Despite its broad extent, at first glance an exploration of the geology of Touraine promises to be a lot less complicated than it is for some (if not all) of the other regions of the Loire Valley. Unlike the igneous and metamorphic complexity of the Nantais vineyards, superficially little more than a random geological jigsaw, the misunderstood metamorphic and limestone twins of L’Anjou Noir and L’Anjou Blanc, the former loved, the latter mostly forgotten, and the multi-multi-multi-layered limestones, marls, fossils and flints of the Central Vineyards, the geology of this broad region is surprisingly uniform, and – at least superficially – rather more straightforward.
This is because Touraine geology is all about limestone. And, truth be told, largely one type of limestone, and not much else. Of course, the limestone is partnered by those geological features which accompany it, wherever limestone goes, namely flint and clay. While on top of it all lies the superficial detritus, the pebbles, gravels, sands and silts strewn on either side of the region’s great rivers. Grasp that, and you are already a long way towards understanding Touraine terroir.
In the case of the Loire and the Vienne these alluvial deposits fill broad and shallow valleys, so wide in some places it is several kilometres from one sloping clay-and-limestone valley wall to the other. And it is on these slopes or the edge of the plateau at the top, where the limestone comes close to the surface, that the best wines are often made. A very good example of this is illustrated below.
I took the above photograph when standing in La Croix Boissée, a highly regarded vineyard in the Chinon appellation situated on the limestone slopes on the right bank of the Vienne. The parcel belongs to Bernard and Matthieu Baudry; the vines run down and then out across the valley floor. Through the trees at the foot of the slope runs a small stream, Le Canal, while the Vienne itself is hiding among the trees in the far distance. The opposite wall of the valley, 2.6 kilometres away, upon which sits Clos de la Dioterie, the top vineyard in the Charles Joguet portfolio, is just below the horizon.
None of the vineyards on the alluvial soils of the valley floor have any renown, with perhaps just one or two exceptions. On the slopes, however, it is a different story. The association between the clay and limestone soils and the quality of the wine is undeniable.Please log in to continue reading: