A book entitled “Stein & Wein – Die Geologie der Schweizer Weingebiete” (Stone and wine – the geology of the Swiss wine regions) is currently in the making under the leadership of the Swiss Geotechnical Commission, which has its head office at ETH Zurich. Rainer Kündig and Willi Finger, both of whom are scientists, wine lovers and co-editors of this “wine geology”, report on a special project on the interface between intuition and science.
The area around the municipality of Fully in Lower Valais. The vineyards are situated beneath folded, crystalline rock formations that are rich in limestone. Erosion has led to the creation of alluvial fans in the valleys on which wine is now cultivated.
What is the secret of what is referred to as mineral wine, such as a “Vin du glacier”, a glacier wine from Switzerland’s Valais region, or the “Tracce di Sassi”, a Merlot from Ticino that bears traces of sedimentary rock? Can geological flavours from the ground beneath a vineyard give the wine a spicy mineral note? In short, is it possible to taste the stone beneath the wine? A subjective field of experimentation
There is divided opinion concerning the issue of minerals and wine. According to Rainer Kündig from the Swiss Geotechnical Commission, there are two distinct camps of “believers”. “I have talked to winegrowers who are convinced that their wines have aroma components that stem from minerals. But there are others who think that any talk of a taste of stone in the wine is rubbish.” The earth scientists have thus tackled a controversial topic that can even be regarded as a subjective field of experimentation “on the interface between unambiguous geological links and suppositions, between what we feel intuitively and what we are taught, between intuition and hard evidence”.
The project with the modest title “Stein und Wein” (Stone and wine) has the ambitious aim of “getting to the bottom of geology as a factor in the Swiss winegrowing regions”. Together with a team of 40 authors who are “wine lovers with a background in geology and wine experts with an interest in geology” from across Switzerland, Kündig is working on a comprehensive book that examines and classifies the wine regions by geological subsoil rather than cantonal boundaries.
Willi Finger, another geologist with an interest in wine and member of the editorial team, uses the following example to explain the approach followed by their «wine geology» of Switzerland: «The fundamental question is whether rock and deposits of mineral elements in the subsoil – limestone, gneiss and gypsum or calcium, silicon, sulphur and iron respectively – have an effect on the vine and on the wine. In order to find an answer, we carried out a geological and sensory examination of Swiss wine regions with unusual rock bases as well as their produce.”
One example is the vineyard in Sargans at the foot of Mount Gonzen. This is the site of the largest iron and manganese deposits in Switzerland, estimated at 5.5 million metric tons. An ambitious winegrower is cultivating the “quite challenging” Pinot noir grape directly adjacent to the iron mine, which was closed down in 1969. Willi Finger tells us that while no clear note of iron or manganese was detected during blind tasting, there was agreement on the high quality of the wines produced in this region.
Is this due to the special geological make-up at the base of the Gonzen mountain? The two scientists from ETH Zurich assume this to be the case. “There are many factors which indicate that the rock base influences the growth of a vine”, says Rainer Kündig. For example, vines absorb the rock’s mineral elements dissolved in the groundwater through their roots. “In fact the earth – as a substrate for the plant – is a product of the weathering of bedrock, combined with biological and geomorphologic processes.”
Some of the vineyards in Zurich are rooted in molasses sediments – debris deposits that were washed from the Alps down into the foothills around 30 million years ago. Later, during the Ice Ages, lots of moraine material from the drainage basin of the Linth Glacier was deposited on top of those.
“However, it would be an exaggeration to claim that you can taste these ice age remnants in the wine”, says Kündig. “Taste is always a subjective experience.» Willi Finger adds: «Our main objective with the book we are writing is to provide geological expertise regarding one of humanity’s oldest cultural assets.”