A flat country between two waters, where the land’s end faces the sea. This is how the Médoc appears to one who discovers it for the first time, once their awe has subsided over the scope and opulence of the great wine estates that line its riverbanks.
In the spring of 1787, during a brief stay in the region, Thomas Jefferson, then US Ambassador to France and future third President of the United States, compiled a list of the best wines he had tasted there on the advice of the United States consul in Bordeaux. In his travel diary he recorded numerous sage observations about the gravel soils of the great vineyards he visited.
But what are the origins of the gravel soils whose exceptional qualities were at last being recognised in this era, marking a poetic revenge of rock over marsh, of land over sea? On a geological scale, these are young soils, formed in the last million years during the Quaternary Period as a result of the planet’s alternating hot and cold phases. During each period of warming, water levels rose not only in the sea but in rivers like the Dordogne and the Garonne, while glacial ice break-up in the Massif Central and the Pyrenees would carry away rocky debris far downriver, resulting in the deposit of this gravel over the Médoc’s unique limestone substratum.
The ancient bedrock of Guyenne is a form of “asteriated limestone” – also known as “Bordeaux stone”, for having been used to build the city – and owes its scientific name to the myriad tiny “bones” one finds within it – vestiges of starfish from the genus Asterias. This bedrock’s marine origins are also evinced by the presence of oyster and coral fossils. “The sea, which covered the entire region during the Tertiary Period, played an indirect role in the creation of a terroir favourable to grapevines, since it created a limestone substratum that was sufficiently loose for the gravel to be deposited at a depth of around fifteen metres,” explains David Pernet, an engineer and wine consultant. “When the ice returned, the sea level dropped by tens of metres. Erosion cut into the gravel deposits and canyons were formed. The reshaping of these gravel deposits into rolling hills was therefore the result of fluctuations in sea level.”
And so took form the Médoc landscape – but the influence of maritime geology does not stop there: “During warm periods, when the sea level rose again, sometimes even higher than it is today, the tops of these rises became like dunes surrounded by brackish sea inlets, with frequent silting. These gravel terraces were thus enriched with fine clay particles.”
Of course, the predominant quality of this terroir remains the presence of gravel brought by the rivers. But the Médoc’s temperate oceanic climate, and the thermal inertia the surrounding water masses create here, also play a major role in the profile of the wines. The narrow range of temperatures fosters the preservation of acidity. Moreover, on the most renowned terroirs, such as that of Château Palmer, with their very compact gravel and clay soils, the vine’s roots struggle to reach great depths and must obtain water primarily from capillary rise. Thanks to this distillation process the vines are very often thirsty, but they are rarely too thirsty. “This exceptional combination, that of a temperate oceanic climate and a type of soil capable of causing hydric stress while moderating it, is found nowhere else,” enthuses David Pernet. Which explains why beyond the Médoc, Cabernet, a grape variety which needs hydric restriction to fully express its tannins, can often yield wines around the world that may be very powerful but which lack the balance they are able to achieve on the Médoc terroir.
“Things seem to be accelerating in an inexorable way of our own making, because humans have this capacity to create as well as to destroy…”
Thomas Duroux — Director,château Palmer
“In 2004, when I arrived at Château Palmer, I didn't immediately realise that I was to be working with mountain soils. Because discovering the Médoc terroir begins first and foremost with studying these rolled pebbles and hills, and it takes time for the realisation to sink in that all this gravel was deposited here as a result of climatic alternations.” says Thomas Duroux. And coming to terms with this reality is not eased by the further realisation that the terroir was also born from the sea – and that it will surely disappear back into the sea one day. “I like the idea of it being ephemeral – ephemeral in terms of geological time, not on a human scale. Certainly, if Palmer's terroir were to disappear in the next thirty years I would experience it as a tragic event. But to think that it will happen in a few thousand years, I think that’s beautiful. It shows that terroir truly is a living thing. Because in life there is always birth and death.”
Faced with global warning, subject to a greenhouse effect exacerbated by rising carbon emissions, disturbances are already occurring on the ground, which the men and women of the vineyard are constantly working to contain, even as they admit their many uncertainties: “Our climate here is dependent on the fact that the Gulf Stream from the Gulf of Mexico warms the Atlantic Ocean all the way to our shores. If it were to shift away from the coasts, we could see a winter cooling,” posits David Pernet, who nonetheless wagers that the most commonly evoked hypothesis is more probable: “If we assume that we are heading for a major warming, we could return to the temperatures we had during certain interglacial periods, and the sea level may come close to covering some of our gravel slopes, in which case they would no longer have the same capacity for drainage.”
For Thomas Duroux, it’s helpful to remember that global warming is not a catastrophe for the earth, only for humanity. The earth is expected to continue rotating for another 4 billion years, which means that our coastlines will surely be drawn and redrawn a great many more times. And one thing is certain: since the earth is the blue planet, covered with oceans, water – and with it, life – will never be far away.
