Figure 1 - available via license: Creative Commons Attribution 4.0 International
Content may be subject to copyright.
Source publication
The Tartar aquifer unit, is located at the SSO of the city of Boujdour, at a distance of nearly 86 km, and crossed (in its western part) by the National Road N1 connecting the towns of Boujdour and Lagouira passing through the vicinity of the city of Dakhla (PK40). It is exploited by rural settlements for domestic use (especially the inhabitants of...
Contexts in source publication
Context 1
... topography of the study area is monotonous and is summarized in a series of plateaus slightly inclined towards the Atlantic Ocean (Figure 1) except for the presence of the dune cordon oriented SSO-NNE sometimes separated by slope breaks and by small discontinuous rock cuestas. ...
Context 2
... situation of the electrical soundings drilled in the study area, wedging boreholes, the two named groundwater wells (Khtout Hobia and Khtout Trayh) of interest to this area and also the geo-electric sections are shown in the following Figure 10. ...
Context 3
... for conductor C1, surmounted by this alternation, it corresponds to the clay and silty formations with the presence of flint belonging to the median Eocene starting point. This conductor C1, well-marked on the diagram, is well developed and reaches a thickness of 250 m in line with the 20TJ23 standard borehole diagram plumbing oil drilling 43-1 ( Figure 11) with a line length AB = 10,000 m. This conductor surmounts the R2 + R3 resistant assembly responsible for the final ascent of the curve whose roof reaches a depth of 910 m coinciding, in its highest part with the carbonate formations of the Eocene base and the silty one with the presence of Paleocene flint. ...
Context 4
... conductor surmounts the R2 + R3 resistant assembly responsible for the final ascent of the curve whose roof reaches a depth of 910 m coinciding, in its highest part with the carbonate formations of the Eocene base and the silty one with the presence of Paleocene flint. In its basal part, it is attributed to sandy-sandstone formations with upper Cretaceous clay inter-leavings and dolomitic levels and sandy-sandstone formations with lower Cretaceous conglomeratic levels interleaved (Figure 11). ...
Context 5
... correlation between the different electrical soundings made it possible to differentiate between two families of electrical soundings A and B (Figure 12), each characterized by a well-defined electrical response. The difference between these two families lies in the geoelectric behaviour of the resistant level R and its sandy-sandstone covering. ...
Context 6
... A surface resistant assembly R0 with a thickness of about 5 m which would correspond to the lumachellic limestone slab with siliceous sandstones at the base; Examination of the diagram of the 13TA6 electrical sounding (Figure 13) shows the presence, in its lower part from the resistor R, of the same succession of resistive and conductive layers R, Dt1, Dt2 and C1 as that of the previous 9TA6 diagram (Figure 13). However, in particular, there is a lateral change of facies within the overlap of the resistant level R, especially the layer above it where the intermediate level Ao highlighted by the previous diagram has manifested itself electrically as a conductor and is none other than the C0 conductor with a resistivity of 18 ohm•m. ...
Context 7
... A surface resistant assembly R0 with a thickness of about 5 m which would correspond to the lumachellic limestone slab with siliceous sandstones at the base; Examination of the diagram of the 13TA6 electrical sounding (Figure 13) shows the presence, in its lower part from the resistor R, of the same succession of resistive and conductive layers R, Dt1, Dt2 and C1 as that of the previous 9TA6 diagram (Figure 13). However, in particular, there is a lateral change of facies within the overlap of the resistant level R, especially the layer above it where the intermediate level Ao highlighted by the previous diagram has manifested itself electrically as a conductor and is none other than the C0 conductor with a resistivity of 18 ohm•m. ...
Context 8
... in particular, there is a lateral change of facies within the overlap of the resistant level R, especially the layer above it where the intermediate level Ao highlighted by the previous diagram has manifested itself electrically as a conductor and is none other than the C0 conductor with a resistivity of 18 ohm•m. The presence of marl past and fine sands instead of coarse ones at the Holocene base could contribute to a decrease in resistivity from 55 ohm•m (level A0 -SEV 9TA6, Figure 13) to 18 ohm•m (level C0-SEV 13TA6, Figure 13) in this case. ...
