Geology
DIFFERENT TYPES OF SOIL
Villiers limestones
These are sedimentary limestone deposits. They are made up from large quantities of white pebbles, generally flat and between 5 and 10 cm in size, enveloped in soil containing varying amounts of sand and clay depending on situation. These are well-drained soils that heat up rapidly in the spring, usually resulting in early maturing. They line the eastern part of the vineyard. They are found on the slopes around Villiers, to the east of Soumard and to the east and south of Bouchot. The old quarry at Vaurigny (with a lime kiln) is ideal for observing this soil structure
Villiers limestones
Marls with small oysters (Nanogyra virgula)
These are clayey-limestone soils, containing large quantities of "curly-shaped small oysters" and varying quantities of limestone pebbles and fossils (amonites) according to situation. More clayey than the previous types, these soil types take longer to warm up. They cover the largest part of the vineyard, the central part from Soumard, the area around Saint-Andelain (except the mound), Pouilly and part of Bouchot.
Marls with small oysters
Barrois Limestones
These are the second pebbly formation found in the vineyard; the limestone pebbles here are usually harder and larger than in the Villiers limestones. It contains few or no fossils. It is a very dry and poor soil. It is found on the western edge of the AOC area starting at Boisfleury and Boisgibault continuing up to the hamlet of Les Loges.
Barrois Limestones
Flinty clays
This is white, brown or greenish clay containing pieces of flint, varying in size from 5 to 20 cm. This formation is located on the heights of the Saint-Andelain mound, Saint Laurent and on the Tracy slopes.
Flinty clays
Argillosiliceous
More recent alluviums are also found, a mixture of sand, clay and silt which cover some limestone plateaux with thicknesses between a few tens of centimetres to several metres.
Argillosiliceous


SOIL FORMATION

From a geodynamic perspective the geological region is attached to the Burgundy plate. It is bordered on the west by the Loire trench which is juxtaposed with the Sancerre fault and the underlying Biturige immediately to the west.

The oldest lands are from the Jurassic period and are around 160 million years old. These are formed from calcareous marine deposits, with the fossils (remnants of organisms and shell debris) found in their heart testifying to their past life. Amongst these, the presence of corallum indicate that the climate at the time was tropical.

The sea receded from the area for the first time 140 million years ago, recovered it 20 million years later, then finally receded at the end of the Cretaceous period (70 M.a.), when the climate was colder than during the Jurassic period.

From this time onwards the area went through a strong erosive period. The calcareous deposits dissolved partially, leaving behind residues which were more or less clayey (flinty clays or cherts). A powerful Eocene river flowed from the Massif Central along the current bed of the Loire, leaving deposits in the north of the region (around Cosne). The climate was once more tropical during this period (35 M.a.).

An important tectonic phase then stretched across Western Europe from west to east. This created the Alsace, Bresse and Limagne trenches and in this region, the Loire trench. Many faults in a north-westerly direction appeared at the same time and sculpted the current hilly relief.

Four very different soil types can be differentiated in the vineyards:


 Villiers limestone of the Oxfordian

 Marls with oyster shells of the Kimmeridgian

 Barrois limestone of the Portlandian

 Flinty clays of the Cretaceous

M.a. Geological period Soil type Local name
113 CRETACEOUS Albian Clay-with-flint Silex (flint)
147 JURASSIC
SUPERIEUR
Portlandian Barrois Limestone Caillottes (pebbles)
156 Kimmeridgian Nanogyra Virgula marls Terres blanches (white soil)
163 Oxfordian Villiers Limestone caillottes (pebbles)

top