Caunes-Minervois - Geography and Geology

Geography and Geology

The town sits at the foot of the Montagne Noir which are themselves the southernmost extent of the Massif Central. The change in slope designates a change in geology from the predominantly metamorphic rocks of the nearby mountains to the alluvial deposits of the plains.

The settlement lies adjacent to the mountain river L’argent Double which can be a torrent after rain but usually has a gentle and semi-continuous flow, sometime disappearing completely below a bouldery riverbed. Highest flows are usually recorded in February falling away throughout the dry months. This river is a key attribute that lead to early settlement here, both in terms of the important pass created by its valley and the regular, sweet water supply. The river name l’Argent Double is purported to come from the Latin Argent meaning silver and Celtic dubrum, meaning water. Whether this refers to just the colour of a tumbling stream, the fact that the water is sweet (soft), or some other mineral content is not clear.

Figure 1. Map of the Montagne Noire. In the inset France is tan, the Massif Central is orange, and the Montagne Noire is purple (Roger, 2004).

The geology of the area has attracted considerable study and is fundamental to the position of the town:

1. the weakness in the rocks giving rise to the course of the river
2. the mountain pass following the river
3. the formation of the local marble through metamorphosis and
4. the subsequent development of complex local soil types allowing for a variety of vineyard terroirs

On a larger scale, the Montagne Noir result from the tectonic movements of ancient plates, ultimately resulting in the upthrust of the Alps and the Pyrenees. These mountain building events are known as orogenic periods, often named after the principal mountain ranges or ancient tribal areas in which the early geological research was undertaken. The Montagne Noire result largely from what is known as the Variscan (or Hercynian) Orogeny.

The local geology is complex with evidence of very old rocks from the Precambrian period being distorted and overlain with ocean sediments, which in turn have been involved in massive tectonic events. The changes to sedimentary deposits due to intense pressure and temperature effects have given rise to metamorphic rocks such as schist, gneiss & the economically important marble.

Granite outcrops can also be found relatively close (10 km) to Caunes adding complexity to the geology. It is expected that groundwater percolating though the acidic granite provides much of the soft water to the l’Argent Double in an area where hard water is more usual.

South, away from the metamorphic rocks of the mountains yet in close proximity, lie almost unaffected limestones, sandstones, clays and other rock forms. These are mixed with more recent alluvial deposits from the Aude valley.