red line). The figure also shows the apparent resistivity obtained as a function of time in the first and last of these stations (S-1 and S-10). For each of these curves, the fit between the field and the model (by the ZONDTEM1D software) lines is observed. The curves observed in the field at station S1 and the modeled ones (Figure 2) are represented and compared when we use a central-loop device ('Center 1' in Figure 5A) and a single-loop device ('C_3' in Figure 5B). First, the good fit of the curves stands out in both cases, with a root mean square (RMS) error of 2.7% and 3.3%, respectively. After the data inversion in both cases, similar results in the resistivity/depth curves are observed. In both cases, at shallow depths, there is an increase in resistivity values that correlates with the Jurassic dolomite aquifer, unit that outcrop in nearby sectors (Figure 2). Under this unit, a set of more conductive facies appears that would correspond to the Triassic clays. Within the Triassic unit, generally in the upper part, the increase in resistivity can be associated with the increase in evaporitic layers (Figure 5A,B). Below 400 m, the sharp increase in resistivity is associated with phyllites of the Paleozoic basement. This interpretation is corroborated by the information of the thicknesses observed in the nearby outcrops (Figure 2B) and to the information provided by the seismic profile in Figure 3A. Therefore, TDEM curves could determine the thickness of a geological unit accurately. However, TDEM curves do not allow to establish the correct resistivity value for each level, as other authors have already pointed out. In this study, Figure 5 represents resistivity values after inversion; their abrupt increases or decreases allow deducing the presence of different lithologies. Nevertheless, the modeled resistivity values do not correspond to the real resistivity of the proposed lithologies. It should be noticed that the shape of the curve, with changes in the tendency of increase or decrease in resistivity, allows detecting lithological changes. However, absolute values should not be taken into account: the dolomites offer average resistivity values in the 200-400 \(\Omega\)m range (Figure 5), that can be lower than 100 \(\Omega\)m in some stations (S1, S8, S9, and S10) and greater than 10\({}^{5}\)\(\Omega\)m in others (S4). On the other hand, despite the overall similarity in the models of Figure 5A,B, a significant difference must be highlighted: the slope change of the decay curve of the induced potential. In the case of the central-loop device, the slope of the curve is lower, reaching depths of approximately 600 m with induced potential data on the order of 10 \(\mu\)V. With much lower voltage values, the curve continues to show a highly stable trend. However, using the single-loop device, the slope of the potential decay  
Figure 5: Induced voltage curves (blue line) and apparent resistivity (red line) as a function of time. For each of them, the fit between the field and the model (by the ZONDTEM1D software) lines is indicated. The interpretation after the inversion of the data is also included; red straight lines represent the resistivity as a function of the depth. In charts A and B, data collected at station S1 (see Figure 2) using two different devices are represented: central-loop (**A**) and single-loop (**B**). In charts (**C**,**D**), data collected at station S10 (see Figure 2) using central-loop (**C**) and single-loop (**D**) devices are also shown. curve is greater. Thus, from approximately 150 m depth, the induced voltage values would be less than 10 \(\upmu\)V.  
The same comparison is performed at station S10 (see its location in Figure 2). Again, the good fit of the curves stands out, having an RMS error of 0.6% with a central loop ('qcenter_8' in Figure 5C) and 1.6% with a single loop ('q_2' in Figure 5D).