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Jurassic Terroir

Exploring the geology of Gigondas with consultant Georges Truc
Geologist Georges Truc gives a personal tour of Gigondas, from the Jurassic to today.
Photo by: James Molesworth
Geologist Georges Truc gives a personal tour of Gigondas, from the Jurassic to today.

Posted: Jul 12, 2018 3:00pm ET

Whether it's playing the blind tasting game or reviewing wines officially (in a blind tasting), the first thing I think about when I taste a wine is its structure and feel. That tells me where the wine could be from, and then I work backward, eliminating what it likely isn't in terms of varietal, climate, etc.

A fine thread of chalky minerality usually means limestone. A rigid, austere, cast-iron edge usually means schist. A broad swath of rounded tannins usually means clay. A perfumed and silky feel indicates sand. And so on … terroir is what fascinates me. And of all the terroirs I've seen, few fascinate me as much as that of Gigondas.

As dramatic as the Dentelles de Montmirail are (the jagged, teeth-like outcroppings that rise above the town and vineyards of Gigondas), the story of their creation is even better. Especially when it's told by Georges Truc. Truc, a spry and sharp 76 years old, is a former University of Lyon geologist with wine in his blood. Born and raised in nearby Visan, Truc's father bought grapes from neighboring growers and made wine at the family home. Today, Truc combines his love of rocks and dirt and wine to consult on terroir and soil maps for several of the Southern Rhône's appellations, including Châteauneuf-du-Pape, Costières de Nîmes and, of course, Gigondas.

"This area is a large sedimentary basin," says Truc, holding a piece of paper flat in front of him, representing Gigondas. "During the Jurassic period, that basin sunk," he said, folding the ends of the paper up and forcing the middle down. "This basin was filled with water to form a sea. During dry periods, it would evaporate, leaving limestone formed by ammonites and other organisms, as well as gypsum behind. During humid periods, rivers cutting through the area would carry fine sand and clay and deposit it in the basin. This resulted in layers on layers of sedimentary deposits."

"Then, around 65 million years ago, the major fault in the area, the faille de Nîmes, was active," he explains. "The Pyrenees and then Alps were formed and, in doing so, the pressure increased on these sedimentary layers, which were 8 kilometers deep. That pressure was so great that the layers of salt and gypsum were forced into a creamy-like mixture that was forced upward, pushing its way through 8 kilometers of clay and sand. The Dentelles were formed by this vertical movement, which then had the added effect of essentially flipping the basin on its side. That drew in water from the Mediterranean, leaving sandy deposits, while pushing the limestone and marl layers to the surface."

To demonstrate his point, we drive up into the Dentelles on one of its ribboned dirt roads. Coming to an opening between two sets of the Dentelles, we stop in a small vineyard parcel and Truc points to a rock wall of limestone cross-hatched with grooves.

"Here is the vertical and horizontal movement of this layer, from all that pressure. And next to it," he says as he moves a step to his right, "is a layer of marl, then another limestone layer, then marl, and so on. They are now vertical, like books that had been laying flat, now pushed upright."

"What makes this areas so unique is that every soil ever created in the last 230 million years [here] can be found here, because these layers that should be 8 kilometers below the surface are pushed up through the surface. It is essentially a geological island, with Gigondas in the middle," he continues. "And from there, the diversity of soils here is so crazy, not only because all those layers that should have stayed below were pushed up, but because, over time, rain washed sediments off the Dentelles and carried them down to the plateau below, mixing with the sand from the Mediterranean along the way."

Before, when I tasted Gigondas, I would typically get the fine chalky minerality and perfume I associate with limestone. That limestone is a wonderful rapier to the dark, smoldering black currant and blackberry flavors that form the typical Gigondas fruit profile.

Now when I taste Gigondas, I'll also taste 230 million years of geological history. And that's why wine is so cool.

Follow James Molesworth on Instagram, at instagram.com/jmolesworth1, and Twitter, at twitter.com/jmolesworth1.

Sean Gilbert
Yakima, wa, usa —  July 24, 2018 11:58pm ET
That is so cool! Thank you for sharing

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