Geology Of Saudi Arabia

The geology of Saudi Arabia includes Precambrian igneous and metamorphic basement rocks, exposed across much of the country. Thick sedimentary sequences from the Phanerozoic (including sandstone, anhydrite, dolomite, limestone, chert and marl) dominate much of the country's surface and host oil.

Geologic history, stratigraphy and tectonics

Saudi Arabia is underlain by the Precambrian igneous and metamorphic rocks of the Proterozoic Arabian Craton. Up to of sedimentary rocks from the Cambrian through the Pliocene and the Persian Gulf region.

Paleozoic (539-251 million years ago)

of Paleozoic rocks are exposed in the northwest, with the lowest correlated with the Cambrian in Jordan. The top is limestone, although most units from the Ordovician, Silurian and Devonian are terrestrial sandstone or shale.

Mesozoic (251-66 million years ago)

The Triassic begins with the Khuff Formation shallow water limestone and ascends through of Jurassic shelf limestone and marine shale, overlain by fossil-rich rocks from the late Jurassic and early Cretaceous. Jurassic rocks form much of the escarpment in central Saudi Arabia, although discontinuous sedimentation led to the deposition of calcarenite and anhydrite. The alternating layers of the Arab Formation took shape during the time and hold extensive oil and gas resources. The Kimmeridgian age Jubaila Limestone contains the high productivity Arab-D member in the Ghawar oil field and a -long sequence of aphanitic and calcarenite limestone. It often weathers to prominent scarps without talus.

For the most part, Middle Cretaceous rocks include thick sandstone, although some marine rocks are present to the north and Jordan. A combined sequence of of limestone and dolomite spans the Cretaceous into the Paleogene.

Cenozoic (66 million years ago-present)

The Umm er Rhaduma Formation, named by S.B. Henry and C.W. Brown in 1935 is the oldest Cenozoic sedimentary unit in Saudi Arabia, from the Paleocene to the early Eocene. It is visible in the walls of Wadi al Batin and overlies the dolomite and limestone of the Aruma Formation. The formation spans 1200 kilometers from Wadi Jabaliyah to the Iraq-Saudi Arabia border. Karst commonly forms in the uplands along with river channels. Northwest of Al Batin, the rock has very poor internal drainage. Drilling revealed two monocline structures were related to the dissolution and collapse of anhydrite layers. Dolomite, limestone and chert with some fossiliferous units are particularly common. Dissolved hydrogen gas renders water from the unit poor quality near Ras Tenura, Abqaiq and Nariya. Saudi Aramco developed the unit to supply water to its outlying operations.

The unit formation is overlain by the early Eocene Rus Formation, named for Umm ar Ru'us. Originally known as the Chalky Zone, it was renamed in 1946. It occurs only a few places, extending 180 kilometers north of Wadi as Sahba and occupying the breached center of the Dammam Dome. Chalk and limestone ascend to gypsum-bearing and calcareous shale. Coastal Saudi Arabia was only submerged briefly in the Cenozoic, limiting marine deposition, although the few Miocene and Pliocene marine rock are divided into the Dam, Hofuf and Hadrukh formations.

The early and middle Eocene Damman Formation is named for the Dammam Dome and includes basal marl, limestone and dolomite as well as the Saila Shale Member. It is exposed above the Umm er Rhaduma but largely overlapped by Miocene and Pliocene

HOME


Content is Copyleft
Website design, code, and AI is Copyrighted (c) 2014-2017 by Stephen Payne


Consider donating to Wikimedia



As an Amazon Associate I earn from qualifying purchases