Kimmeridgian soil is the principal soil type found in the wine areas of eastern Loire Valley, southern Champagne, and is at the heart of the Chablis wine region. The soil was identified by a French geologist Alcide d'Obigny, while working in Dorset near the town of Kimmeridge in the south of England in the middle 18th century. He encountered a unique layer of dark marl which he named Kimmeridgian.
Though it must be noted that the Kimmeridgian soils found in France differs from that found in England. As it is relatively uniform chalky marl with thin marly limestone containing layers and banks of mixed seashells. Strata from periods post the Jurassic period continued to be deposited into the shallow seas which covered this part of France.
Many of these layers were forced to the surface when the area known today as the Paris Basin began a slow dip during the late Tertiary and Quaternary periods. This slow tilting of the basin allowed the Seine, Aube, Yonne and Loire Rivers to erode, cut through the rising ridges of Kimmeridgian-Portlandian outcrop band into an archipelago of wine areas.
The Kimmeridgian outcrops, islands or sometimes called the Kimmeridgian Chain in that they are distinct and separate from their associated wine regions. The primary Kimmeridgian vineyard sites in France include: The Aube sub-region of Champagne, Chablis, Tonnerre, and Auxerrois wine areas of northern Burgundy; and the Pouilly, Sancerre and Menetou-Salon wine areas of the Loire Valley.
The success of the vineyards perched atop this chalky soil has been widely known for centuries. For just as long as anyone can remember, attempts have been made to duplicate their successes. Quality sparkling wine is now made in several places around the world, but it is not Champagne. The best wines of the Loire Valley still hold a haunting mix of terroir, fruit, structure and nuance that is impossible to duplicate elsewhere. And there are vibrant, refreshing Chardonnay’s made all over the world - but they are not Chablis.
It is thought Kimmeridgian soil is the most famous and important on earth when it comes to fine wine. The quality, longevity and unique features of this particular blend of limestone and clay have driven the wine world for centuries. There is simply no comparison.
A key to Kimmeridgian soil is the way it works with its Portlandian partner. The marly soil of the Kimmeridgian layer develops good structure and ideal water-retention and is easy to cultivate. The hard limestone of the Portlandian contains numerous fossils, fragments and is cracked by frost. This enables aeration of the gentle slopes as well as aiding in drainage.
Chablis is a ‘big island’ in the Kimmeridgian chain and is home to some of the finest Chardonnay known. The defined region was recognized in 1923 by the ‘Wine Tribunal’ as being grown on a sub-soil of Kimmeridgian limestone while wine grown elsewhere in Chablis would be classed Petit Chablis. The mid-slope in Chablis maps almost perfectly to the Kimmeridgian outcrop with the soft, carbonate-rich mud rock being covered by Portlandian limestone and supported by other limestone deposits. The south-facing Kimmeridgian slope also has significant sun exposure and is home to the Chablis Grand Cru vineyards.
The geologic conditions identical to those found in the Grand Cru slopes, also extend both northeast and southwest, but the vineyards on these sites are classed as Premiers Crus. This is an indication that Kimmeridgian soil is not the only ingredient in the making of a Grand Cru Chablis. As a matter of fact, the reference to Kimmeridgian limestone in the definition of Chablis was discontinued in 1976, as many believe it is also a combination of the slope and orientation of each site is of importance to producing quality Chardonnay in Chablis.
In the vicinity of Sancerre and Pouilly-sur-Loire wine areas of the Loire Valley, faulting has caused the east bank of the river (Pouilly side) to lower, thus causing the typical Kimmeridgian slope to lie flat, retaining elements of the Tertiary period - (containing sands, clays, and freshwater limestone) and Quaternary period - (containing high-river-terrace sands, gravel, and clay). The town of Sancerre sits atop a fault ridge, the eastern side is Kimmeridgian topped by Cretaceous soils while the west side is brush-covered gravel slopes. Further west the best vineyards sit on the classic Portlandian-Kimmeridgian combination.