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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 56 (1972)

Issue: 5. (May)

First Page: 882

Last Page: 902

Title: Geologic History of Nukhul-Baba Area, Gulf of Suez, Sinai, Egypt

Author(s): El-Sayed El-Tarabili (2), Nabil Adawy (3)


A study of the Nukhul-Baba area, on the eastern margin of the Gulf of Suez depression, shows that its present structural configuration is primarily the result of successive phases of tension faulting related to the subsidence of the present Gulf region. Fault directions are inherited from basement trends in the lower and upper Gattarian granites and Mitiq series rocks.

Tension faults form five systems. The most prominent one parallels the general direction of the Gulf of Suez and the Red Sea. The systems become progressively less prominent as their deviation from the Gulf of Suez direction increases. Accordingly, faults perpendicular to the Gulf are scarce. Statistical analysis indicates a selective rejuvenation of the tectonically weak directions of the basement, the most active direction being that parallel with the Gulf trend.

Strike-slip faults are very subordinate and are associated with a bending fold produced by local minor compression. Folds are produced mainly by drag or by tilt and drag of fault blocks. In addition, flexures and a bending fold are present in the area.

Analysis of the microstructures of the different stratigraphic units reveals the persistence of two b-fabric axes of 18 and 145° average strike directions. Both axes represent R (rotation)-tectonites. The 18° axis was found in only one case as a fold axis, whereas the 145° axis generally is present as fold axes, but the enclosing folds are mainly due to drag or tilt and drag of fault blocks. Both axes parallel the major rifting directions in the Gulf of Suez and probably are related to slight compression of the subsiding fault blocks. The 18° axis was not formed by Gulf of Aqaba rifting, but by Gulf of Suez rifting, and was produced because of the irregular downthrow and the nonsynchronous development of the major faults along the margins of the Gulf.

The tectono-sedimentational evolution of the platform sediments in the Nukhul-Baba area shows a recurrent sequence of events. Subsidence associated with faulting brought the area or parts of it to sea level. During the periods of sedimentation the faults were active and are, therefore, responsible for the deposition of more than 7,000 m of sediments only a short distance from the shoreline. After each period of sedimentation (i.e., period of faulting and subsidence), regional uplift took place. In addition, as the lithologic variations of the different formations reveal, oscillatory epeirogenic movements interfered during the subsidence and uplift phases. The spans of subsidence and faulting were (a) Cambrian-Late Carboniferous or Permian; (b) Cenomanian-Late Eocene; (c) Aquitanian(?) Helvetian; (d) Plio-Pleistocene; and (e) probably Pleistocene-Holocene.

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