Geological history of the Limousin

The administrative boundaries of the former Limousin region broadly follow geological boundaries. For the most part, the region belongs to the Massif Central, defined as a collection of granites and metamorphic rocks dating from the Paleozoic era (539 to 252 million years ago).

At the beginning of the Paleozoic, what was to become the Limousin was entirely covered by the sea and was located in the southern hemisphere. Between 450 and 300 million years ago, an immense mountain chain (the Hercynian range) emerged, stretching for thousands of kilometers across Europe. From the end of the Paleozoic (-300 to -250 Ma), the Hercynian chain gradually eroded. The present-day bedrock of the Limousin corresponds to remnants of this chain. The result, at the beginning of the Mesozoic (-250 to -200 Ma), was a vast plain, sometimes submerged, sometimes emerged, home to vast tropical forests. The European continent gradually moved into the northern hemisphere.

Erosion of the Hercynian chain produced river-borne detrital sediments that formed the sandstones of the Brive Basin on the southern edge of the crystalline basement. Between -250 and -100 Ma, marine sediments (limestone and marl) were deposited in a shallow sea to form the Aquitaine Basin. By 150 Ma, Europe was almost where it is today.

Cataclysmic events such as the fall of a meteorite at Rochechouart (-207 Ma) and the eruption of the Cantalien volcano, whose basaltic flows reached eastern Corrèze (-10 to -6 Ma), enriched the geodiversity of the Limousin. The crystalline basement is still undergoing numerous upheavals linked to the formation of the Pyrenees and the Alps, which structure today's Limousin landscape.

Fault lines and deep valleys with vertiginous slopes can be seen throughout the region. They appeared 65 million years ago and were shaped by the melting of glaciers that covered the neighbouring Auvergne. Today, altitudes reach 800 or 900 meters in places, and throughout the region, numerous deep valleys with dizzying slopes, though very young in geological terms, interrupt a high plateau, while to the south, the Brive basin leads us via the Causse corrézien to the borders of Quercy and Périgord.

The main rocks of the Limousin

Brought to the surface by erosion, metamorphic and plutonic rocks now cover almost 94% of the Limousin's surface. Metamorphic rocks are the result of major transformations undergone by a variety of rocks in the depths of the Earth, where high temperatures and pressures prevail. They are represented by gneisses, micaschists, schists, serpentinites, amphibolites... Plutonic rocks, on the other hand, are rocks derived from various magmas that have cooled slowly at depth: granites, granodiorites, diorites, gabbros..

Granite is ubiquitous in the Limousin region, as you'll discover on your walks. Beige, pink, grey or blue, granite is used as rubble or ashlar, and is the traditional building material in the Millevaches region. The ruins of the Roman thermal baths at Les Cars, near Millevaches, bear witness to this ancestral use, which made the reputation not only of the materials used, but also of those who knew how to use them so well: the Creuse masons. Until the 1940s, monuments, official buildings and opulent residences were practically always built or adorned with cut granite of local origin.

It's worth noting that much of the granite used for construction did not come from quarries, but from the large erosion-resistant "balls" known as "solitary blocks" that dot the landscape here and there. Some natural sites are particularly worth a visit: the Pierres Jaumâtres granite chaos at Toulx-Sainte-Croix, the Rigole du Diable near Royère-de-Vassivière, the Chapelle du Rat at Peyrelevade, and the Rochers de Puychaud in the Monts de Blond, which mark the symbolic boundary between the Oc and Oïl languages.

Mineral extraction

Until recently, the Massif Central in general, and the Limousin in particular, were the site of numerous mineral extraction operations. These included lead and zinc, sometimes combined with silver or antimony, tin at Vaulry, tungsten near Saint-Léonard-de-Noblat and, above all, uranium around the Monts d'Ambazac, but also in Creuse and Corrèze.

Gold has also been sought and mined, mainly in the south of the Haute-Vienne (Saint-Yrieix-la-Perche), the north of the Dordogne (Jumilhac-le-Grand) and in the east of the Creuse, discontinuously from Gallic times to the beginning of the 21st century. A total of 37 tonnes of this precious metal were extracted.

Coal was deposited during the early stages of erosion of the Hercynian chain in lakes occupying small basins bounded by fractures in the basement (Bourganeuf-Bosmoreau and Ahun-Lavaveix in Creuse, Argentat in Corrèze...). Generally speaking, coal seams were geologically irregular and variable in quality, making them difficult to mine. Despite this, the Bosmoreau and Lavaveix mines continued to operate until after the middle of the 20th century (1958 and 1969 respectively). But all that remains today is the memory of those days, which you can discover in the mine museum at Bosmoreau-les-Mines.

The Rochechouart meteorite

The canton of Rochechouart is home to one of Europe's greatest geological curiosities. More than 200 million years ago, a meteorite measuring at least 1.5 km in diameter crashed into the earth at over 70,000 km/hr. In a matter of seconds, a crater 20 to 30 km in diameter and 1 km deep was hollowed out. The basement rocks and the meteorite volatilize, melt, are projected into space and fracture, giving rise to special rocks: impact breccias ( impactites, used in local construction). Today, the crater has been worn away by erosion, and all that remains of the collision is the crater floor. In addition to the impactites, veins of gold, quartz and serpentine are visible. For a long time, the site was a real enigma for scientists, and the impact was only recognized in 1974. This vast plain is overflown by many butterflies: peacock, Spanish tobacco, devil's robin, sylvain, azure and as many birds: oak jay, buzzard, common buzzard..

Important regional nature parks

Awareness of the value and fragility of these emblematic landscapes has led to the creation of two regional nature parks to protect them.

At the heart of the region, the Millevaches Regional Nature Park, a green lung covering over 3,400 km², is a wilderness wonderland. It covers the Millevaches plateau, which represents almost the entire Limousin mountain range, with altitudes ranging from 700 to 900 m, and includes Mont Gargan (731 m) and Mont Bessou, in Corrèze, and its twin, Puy Pendu, not far from Meymac, culminating at 977 meters. This natural area of 124 communes straddles the departments of Haute-Vienne, Creuse and Corrèze. Forests, peat bogs, moors, lakes, ponds, rivers, peaceful villages, bucolic lanes... it's all here! Several major rivers, including the Vienne, Creuse, Vézère and Corrèze, rise here before flowing into the Loire and Garonne rivers. The population of Millevaches is 12 inhabitants/km²... so you can look forward to moments of peace and quiet!

To the west of the Massif Central and south of the gentle Aquitaine region, the Périgord-Limousin Regional Nature Park covers an area of 1,800 km², straddling two départements: Dordogne and Haute-Vienne. Chestnut forests, white-water rivers, Limousin hedgerows, Perigord valleys and limestone plateaus, where orchids bloom in spring, make up a landscape of great diversity. This natural setting is home to exceptional flora and fauna, including 110 species of breeding birds and rare, protected species such as the yellow-bellied sounder, the guinea fowl and the European mink. In terms of hiking, the park boasts over 2,000 km of well-marked footpaths. It is also crossed by several GR trails, as well as by the routes leading to Santiago de Compostela.