Context 9
... in particular, there is a lateral change of facies within the overlap of the resistant level R, especially the layer above it where the intermediate level Ao highlighted by the previous diagram has manifested itself electrically as a conductor and is none other than the C0 conductor with a resistivity of 18 ohm•m. The presence of marl past and fine sands instead of coarse ones at the Holocene base could contribute to a decrease in resistivity from 55 ohm•m (level A0 -SEV 9TA6, Figure 13) to 18 ohm•m (level C0-SEV 13TA6, Figure 13) in this case. ...
Context 10
... the case of the 3TA4 electric borehole diagram (Figure 14) adjacent to Khtout Hobia wells, the conductor C0 overlying the resistance level R has a resistivity value of 55 ohm•m close to that obtained from the intermediate level A0 in way of the 9TA6 electric borehole diagram (Figure 14). ...
Context 11
... the case of the 3TA4 electric borehole diagram (Figure 14) adjacent to Khtout Hobia wells, the conductor C0 overlying the resistance level R has a resistivity value of 55 ohm•m close to that obtained from the intermediate level A0 in way of the 9TA6 electric borehole diagram (Figure 14). ...
Context 12
... Increasingly high grade from south to north; The plunging of the roof and wall of the resistance fighter with an increasingly important development of its roofing. This dive is illustrated in Figure 14. ...
Context 13
... Electrical sounding 6TA5 (Figure 15) Following the preliminary interpretation of the electrical holes made just at the end of the acquisition of the field measurements, it was possible to choose the reconnaissance drill site 265/124 directly above the 6TA5 electrical hole, belonging to family A of the electrical holes, where its diagram (Figure 15) shows the same sequence of electrical layers as the 9TA6 electrical hole diagram ( Figure 13). This electrical borehole is located in a high zone where the roof and wall of the resistant R, admitted aquifer, are located respectively 15 and 37 m deep. ...
Context 14
... Electrical sounding 6TA5 (Figure 15) Following the preliminary interpretation of the electrical holes made just at the end of the acquisition of the field measurements, it was possible to choose the reconnaissance drill site 265/124 directly above the 6TA5 electrical hole, belonging to family A of the electrical holes, where its diagram (Figure 15) shows the same sequence of electrical layers as the 9TA6 electrical hole diagram ( Figure 13). This electrical borehole is located in a high zone where the roof and wall of the resistant R, admitted aquifer, are located respectively 15 and 37 m deep. ...
Context 15
... Electrical sounding 6TA5 (Figure 15) Following the preliminary interpretation of the electrical holes made just at the end of the acquisition of the field measurements, it was possible to choose the reconnaissance drill site 265/124 directly above the 6TA5 electrical hole, belonging to family A of the electrical holes, where its diagram (Figure 15) shows the same sequence of electrical layers as the 9TA6 electrical hole diagram ( Figure 13). This electrical borehole is located in a high zone where the roof and wall of the resistant R, admitted aquifer, are located respectively 15 and 37 m deep. ...
Context 16
... Electrical sounding 3TA6 (Figure 16 In this case of the diagram, we are witnessing, in particular, a deepening of the roof and wall of the resistant level R which reach depths of 32 and 84 m respectively with a thickening of the resistant R and its covering where the thickness of resistant R reaches 52 m instead of 34 to 35 m at the level of the electrical soundings 9TA6 (Khtout Trayh) and 13TA6. As for its resistivity reached, in this case, of 278 ohm•m, it remains comparable to that obtained from the 3TA4 electric borehole of 262 ohm•m. ...
