Seeking to define what makes their terroir unique and understandably tired of seeing the word "Chablis" indicating all kinds of wines on the planet, at the end of the 19th century, the wine growers of Chablis found a reference that seemed safe to them, thanks to Father George Chappaz (1904): the Kimmeridgian. This refers to several geological strata belonging to the Upper Jurassic,150 million years ago. The rock base has a special characteristic: the abundance of a family of tiny oysters called Exogyra virgule, in the marls and the marly limestone. The Chablis vineyard is situated on these marls below the layer of Portland limestone (prolongation of the Côte des Bars in the Barrois): a landscape that typically has tree-crowned hillocks overlooking the vines.

Chablis is the only AOC vineyard to make express reference to a geological reality. Indeed the legal decision of 1923 indicates the Kimmeridgian as being an essential element of the best Chablis wines. The AOC everywhere were to take up former rulings, including this one. Scientific opinion has apparently evolved since then. In 1962 and 1967, international scientific conferences (without any relationship with the vine) added several tens of million years to the geological strata called Kimmeridgian. Moreover, more precise studies show than while certain non-Kimmeridgian soils are perfectly suitable for Chardonnay, some Kimmeridgian soils sometimes produce less fortunate results. This does not detract from the importance of retaining the long-standing desire to link the appellation to a precise geological origin, nor can it alter the fact that Chablis Grand Cru, the standard-bearer of the vineyard, is authentically Kimmeridgian in character.

Although Chablis is dry, limpid, full of bouquet, lively and light, unlike any other child of the Chardonnay grape, if, in a word, it has love, it is because of the link that ties the stock to its soil.

The Tonnerrois vineyard lies on somewhat older Oxfordian limestone strata close to Chablis.