Structural characteristics of updip sides of half grabens and effect of pre-rift structures on rift geometry: northeastern part of the Suez rift

Abstract

Detailed field mapping of the Sudr block (updip side of the northern half graben of the Suez rift) indicates the presence of an early rift-facing flexure between the half graben and the eastern rift shoulder. Continued subsidence of the rift and/or uplift of its shoulders led to the upward propagation of a planar normal fault through this flexure. Pre-rift structures (“Syrian arc” folds) in the northern part of the rift led to significant offsets of the rift and its bounding faults and helped terminate the northern part of the rift near Suez city where extension is transferred to the area lying northwest of the Gulf of Suez. The listric normal faults bounding the northern and central half grabens of the rift did not dissect the steep flanks of these asymmetric pre-rift folds and were terminated against these flanks, perhaps due to strain hardening of pre-rift rocks in these flanks during the pre-rift deformation. The location of the accommodation zone between these two half grabens is therefore determined by these pre-rift structures.