Champagne Part 2: Geology

Disclaimer: This blogpost is not about the terroir of Champagne. Instead, it is about the geology of the region and why certain types of soils are good for growing grape vines.
Jennifer Hugget wrote in her research article: According to Chappaz (1955) ‘The winegrowers of old, although ignorant of the geology, always stopped their vineyards right at the contact of the two Chalk formations’ – the Belemnite (Campanian) and Micraster (Santonian) biozones and became an accepted ‘fact’, without any questioning as to why the vines should perform so differently in adjacent chalk zones of similar mineralogy.¹
What this vignette says to me is that these winegrowers had very keen powers of observation. Even though they knew very little about the underlying geological features in their vineyard, it was to the soil that they attributed the differences they saw in the growth of their grape vines.
But, what is it about Champagne that is so good to grape vines? It all begins with the Paris Basin and the geological history of this feature. After looking online for a long time, I found this image that is truly a picture worth 1,000 words. On the left side is a color-coded timeline, on the top is the view of the Paris Basin from space and on the bottom is a cross section of the Paris Basin.²
To understand what is so special about the Paris Basin, we'll have to travel back in time. The area around the Ile de France or the Parisian Basin was once an inland sea that covered most of France until about 70 million years ago. The sea was teeming with various marine organisms, such as sea urchins, sponges, starfish and in particular belemnites (an extinct relative to the cuttlefish/squid).
Marine sedimentation in the Paris Basin began in the Permian(oldest) and continued into the Tertiary(newest). During that time, more than 3000 meters of sedimentary rocks acummulated in the basin center. About 30 million years ago an earthquake at the center of the basin caused the dried up seabed to break up and rise some 60 meters. The broken up subsoil contained huge deposits of the sea creatures fossilized remains that varied in depth between 100 to 300 meters.

      Map is from Geocaching, Le Champagne et la craie.²
The vineyards of Champagne grew on this bedrock where gravels, clays, silts, pebbles, meet the marl, clay limestone, sandstone, and conglomerates. The main part of the vineyards follows the 125 kms irregular line of the coast called Falaise de l’Ile-de-France from l’Aisne, to the northwest of Rheims to the Seine in Nogent.
The Chalk hills in Champagne are capped by soft, Paleocene sands and muds, which are locally lignitic. These sediments have been washed down the chalk slope, as far as the base of the Belemnite zone.¹ Champagnes chalk soils can be sub-divided into two biozones based on the range of fossil material. The uppermost zone is ‘belemnite’ (an extinct relative to the cuttlefish/squid) dating from the Tertiary period and the lower zone ‘micraster’ (sea urchin/starfish) from the Cretaceous period.
Coming full circle to the beginning of this blog, it was this difference in soil composition that made the early winegrowers decide what type of soils their grape vines grew better on. But, geology is only one of many factors in wine quality and, in most cases, the influence of the bedrock is only indirect. There are other factors to take into account, especially the viticultural methods, that probably are the most important control.
References:
1. Jennifer M. Hugget, Geology and wine: a review, Proceedings of the Geologists’ Association, 117, June 2005, p. 239–247.
2. Mangenot, Xavier & Gasparrini, Marta & Gerdes, Axel & Bonifacie, Magali & Rouchon, Virgile. (2018). An emerging thermo-chronometer for carbonate bearing rocks: Δ47/U-Pb. Geology. in press. 10.1130/G45196.1.
3. Geocaching, Le Champagne et la craie.
4. Geotourism, Paris Basin - The Geological Foundation for Petroleum, Culture and Wine. 4. The World of Fine Wine, Wine and the Mists of the Distant Past: Geological Time Explained, Issue 48, 2015.