The Middle East is an area of widely varying geography and topography, mostly characterised either by low rainfall or full desert conditions. These present an abundance of engineering and environmental problems. It has diverse mineral resources of which only one—oil—has been developed on a large scale in modern times, Fig. 1.

Central to the area is the Arabian peninsula, which is geologically a prolongation of the African Continent. The various sedimentary and structural belts further east and north-east are peripheral to the edge of this old nucleus. It is, consequently, convenient to describe the region in terms of four parallel zones; the Arabian shield, shelf and the submerged sedimentary terrain of the Gulf; the Iranian coast and foothills; the mountain ranges of the Zagros; and finally the high Iranian Plateau. Geological columns through Saudi Arabia, Kuwait, Iran and Iraq are indicated on Fig. 3, and a generalised cross section shown in Fig. 4.

The Arabian peninsula has three major elements, see Fig. 2.

The westernmost element is the outcrop of the Crystalline Shield, which flanks the Red Sea from Jordan to the Yemen, widening to 400 km in a broad flat dome in west-central Saudi Arabia. The crystalline rocks have a peneplaned surface which dips gently eastwards beneath the strata of the Interior Homocline (see Fig. 4).

The sediments directly overlying the Crystalline Shield are the Palaeozoic clastics, which are succeeded by Permian and Mesozoic rocks, dipping gently northeastwards. The older Palaeozoics are undisturbed at outcrop, but appear to have

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