Soft-linkage transfer zones: Insights from the Northern Eastern Desert, Egypt

Several soft-linkage transfer zones are well exposed and defined at the Northern Eastern Desert, Egypt. They are outcropped in the form of folds that soft-linking the overlapped ends of normal faults. These folds have several shapes and extensions which are easily pictured on satellite imagery. Detailed surface geological field mapping is carried out at Gebel Um Raqm to assess geometries and origins of these folds. Three main categories of soft-linkage folds are suggested in the present study. These are: (1) single fold soft-linkage (S-SL), (2) anticline-syncline pair soft-linkage (P-SL) and (3) multiple folds soft-linkage (M-SL). Structural analysis revealed that these folds represent relay ramps that encountered ductile deformation due to drag or reverse drag along the nearby planar or non-planar normal fault planes, respectively. The formation of the categorized folds is controlled mainly by dip polarity, geometry and overlapping/overstepping of the overlapped normal faults, in addition to mechanical stratigraphy and original dips of tilted beds. The findings of this research are attractive for the analysis of similar soft-linking folds at the subsurface and other outcrops worldwide as such folds have great significance in petroleum exploration.