Context 17
... resistant R would correspond, in its highest part, to the sandstones and lumachelles of the Moghrebian-Pleistocene (Marine Pliocene) age and to the lumachellique sandstones and limestones of the Miocene age (Ugranat Formation) of the Neogene roof. In contrast, outside the heavily subsided areas, at the level of the area characterized by the presence of family A of electric boreholes, as in the case of the diagrams of electric boreholes 13TA6, 9TA6 ( Figure 13) and 3TA4 (Figure 14) where the sandstone formations of the Moghreb-Pleistocene surmount the sandy marls of the Miocene roof (intermediate level Dt1). ...
Context 18
... resistant R would correspond, in its highest part, to the sandstones and lumachelles of the Moghrebian-Pleistocene (Marine Pliocene) age and to the lumachellique sandstones and limestones of the Miocene age (Ugranat Formation) of the Neogene roof. In contrast, outside the heavily subsided areas, at the level of the area characterized by the presence of family A of electric boreholes, as in the case of the diagrams of electric boreholes 13TA6, 9TA6 ( Figure 13) and 3TA4 (Figure 14) where the sandstone formations of the Moghreb-Pleistocene surmount the sandy marls of the Miocene roof (intermediate level Dt1). ...
Context 19
... diagrams of the 5TA7 and 7TA3 electrical boreholes ( Figure 17) were chosen to highlight the lateral change in the facies of the top part of the resistant level R of family A of the electrical boreholes. This resistor R manifested itself electrically, in this case of diagram, sometimes in a downward bilayer Bc0 (electric borehole 5TA7) and sometimes in an intermediate level descending Dt0 (electric borehole 7TA3). ...
Context 20
... 400 m (Figures 18-20) They are based on the gross apparent resistivity values (ρa) recorded at each electrical borehole measuring station for line lengths AB = 200 m, AB = 300 and AB = 400 m. They have a qualitative aspect taking into account the factors that influence these measurements such as the variation in altitude between electrical boreholes, the resistivities of surface soils and the lateral variations in facies. ...
Context 21
... have a qualitative aspect taking into account the factors that influence these measurements such as the variation in altitude between electrical boreholes, the resistivities of surface soils and the lateral variations in facies. The 03 maps (Figures 18-20) reflect the electrical behaviour of the resistant level R and, in places, that of the underlying intermediate level Dt1, whose roof would sometimes correspond to sandy-gravel formations, especially in subsided areas, and sometimes to sandy marls outside these subsidised areas. ...
Citations
The resistivity technique involving Vertical Electrical Sounding (VES) was carried out North of Ain Al Atti area, in Zaouia Jdida locality, with the aim of delineating zones not contaminated by the extension of the salinity and determining the potentiality of the existing aquifers. The measurements of apparent resistivity were collected using Molisana Apparecchiature Elettroniche (MAE) advanced geophysics instruments and were taken in twenty two VES points, along four profiles oriented N-S. The VES profiles were implanted using the Schlumberger configuration. VES Interpretation results shows that the potential aquifer horizon consists of the infracenomanian sand. The isopach map shows that the thickness of this geological formation varies between 20 m and 170 m. The sand layer is more thick (>80 m) along the profiles P3 and P4, with a maximum of about 170 m at 2P4 and 3P4 VES points. The isohypse map indicates that the sand formation is shallow (<10 m) in the East, and the depth of the roof of the infracenomanian sand increases gradually towards the West of the prospect area (>30 m). The transverse resistance (Tr) map shows that the identified aquifer has high values of Tr (Tr > 50000 ohm.m²) in the western part, corresponding to zones with relatively high thickness and may have high transmissivity. The longitudinal conductance anomaly (Sl > 0.6 ohm⁻¹) indicates that the area delimited by 1P2, 4P2, 1P4 and 3P4 VES points may have an important underground hydraulic potential. The interpretation of the acquired data also shows the presence of small depressions that could be implicated in the storage of the infracenomanian groundwater. Furthermore, the resistivity results reveal the presence of electrical discontinuities interpreted as faults and fracture zones. These could be the preferential axes of the groundwater circulation.
