The present study deals with the basement, Conrad and Moho discontinuity depths through nine 2-D density crustal modeling covering almost the Bouguer gravity map of the northwestern part of the Western Desert. Besides, the work is supported by the spectral analysis technique for depth estimation in addition to the fault trend analysis.
The depths obtained from the spectral analysis and the basement depth from the drilled well(Umbarka-1), in addition to subsurface geological information from about twenty drilled wells are aided in construction of the crustal modeling profiles. Consequently, three depth maps for the basement, Conrad and Moho discontinuities are constructed. These maps indicate that the study area is subdivided into two distinct tectonic blocks of different crustal type, evolution and isostatic characters; these are the southern and the northern blocks. The basement depths, generally, increase from the south to the north, it reaches about 3-4 Km in the southern parts to more than 7 Km in the northern (offshore) parts. In contrast, the Conrad and Moho discontinuity depths increase from the north to the south, where the Conrad depths are about 12 Km in the northern (offshore) areas to more than 19 Km in the southern (continental) parts. Mohole discontinuity depths reach about 24 Km in the marine areas to more than 32 Km in the southern continental areas. The areas between the southern continental block and the offshore oceanic one (along the coastal plain) are transional zones.
Results of trend analysis indicate that the area is greatly affected by six fault trends; they are E-W, NE-SW, WNW, NW-SE, N-S and NNE trends. The first three trends are the main controlling trends of the basement rocks and rejuvenated through the geological history of the area with the other three trends. The area attains also a number of sedimentary basins separated by high areas and trending mainly E-W, NW-SE and NE-SW.