July 27, 2026

Geology and Mineral Resources – Saudi Arabia

Introduction

Figure 1 – Saudi Arabia
Credit: Mapsland, Creative Commons Attribution-Share Alike 3.0 Licence

The Kingdom of Saudi Arabia (a.k.a The Kingdom) is a country of 35,939,806 people on the Arabian Peninsula. The country has an area of 2,149,690 square kilometres and borders on: the Red Sea to the west; Jordan, Iraq, and Kuwait to the north; the Persian Gulf, Bahrain, Qatar and the United Arab Emirates to the east; Oman to the southeast; and Yemen to the south. The Gulf of Aqaba in the northwest separates Saudi Arabia from Egypt and Israel.

The Kingdom is a wealthy country with a per capita GDP (PPP) of $78,815 and a very high Human Development Index of 0.900.The economy of Saudi Arabia is dominated by the production of oil and natural gas, accounting for approximately 22.3% of Saudi GDP and 55% of government revenue. As of April 2026, the top exports of Saudi Arabia were by crude and refined petroleum, ethylene polymers, telephones, and propylene polymers; the most common destinations of the exports of Saudi Arabia are China, South Korea, India, Japan, and United Arab Emirates. The top imports were: automobiles, refined petroleum, gold, telephones, and medications; the most common origins of the Kingdom’s imports were China, United States, India, United Arab Emirates, and Germany.

For more details on the country, check out the Wikipedia and Grokipedia articles on The Kingdom.

Geology

Figure 2 - Tectonic and Structural Features of the Arabian Plate
Credit: Figure 3 in Pollastro, 2003, USGS Bulletin 2202-H, public domain

Tectonically, Saudi Arabia sits on the Arabian Plate. The Arabian Plate of the shield is separated from the Nubian Plate by the Red Sea Rift, to the west. The Arabia Plate is separated from the Somalian Plate by the Gulf of Aden Rift, to the south. To the southeast and east, across the Owen Transform Belt, is the Indian Plate. To the northeast, the Arabian Plate meets the Eurasian Plate in a convergent boundary marked by the Makran Fold Belt and the Zagros Fold Zone.

As a general description, the geology of Saudi Arabia can be divided into two main divisions:

1. Proterozoic aged basement rock that outcrops in the west of the country; and

2. Overlying the basement are Phanerozoic age sedimentary platform deposits.

The basement rocks exposed in the western part of The Kingdom include:

• Ultramafic and ophiolitic rocks, such as the Darb Zubaydah ophiolite.

• The Baish-Bahah Group composed of metamorphosed basalt, tuff, and greywacke together with sedimentary and volcaniclastic rocks cut by igneous dykes.

• The Jiddah Group made up of metamorphosed andesite and andesite porphyry and including some diabase, slate, conglomerate, dacite, and marble; a granodiorite body intrudes the group.

Figure 3 - Simplified geologic map of the Arabian Shield in Saudi Arabia
Credit: Figure 1 in Gahlan et al, 2023

• The Ablah Group which consists of clastic rocks, limestone,dolomitic limestone and marble together with peralkaline granite, and syenite with interbedded volcanic rock.

• The Fatimah Group consisting of: a) a lower clastic unit of sandstones and siltstones; b) a middle carbonate unit of limestones, sandy limestones and marbles; and c) an upper clastic unit of siltstone overlain by upper pyroclastic deposits.

• The Al Ays Group, a sequence of volcanic and sedimentary rocks: conglomerate, minor marble, basalt, greywacke and some silicic tuffs.

• The Silasia Formation, a succession of metamorphosed volcanic and sedimentary rocks; mostly shale with thin-bedded limestone and thin alternate beds of jasper and hematite.

• The Halaban Group, mostly andesite and fine-grained diorite, with gabbro, basalt, and basalt porphyry.

• The Murdama Group, clastic sedimentary rocks and small amounts of limestone and volcanic rocks.

• Shammar Group, rhyolite and tuff intruded by fine grained granite in sills and dykes.

• J'Balah Gr, mostly volcanic rocks with some clastic rocks and limestone.

• There are also many granite and diorite intrusions in the Proterozoic rocks.

Figure 4 – Stratigraphic Column, Eastern Saudi Arabia
Credit: Figure 1 in Pollastro, 2003, USGS Bulletin 2202-H, public domain

The sedimentary sequence in the eastern part of Saudi Arabia is fairly complex. Here is a brief summary:

Paleozoic Formations

• Cambrian to Ordovician periods: Qasim Formation, sandstone and claystone; and Saq Formation, sandstone.

• Silurian Period: Qalibah Formation, shale coarsening-upward to sandstone; and Tawil Formation, coarse-grained sandstone

• Devonian Period: Jauf Formation, shallow marine sandstones; and Jubah Formation, sandstone.

• Permian Period: Unayzah Formation, coarse-grained sandstone; and Khuff Formation, sandy limestone.

Mesozoic Formations

• Triassic Period: Sudair Formation, sandy claystone; Jilh Formation, sandy limestone; and Minjur Formation, clayey sandstone.

• Jurassic Period: Marrat Formation, limestone; Dhruma Formation, clayey limestone; Tuwaiq Mountain Limestone, clayey limestone; Hanifa Formation, reef limestone; Jubaila Formation, limestone; Arab Formation; oolitic limestone; Hith Anhydrite Formation, anhydrite.

• Cretaceous Period: Sulaiy Formation, limestone; Yamama Formation, oolitic limestone; Ratawi Formation, claystone; Kharaib Formation, including the Hawar Member, reef limestone; Shu'aiba Formation, oolitic limestone; Nahr Umr Formation, claystone; Mauddud Formation, dolomitic limestone; Wara Formation, sand, shaley sand and shale; Ahmadi Formation, claystone; Rumalia Formation, limestone; Mishrif Formation, reef limestone; Aruma Formation, clayey limestone.

Cenozoic Formations

• Paleogene Period: Umm er Radhuma Formation, Rus Formation, gypsum and anhydrite; and Dammam Formation, clayey limestone.

• Neogene and Quaternary periods: undifferentiated formations including active sand dunes and coastal sabkha deposits.

This is a very limited look at the geology of Saudi Arabia. For more reading on the geology, you can follow up on the links above. You can also look into the USGS file on The Kingdom, here – there are 22 pages of links.

Paleontology

With its complex geology, Saudi Arabia also has many fossils. Here are a couple of examples.

Arsinoitherium

A large herbivore that lived during the Eocene and Oligocene epochs, Arsinoitherium is related to modern day elephants, sirenians, and hyraxes.Arsinoitherium ranged in size from 500 kg to almost 2,000 kg.

Figure 5 – Reconstruction of Arsinoitherium
Credit: Creative Commons Attribution 3.0 Unported license

Arsinoitherium fossils have been found in the Shumaysi Formation of Saudi Arabia.

Nummulites

Figure 7 – Nummulitesfossils
Credit: Wilson44691, public domain

A large foram, fossils of Nummulites are widespread in the deposits from the former Tethys Ocean. With numerous species, Nummulitesare important index fossils in petroleum exploration. Nummulites fossils have been found in the Dammam Formation.

Other interesting things about Nummulites:

• In 1913, naturalist Randolph Kirkpatrick published a book, The Nummulosphere: an account of the Organic Origin of so-called Igneous Rocks and Abyssal Red Clays. In the book, Kirkpatrick proposed the hypotheses that all rocks had been produced through the accumulation of forams such as Nummulites.

• In the Runescape game, Nummulites are a form of currency used on Fossil Island.

Mineral Resources

Figure 7 – Oil Rig in the Desert
Credit: Paul Palmer, public domain

The mineral industry in Saudi Arabia includes not only oil, but also many industrial and metallic minerals. Rather than go into all these various commodities, I am going to focus on three examples. You can look into the most current production statistics and production locations in this document from the USGS.

Ghawar Oil Field

Figure 8 - Location of the Ghawar Oil Field
        Credit: Figure 1 in Saner et al, 2005

The Ghawar Oil Field is the world’s largest oil field and produces substantial volumes of associated natural gas alongside crude oil. Here are some important features of the Ghawar field’s geology

• The structure that hosts the Ghawar field is a regional anticline, a drape fold over a basement horst, which grew initially during the Carboniferous Hercynian deformation and was reactivated episodically, particularly during the Late Cretaceous.

Figure 9 – Cross Section showing the Ghawar Field
Credit: Figure 8 in Afifi, 2005

• The source rock for the hydrocarbons in the Ghawar Field is the Jurassic aged Tuwaiq Mountain Formation.

• The primary reservoirs for natural gas are the sandstones of the Permian aged Unayzah Formationand the limestones of the Khuff Formation together with the shallow marine sandstones of the Devonian agedJauf Formation.

• The main reservoir for petroleum is the Jurassic aged Arab-D Limestone.

• At the top of the Arab-D series is a cap rock made up of evaporites.

• Water flooding has been used to enhance oil production in the Ghawar Field since 1965.

• There are concerns with the possible near future collapse of production from the Ghawar field, as outlined by the late Matthew Simmons in his 2005 book Twilight in the Desert: The Coming Saudi Oil Shock and the World Economy. I’ve read the book and he has made a strong case that the field is going to be depleted soon. But it’s a big field and there is still a lot of oil left in it.

Gold in Saudi Arabia

Figure 10 – Gold Specimen from Saudi Arabia
Credit: Meshari Alawfi, Creative Commons Attribution 4.0 International license

Before oil, Arabia was known as a source of gold. This has been true since ancient times. Currently there are a few gold mines in operation:

• Mahd adh-Dhahab Mine, an ancient deposit, the current mine opened in 1988. An underground mine, its shafts reach a depth of three hundred metres below surface. In addition to gold it produces silver and copper.

• The Al-Duwayhi Mine is the largest gold mine in the Kingdom. Production began in 2016.

• The Al-Amar Mine commenced production in 2009. It also produces copper and zinc sulfide concentrates for sale to external smelters.

• The Bulghah Mine is an open-pit mine that began operation in 2002.

• The Al-Sukhaybarat Mine is also an open-pit mine.

• The Al-Suq Mine is another open-pit mine. It began production in 2014.

Water Resources – Surface Water, Groundwater, and Unconventional Sources

Water resources are precious in most countries, especially so in a desert land like Saudi Arabia. All water resources - surface water, groundwater sources, and unconventional sources - are carefully managed. Here are a few highlights of the resource management.

• Surface water is harnessed in some 522 dams. These dams have a capacity to stopre approximately 2.3 billion cubic metres (BCM) to facilitate the storage and recharge of surface runoff and about 1.6 BCM/yr of the surface water is used.

Figure 11 - Principal Aquifers in Saudi Arabia
Credit: ©Fanack Water, Water Resources in KSA

• Shallow aquifers with renewable groundwater sources, are found in the Khuff, Tuwaiq Mountain, Aruma, Jauf, Sakaka, Jilh and Jubailaformations. The total renewable groundwater is estimated to be 2.8 BCM/yr.

• Deep aquifers, storing so-called fossil water, are found in the Saq, Wajid, Tabuk, Minjur-Dhurma, Wasia-Biyadh, Umm er Radhuma and Dammam formations. The average annual groundwater withdrawal rate is 20 BCM, while the annual recharge is only 2.8 BCM, so these aquifers have become gradually depleted.

• Unconventional water sources include water recovered from desalination plants and treated waste water. The total capacity from desalination plants was estimated at 7.4 BCM/d in 2020. Water from desalination plants meets approximately 70% of the water needs in the Kingdom. The current Iran War could target these plants.

• Waste water is also recycled in The Kingdom. The amount of treated wastewater reused in 2019 amounted to 4.9 million cubic metres per day.
  

Summary

Figure 12 – Sand Dunes near Riyadh
Credit: Meshari Alawfi, Creative Commons Attribution 4.0 International license

That wraps up this all too short look at the geology of Saudi Arabia. People have spent their whole lives trying to understand it and this short essay only scratches the surface. Follow the links for more information, there is a lot to read.

When it comes to mineral wealth, in many ways Saudi Arabia hit the jackpot, for example with gold and oil. No doubt they praise Allah for their good fortune. But good fortune comes with it own set of concerns.

Gold is an interesting example where it is in great demand among the people of The Kingdom, so much so that domestic production cannot meet the demand and they import gold, to the tune of approximately $8.08B in the last year. The desire for gold may just be cultural, a traditional store of family wealth, or may betray a deep anxiety about the future.

This is where the story about oil comes in. On one hand there is no doubt that oil wealth enabled The Kingdom to build a modern, prosperous, society. But, some day the oil wealth will dry up. Then what? Back to herding goats? Having gold in the bank might help ease the transition to a post-petroleum economy. So will developing nuclear power, as in the recent agreement on uranium enrichment.

As it is, present day Saudi Arabia is at the mercy of international petroleum markets. Rises and falls of the price of oil affects not only government revenues, but also the livelihood of ordinary people in The Kingdom, both citizens and foreign guest workers. It also profoundly affects Saudi Arabia’s geopolitical situation. Current day events, like the war in Iran add to their problems - it’s hard to sell oil when someone is cutting off oil transport routes. Things could get interesting in The Kingdom.

All things considered, I am optimistic for Saudi Arabia. They have been blessed with good leadership on top of their natural wealth. Good leadership is vital to survive in what is, in fact, a dangerous part of the world. I doubt that the House of Saud have forgotten how they took power in Arabia and how vulnerable they are if their leadership becomes lax. Nor can they ignore the many wars that have been fought in the neighbourhood. The Kingdom is deeply involved in the Iran War as an American ally and facilites in The Kingdom are targets. These are the things that keeps the leaders of The Kingdom up at night; they probably wish it was just the ladies of their harem that kept them awake at night.

For geoscientists, The Kingdom has many opportunities. They will be exploring for more mineral wealth – oil, gold, phosphates, and other industrial minerals. If you have a love of desert landscapes and a tolerance for living under Sharia Law, Saudi Arabia could be the place for you.

Standard Caveat

J. Robert Oppenheimer on freedom and scientific inquiry

The purpose of my weblog postings is to spark people's curiosity in geology. Don't entirely believe me until you've done your own research and checked the evidence. If I have sparked your curiosity in the subject of this posting, follow up with some of the links provided here. If you want to, go out into the field and examine some rocks on your own with the help of a good field guide. Follow the evidence and make up your own mind.

In science, the only authority is the evidence.