After a regional presentation of the Gulf of Suez, a thermomechanical model of the rift evolution will be presented.

Then we will examine some structural problems related to extensional tectonics as the internal deformation of tilted blocks.

Two main types of deformation are generally considered in extensional terranes: (1) faulted blocks are rigid and deformation consists of translations and rotations; (2) blocks are pervasively deformed, by simple shear along closely spaced minor faults or by "flexural slip" parallel to bedding planes. To evaluate the amount of such pervasive deformation field measurements were performed across three major tilted blocks of the Suez rift (Abu Durba and Araba-Qabeliat blocks) and Red Sea (Duwi block). They consist of narrow (15 to 20 km wide) elongated (30 to 60 km long) monoclines dipping to the northeast and bounded by major southwest dipping faults which have vertical displacement of about 2 km. Tilt angles vary from 15 to 20°. Secondary normal faults are scarce, widely spaced and their throw comprises between 10 cm. to 150 m. No pervasive and closely-spaced faults with centimetric or metric throws have been observed.

In the Abu Durba and Duwi blocks the amount of extension due to secondary faults is less than 7% while it is almost null across the Araba-Qabeliat block. Extensional models inducing pervasive deformation of blocks by vertical or oblique simple shear are irrelevant when tilt angles do not exceed 20° and rigid rotation can be applied to restore the cross-section. Moreover, most of the observed secondary normal faults have the same dip direction as major bounding faults. This arrangement suggests that tilting occurs over a ductile crustal layer which accommodates at depth the volume problems caused by rigid block rotation.

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