Abstract

The stratigraphical sequence includes Palaeozoic (resting unconformably upon a Pre-Cambrian peneplane), Mesozoic and Tertiary rocks. These were deposited uniformly over the entire region although in Egypt the succession thins towards the south. Miocene rocks rest unconformably on earlier strata with which they contrast sharply in showing remarkable facies changes closely related to structural movements. Igneous activity was on a subdued scale and confined to Oligocene times. Dykes generally run parallel to the main Clysmic rift trend.

Rift faulting was initiated in Oligocene and continued into post-Miocene times. In addition to major marginal faults there are many tilted blocks which typify the pre-Miocene faulting. On the west some of these were eroded down to Basement before the deposition of Miocene sediments. In the east many such blocks exhibit only slight erosion and were probably not uplifted until late Oligocene times. The eastern boundary is marked by synthetic faults with downthrows of 1000 metres or more, but in one restricted area there is a downwarp broken by antithetic faults. The Miocene is characterized by anticlinal flexures generally associated with rejuvenation of Oligocene faults. There is no evidence of lateral movement but many of the faults follow ancient Pre-Cambrian trends. On the Sinai peninsula trend-lines show a twofold directional pattern, parallel to the Gulf of Akada and Gulf of Suez respectively. The angle between them suggests a series of conjugate pairs, originating as transcurrent faults in response to north-south compression. If this was the case, such strike-slip movements ceased before the deposition of the earliest Palaeozoic strata. These are at least as old as Carboniferous.

The area seems to have remained insulated from the great movements of lateral shiftwhich are claimed for the Akaba-Jordan rift and which are considered to be linked with the divergence of the Red Sea and the counter- clockwise rotation of Arabia. However, there is evidence to suggest that, since Eocene times, there has been a growing divergence of the margins of the Clysmic rift towards the south, producing a small counter-clockwise rotation of Sinai.

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