Crustal modeling of south Sitra area, north Western Desert, Egypt using Bouguer gravity data

The present study deals with the investigation of the nature (depth, density, thickness and topography) of the earth's crust and the upper mantle of south Sitra area, north Western Desert through the application of spectral analysis and 2-D gravity modeling techniques on the Bouguer gravity data of the studied area. The average depths to the major density interfaces (Basement surface, Conrad and Moho discontinuities) expected throughout the crust are determined from the spectral analysis of the Bouguer anomalies along 20 selected profiles covering the study area. In addition, the approximate depth to the upper basement surface, as the shallowest interface, has been estimated along 31 short gravity profiles using four spectral analysis techniques. Moreover, the Bouguer gravity anomalies are used with the available geological and geophysical information to construct two dimensional (2-D) gravity models of the earth's crust along six profiles trending in NW-SE, N-S, and NE-SW directions. From these models, three maps for the basement surface, Conrad and Moho discontinuities were constructed. The obtained results from these 2-D crustal models and maps indicate that: 1) the crust beneath the area comrises two igneous layers: upper and lower crust underlain by upper mantle basaltic layer. 2) The depth to the basement surface; thickness of the sedimentary section; ranges between 2.8 at the south central and north western parts to more than 5.0 km. at the northern, southeastern and southwestern portions. Meanwhile, the depth of Conrad discontinuity; thickness of upper crust; varies approximately between 19.50 and 22.70 km. Where, the Moho depth; crustal thickness; ranges from 32.0 to 34.90 km. 3) the average densities for the different rock layers are: 2.43 gm/cm³ for sediments, 2.74 gm/cm³ for the upper crustal layer, 2.93 gm/cm³ for the lower crustal layer, and 3.28 gm/cm³ for the upper mantle layer.