Fault-related folds at the central northern part of the Cairo-Suez District, Egypt: example from Gebel Um Raqm area

Abstract

Detailed surface structural mapping of the area positioned in the central northern sector of the Cairo-Suez District (Egypt) was carried out to define the fold geometry and structural evolution of the highly deformed area in an extensional setting. This work is accomplished via field observations of the surface structures and interpretation of the high-resolution satellite images. Stratigraphically, the outcropped rock units are differentiated into four main units and are represented by the Upper Eocene, Oligocene, Lower Miocene, and Middle Miocene formations. Structurally, the Gebel Um Raqm is divided into three main sectors: northern, central, and southern. The northern sector is defined by left-stepping en echelon E-W to WNW normal faults, while the southern sector is delineated by left-stepping en echelon NW-SE normal faults. Moreover, the central sector is characterized by horst-graben faulting styles and step-faults. The structural analysis of the area revealed four main fold trends, which are identified and represented by NW-SE, E-W, WNW-ESE, and NNW-SSE. Also, the major faults are grouped into four main trends and are represented by WNW-ESE, NW-SE, E-W, and NNW-SSE. The interpreted structural geometry of folds and faults indicates that these folds are developed either by the drag of ductile beds along the fault planes as drag folds or formed between the overlapped normal faults as transfer folds.