Raymond’s Geology Blog
August 31, 2026

Geology and Mineral Resources – Seychelles

Introduction

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

A former French and then British colony, the Republic of Seychelles is a country of 97,617 people (121,355 in 2024) on an archipelago in the Indian Ocean east of Africa and northeast of Madagascar. The country consists of some 115 islands and has a total land area of 457 square kilometres. Other nearby islands include: the Maldives, Comoros, Mauritius, the French overseas departments of Mayotte and Réunion to the south, and the Chagos Archipelago to the east.

The Seychelles is a modestly prosperous country with a per capita GDP (PPP) of $21,940 and a very high Human Development Index of 0.848.The country has a developing economy where the main, non-government, economic activity consists of tuna fishing, tourism, rope production, boat building, printing, furniture making, beverage production, and agriculture. Agricultural commodities include coconuts, vanilla, cinnamon, sweet potatoes, cassava (for tapioca), bananas, and poultry. The public sector employs about 2/3 of the labour force and consumes about 1/3 of the country’s GDP. In 2024 the top exports of the Seychelles were fish, refined petroleum, and scrap copper. The top destinations for exports were the United Arab Emirates, France, the United Kingdom, Mauritius, and Japan. Also in 2024, the top imports of Seychelles were refined petroleum, frozen fish, passenger and cargo ships, recreational boats, and automobiles. The top origins for imports were the United Arab Emirates, Cyprus, France, India, and South Africa. Overall, in 2024, the value of imports ($1.63B) were greater than exports ($900M).

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

Geology

Figure 2 – Tectonic Evolution of the Seychelles
Credit: PetroSeychelles

The Seychelles are a microcontinent, a granitoid sliver, of the ancient supercontinent Gondwana, left stranded by the tectonic history of the region.

The oldest rock in the Seychelles are the Mahé and Praslin granites formed from the fractional crystallization of mafic magma This occurred during the Neoproterozoic Era, about 750 to 760 million years ago (Mya), and seems to have been the result of a period of post-collisional extension following the Pan African Orogeny, which brought together Gondwana.

The rocks that would eventually become the Seychelles sat at the heart of Gondwana for close to 500 million years until the first of three phases of rift tectonism began in the Late Permian. This tectonic rifting split Gondwana into western and eastern blocks opening up the proto-Indian Ocean and the Somali Basin during the Middle Jurassic and Early Cretaceous.

The second rifting event occurred during the Late Cretaceous when transform rifting separated East Gondwana into two blocks: Madagascar and a block made up of Seychelles and India. This lead to the formation of the Mascarene Basin as a portion of the Indian Ocean. Sedimentary deposition within the Mascarene Basin created a thick progradational wedge of sediment along the southwest Seychelles margin. This sequence consists of alluvial and fluvial deposits, overlain by lacustrine deposits, then shallow marine deposits and eventually open marine deposits.

The final rifting event, overlapping the Cretaceous / Paleogene boundary (yes, that boundary), separated the Seychelles from India. This rifting, coincident with the creation of the Deccan Traps, split the Mascarene Basin along first the Mascarene Spreading Ridge and then the Carlsberg Spreading Ridge, opening up the remainder of the Indian Ocean. The sedimentary accumulation within this new basin separating the Seychelles and India are mostly shelf carbonates.

Figure 3 shows geological maps of the Seychelles islands.

Figure 3 – Geological Maps of the main Seychelles Islands
Credit: Figure 1 in Shellnutt, Suga, & Lee, 2017
Creative Commons Attribution-Share Alike 4.0 International license

The main rock types found on the Seychelles islands are:

For more information on the Seychelles, follow up in the links above.

Paleontology

While there are undoubtedly fossils in the sedimentary deposits off-shore of the Seychelles, they are essentially inaccessible. However, on shore fossils on the Seychelles islands can be found in the Pleistocene aged carbonate rocks, the Aldabra Limestone, the Esprit Limestone and the Takamaka Limestone. Many of these fossils are various kinds of corals, as you might expect to find in a tropical limestone, but also vertebrates such as crocodiles and birds.

Here a few examples.

Aldabrachampsus dilophus

In 2004, the paleontologist Christopher Brochu found crocodile fossils on Aldabra Island that he called Aldabrachampsus dilophus. As crocodiles go, A. dilophus was a small animal growing to a length of between 2 and 2.4 metres, similar to the smallest living extant crocodilians. Despite its small size, there is evidence that A. dilophushunted, or at least scavenged, the Aldabra Giant Tortoise, Aldabrachelys gigantea,which still lives on Aldabra Island. A. dilophuswent extinct in the past 100,000 years.

Figure 4 – Crocodile Statue at the front of the Seychelles Natural History Museum,
Credit: Bjørn Christian Tørrissen, Creative Commons Attribution-Share Alike 4.0 International license

In more recent years, with the ability to now extract DNA from ancient bones, there was an attempt to determine the phylogenetic relationship of the Seychelles Crocodile with living crocodiles. In 2025, a team of paleontologists (Stefanie Agne, Patrick Arnold, Berthilde Belle, Nicolas Straube, Michael Hofreiter, and Frank Glaw) came to the conclusion that the Seychelles Crocodile was a subspecies of the well known modern Saltwater Crocodile (Crocodylus porosus). If they were anything like their modern relatives, it is not surprising that the Seychelles Crocodile went after tortoises.

Aldabrachelys gigantea

Figure 5 – An Aldabra Giant Tortoise at Beauval Zoo, France
Credit: Yotcmdr, public domain

Another fossil found in the Pleistocene aged Aldabra Limestone were early examples of the Aldabra Giant Tortoise, Aldabrachelys gigantea. Modern fully grown male Aldabra tortoises have an average weight of 250 kg while fully grown females generally weigh in at 159 kg. They are also long lived, like this one that lives at Plantation House on St. Helena and that was born in 1832.

Studies of the Aldabra tortoise have been useful in understanding the biogeography and dispersal of terrestrial creatures in the Western Indian Ocean. Let’s hope the turtles stay around for a while and not end up as somebody’s turtle soup.

Corals

Figure 6 – Acropora Coral off of Mahé Island, Seychelles
Credit: Diego Delso, Creative Commons Attribution-Share Alike 4.0 International license

Paleontologists have found many examples of fossil Scleractinia corals in the Pleistocene sediments of Aldabra Island. Identified species included: Acropora humilis, Acropora hyacinthus, Acropora lamarcki, Acropora muricata, Isopora palifera, Pocillopora grandis, and Porites nigrescens. Other corals that could only be identified by their genera included: Favia sp., Fungia sp., Galaxea sp., Goniastrea sp., Goniopora sp., Hydnophora sp., Leptoria sp., Platygyra sp., Pocillopora sp., Seriatopora sp., and Symphyllia sp.

And that’s just the corals that survived fossilization.

Coral reefs are incredibly complex ecosystems in the modern world, and there is no reason to believe that they were any less so in the past. One feature of this complexity is that various fauna on coral reefs are sensitive to environmental change resulting in the growth, and decline, in coral reefs during the Pleistocene.

Mineral Resources

Figure 7 – Granite rocks on the coast of Curieuse Island
Credit: NorbertNagel, Creative Commons Attribution-Share Alike 4.0 International license

According to the USGS 2020–2021 Minerals Yearbook on the Indian Ocean Islands, the Seychelles does not have significant mineral industry. The major mineral commodities are various forms of crushed granite from quarries on Mahé Island (you tour them see here and here). The most recent production statistics are here.

The USGS also notes that the Seychelles produced salt in 2024. This site describes the artisanal production of sea salt and its sale in local markets.

The Seychelles established a petroleum exploration company in 1984, but so far there has been no economic finds. In 2024 the USGS published Fact Sheet 2024-3010: Assessment of Undiscovered Conventional Oil and Gas Resources of Offshore East Africa and the Seychelles, 2022. The study estimated that there were undiscovered, technically recoverable mean resources of 5.1 billion barrels of oil and 79.1 trillion cubic feet of gas in offshore East Africa and the Seychelles. The most recent news articles on the oil exploration in the Seychelles are here, here, and here.

Summary

Figure 8 – Grand Anse Beach on La Digue Island
Credit: Tobias Alt, Tobi 87, Creative Commons Attribution-Share Alike
4.0 International, 3.0 Unported, 2.5 Generic, 2.0 Generic and 1.0 Generic license

There seems to be limited opportunities for mineral exploration and development in the Seychelles. While there may be oil and gas off-shore, as the USGS indicates, there doesn’t seem to be much interest in exploration. That could change, so it’s worth keeping an eye on.

On shore, artisanal salt production seems to be enough to satisfy local demand, so there is limited opportunity there. The market is a fickle thing; selling something that is rare or exotic, like salt from a remote island group like the Seychelles, might appeal to certain people.

As for the granitoid and syenite rocks that make up the Seychelles bedrock, its worth noting that they are not uniformly the same. Consequently, there is room for more study. While I couldn’t find any references to their occurrence, I wonder if there are any pegmatites on the islands? It could open up possibilities. Further study of the bedrock in Seychelles could be interesting for academics, at the very least.

Other than that, the Seychelles appears to be a well managed country and a good tourist destination. So there’s good reason to be optimistic for the place.

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.