干旱区生态环境知识资源中心

Geoelectric techniques have been used to detect and define the subsurface stratigraphy and structures around Hibis Temple in Kharga Oasis, Egypt. We used 2D and 3D inversion approaches to interpret the data set obtained from 20 dipole-dipole resistivity profiles with electrode spacings of 3 and 5 m and lengths between 39 and 85 m.

Five vertical electrical soundings, with a maximum array length of 200 m, along a profile crossing the study area were also carried out. A preliminary quantitative interpretation of the vertical electrical sounding curves was achieved using two-layer standard curves and generalized Cagniard graphs. The final models were obtained by ID inversion using the results of the manual interpretation as initial models. Model results were used to construct a georelectric cross-section that correlated very well with the stratigrapfiic units.

Five geoelectric units were identified: the first (the uppermost) is a high-resistivity layer consisting of fill deposits (rubble); the second is a muddy clay with moderate resistivity values; the third is also a muddy clay but with decreased resistivity due to the increase in salt content originated by the evaporation of the groundwater seepage; the fourth unit, at a depth of 7-13 m, is a muddy clay saturated with water seepage from the agricultural areas surrounding the temple; the final unit is a more resistive layer corresponding to dry muddy clay. The differences in the groundwater level, and its salt content, correlated with the irrigation activities around the temple. We concluded that the high corrosion potential of the seepage water might be connected with its salt content.