DEFINITION OF PHYSIOGRAPHY

Igneous and metamorphic rocks of Pre-Cambrian age are

exposed only in the Southern Mountainous Region. These

rocks belong to the Arabian-Nubian shield, which was

assembled during the Pan-African orogeny (1,200–500 million

years ago) as island arcs coalesced and extend as basement

underlying the sedimentary cover rocks. The basement

is deeply buried (7,312 feet; 2,174 m) at Nakhl, < 10,000 feet

(3,280 m) at El Khabra, as the thickness of the cover increases

to the north.

The southern mountains attain a maximum elevation of

8,665 feet (2,641 m) at St. Katerina, and several other peaks

exceed 6,560 feet (2,000 m). The eastern margin of the

southern province borders the Gulf of Aqaba and is characterized

by a poorly developed coastal plain, consisting of

scattered small deltas. This is due to the great depth of the

narrow Gulf of Aqaba (3,280 feet; 1,000 m), which prevents

the building of a coastal plain by coalescence of deltas. In

contrast, on the western margin, the older and relatively shallow

Gulf of Suez (984 feet; 300 m) has allowed the formation

of a broad coastal plain, as sediments eroding from the shield

have been deposited in alluvial fans and deltas.

The southern province displays several sets of prominent

lineaments that are clearly visible in satellite images. The lineaments

interpreted as faults are the result of tectonism that

both pre- and post-dates the deposition of the sedimentary

cover. The lineaments are marked by intermontaine valleys

that carry the weathering products to the gulfs on either side

of the peninsula. Basaltic dikes, most of which are related to

the opening of the two gulfs and the Red Sea during the

Miocene, are also seen as either positive or negative lineaments

on satellite images.

The Central Tablelands are comprised of two plateaus.

El Tih (“the wandering”) is the southern plateau, and El

Egma is to the north. El Tih is a horseshoe-shaped (concave

to the north) series of connected topographic highs (cuestas)

(maximum 5,250 feet; 1,600 m) which are separated from

the southern mountains by the Ramlet Himeiyir depression.

The plateau is composed of Cretaceous limestones, with

shales and sandstones at the base. The exposures of the lower

Cretaceous (Nubia-type) sandstone at the base of the southern

escarpments of El Tih are considered the principal

recharge areas for this aquifer.

On El Egma plateau, massive carbonate rocks of Eocene

age, containing bands of flint, are exposed in a broad zone

that dips gently to the north and occupies most of the middle

third of the peninsula. The plateau is separated from El Tih

plateau by three tectonic depressions: Yaraqa on the west, El

Aqaba on the east, and El Kuntilla on the northeast. El

Egma is drained by Wadi El Arish, the tributaries of which

create a well-developed and very complex network of

ephemeral streams. Between the Central Tablelands and the

Coastal zone (described below) lies a northeast-southwest

trending belt of folded sedimentary rocks disposed in anticline/

syncline pairs. These structures form prominent hills,

which rise up out of the surrounding limnic, alluvial and

aeolian deposits that fill the intervening synclines. The anticlines

are generally accompanied by brittle faults, probably

coeval with the uplift.

Three sub-belts can be defined, with the degree of deformation

decreasing to the southeast. The Gebel El Maghara

anticline is the principal feature in the northernmost belt and

is characterized by Jurassic sandstones exposed in the core

and on the northern flank, northwest-dipping axial surfaces,

doubly plunging hinge lines, intense brittle deformation, and

thrust faulting with overturned bedding on the southern

flank. Gebel Maghara has considerable exposures of Nubian

sandstones of lower Cretaceous age (Aptian-Albian) surrounding

the inner core.

The Giddi-Yelleq-Halal anticlines mark the second anticlinal

axis. The Nubian sandstone is also exposed in the cores

of these structures, although there is a lesser amount of erosion

of the core, as compared to Gebel Maghara. The syncline

between the Maghara belt and the Giddi-Yelleq-Halal

belt consists of Eocene rocks covered by unconsolidated Quaternary

sands. The syncline to the south of this belt is occupied

by lacustrine and alluvial deposits in Wadi El Bruk and

the central portion of Wadi El Arish.

The southernmost belt consists of approximately 15

small hills that are much less prominent but have steeper dips

than the northern folds. The hills lie in the midst of a northeast-

southwest trending fault zone, the Minshera–Abu Kandu

shear zone. South of the Minshera–Abu Kandu shear zone,

the roughly east-west trending dextral strike-slip Zarga El

Naab fault marks the southern border of the deformation

associated with the Syrian Arc. Some authors refer to this

fault as the Ragabet El-Naam fault. South of this fault, the

plateaus are undeformed, except for brittle fracturing and

faulting associated with the opening of the Red Sea and the

gulfs of Suez and Aqaba. Although well defined in the east,

this fault becomes obscure in the middle of the peninsula.

The synclines associated with the above-mentioned

anticlines are poorly exposed. In general, the synclinal axes

form wide plains that are covered by alluvium and lacustrine

deposits. These are underlain by Tertiary sediments

and are the location of the agricultural activity in the interior

of the Sinai. The synclines receive drainage from the

anticlinal blocks and in some cases are the locations of

“basins of interior drainage.” Drainage within these basins

does not join with the exterior drainage (that which empties

into the sea).

The Mediterranean Coastal Plain Region extends the

entire width of northern Sinai (approximately 118 miles; 190

km). The region is bounded on the north by the Mediterranean

Sea and on the south by the ridge of Gebel Maghara.

The present form of the land is due to the deposition and

subsequent reworking of Nile deltaic sediments during a

marine transgression in the late Pliocene and Pleistocene. Several

subsequent phases of regression resulted in the stranding

of the paleoshores, most of which have been reworked by

aeolian processes.

The region is divided into two main low areas, separated

by a ridge, the Bardawil Coastal Promontory. The western

area consists of low, rolling hills that have seen considerable

military activity, rendering the area unsafe for travel. In the

east, the towns of El Arish and Rafah lie among the coastal

dunes, which tend to increase in height up to 200 feet (60 m)

to the south and east.

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