A structural analysis of the El Kasr structure in the western desert of Egypt

The El Kasr structure was studied in order to investigate the origins and evolution of the enigmatic Desert Eyes structures of the Western Desert due to its accessibility and uniqueness among the structures. The El Kasr structure, an elongate structural basin with low limb dips, is unique among the Desert Eyes structures in that it: 1) occurs in isolation in otherwise horizontal sedimentary rock, 2) the long dimension of the basin is oriented NNW, 3) it is closely spatially associated with the less common NNW fault zones, and 4) is composite in nature. The structure was investigated using remote sensing and field mapping techniques. The structure is defined by basins of prominent carbonates and associated siliclastics. Both basins defining the structure have broad interlimb angles. The structure is truncated along the southwest by a prominent normal fault zone. Evidence for an eastern fault system includes truncation of layers of Dakhla Formation that strike at a high angle to the structure and terminate along possible drag folds and layers of Dakhla Formation that are locally steeply dipping, offset by numerous small faults, and rotated from the strike of the basin. The El Kasr structure occurs in the hanging wall(s) between two fault systems, which appear to merge south of the structure, as an elongated basin sub-parallel to the trace of these faults. Balanced cross-sections of the structure suggest that the El Kasr structure formed within a transtensional zone between overlapping left-lateral strike-slip zones. The sedimentary cover within this zone deformed by drape folding along the margins of the transtensional zone as well as plastic deformation over a graben that developed in the Precambrian basement. The investigation of the El Kasr structure suggests that other Desert Eye structures may have formed through interactions between fault segments and deformation related to rheology --Abstract, page iii