The Neoproterozoic Rocks

The sedimentary cover is located east of the igneous and metamorphic basement of the Arabian Shield, and occupies about two thirds of the land area of Saudi Arabia, or about 68% with an estimated total area of 1,320,000 km2.

The sedimentary cover as a whole is a residual part of the Tethys Seaway, which resulted from the general and combined effects of sedimentary processes and tectonic movements around the Arabian Shield.

The sediments of continental and marine provenances were intermittently deposited and aggraded into an eastward thickening sequence with a thickness reaching 7,000 m in the Arabian Gulf basin and in the Empty Quarter.

They dip from one degree in the oldest sedimentary sequences to less than half a degree in the recent sequences.

These sedimentary sequences were formed over a period of approximately 541 million years, from the end of the Proterozoic Era, and are exposed in the central areas of Saudi Arabia in the form of a curved belt with its bend pointing towards the eastern edge of the Arabian Shield.

The older sequences are mainly composed of sandstones and shales, whereas, the younger Mesozoic to Cenozoic sequences are dominated by limestones and shales with layers of basalt flows (Harrats).

The sedimentary cover in Saudi Arabia hosts the world’s largest hydrocarbon deposits and reservoirs, groundwater, and mineral deposits, consisting of non-metallic industrial minerals, such as bauxite, phosphate, clay minerals, limestone, dolomite, gypsum, silica sands, sandstone, and black sands, in addition to the base metals, etc. These sedimentary rocks may also contain radioactive elements, such as uranium, and rare earth elements that are associated with the phosphate deposits.