DEFINITION OF TECTONIC HISTORY

The tectonic development of the Sinai began with the assemblage

of several island arcs during the Pan-African orogeny in

the Late Proterozoic and early Cambrian. These rocks are the

igneous and metamorphic basement complex that forms the

mountainous southern region. In addition to older fabrics

related to the assemblage of the complex, the basement rocks

have been affected by the Gulf of Suez rifting (north-northwest

trend), as well as by the left-lateral strike-slip faulting in

the Dead Sea–Araba Valley (north-northeast trend).

Sediments deposited in the Tethys Sea were buried and

compacted to become the sedimentary rocks of the Central

Tablelands of El Tih and El Egma plateaus. These rocks were

deformed by the closure of the Tethys basin. Deformation in

the southern portion of the central region is limited to faulting

and epeirogenic tilting (circa 4° N), whereas both folding

and faulting are seen in the northern part of the peninsula.

Two fault zones mark the division between the two

styles of deformation. The southern fault (Ragabet El Naam;

also referred to as the Zarga El Naab fault) is an east-west

striking, right-lateral, vertical strike-slip fault. The northern

fault zone (Minshera-Abu Kandu shear zone) is composed of

major faults with large (3,281-foot; 1,00-m) vertical displacements

that parallel the trend of the fold belt.

The Gulf of Suez began forming as a rift no earlier than

the Late Eocene (40 Ma). Three separate half-grabens

(northern, central, and southern) make up the rift zone. In

the northern and southern basins, the blocks are tilted eastward,

whereas in the central half-graben, the blocks dip to

the west. The Gulf of Suez is made up of a series of linked

pull-apart basins formed from the shifting of the Arabian

plate up to 65 miles (105 km) along the left-lateral Dead

Sea–Araba fault. This results in a westerly and clockwise

motion of the Sinai, which is acting to close the Gulf of Suez

by at least 15.5 miles (25 km).

The origins of the North Sinai fold belt are less than

clear but are widely regarded to be related to the Syrian

arc, the origin of which is also problematic but appears to

be the result of shortening of the upper crust as Arabia

rotated away from Africa. This caused compression in the

northern Sinai and extension in the south. The folding

began in the Late Cretaceous (Senonian), as the Tethys Sea

began to close, and continued to the Early Miocene and

may still be active.

See also ARABIAN SHIELD.

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