Montalcino: Geology & Soil
Jan Erbach of the Pian dell’Orino estate describes Montalcino’s underlying geology as ‘complex because it was formed by the Sardinian and Corsican geological micro-plates (the latter being part of the African plate) drifting north-east into what is now mainland Europe, which of course has its own geological plate. This collision created the Appennines which came out of the sea 140 million years ago and are still rising. The African plate went under the Eurasian plate and created the Alps. The Montalcino zone’s topography and soils have several very varied influences too. The soils may have come from volcanic activity (Mount Amiata which left a sea of clay in Montalcino), from warm seas full of life which produce nutrient-rich soils, or from colder and life-poor ones which produce heavier soils with fewer nutrients [eg. galestro]. I have four different soil types in one of my smallest vineyards – bright clay, dark clay, dark stones, and light sand – and I am not alone. If I farm this vineyard as one homogeneous whole I’ll make a mish-mash of a wine with only moderate qualitative potential. However, by planting different Sangiovese clones on different rootstocks in each of the different soils, and then pruning, tending and picking the different sub-parcels of vines in subtly different ways, I can make maybe three really good top-priced wines and one really good lesser-priced wine. If every wine-grower in Montalcino had access to more information about what exactly their vine roots are digging into they’d be able to make better-informed choices when matching rootstocks and Sangiovese clones to certain soils, be they galestro or alberese or Pliocene clays. This would at least give each vine a much better, more qualitatively productive foundation, or foothold, in the Montalcino terroir.’
Kerin O’Keefe (11 2006 p.76) says in ‘Montalcino was formed in different geological eras. Younger soils, comprising alluvial deposits from the Quaternary Epoch and clay from marine deposits during the Pliocene Epoch, dominate in the southern lowlands, while further uphill the terrain is mainly clay enriched with calcareous fossil material (Miocene-Oligocene). In the upper part of the territory, the soil is moderately stony, mixed with sand and rich in lime. The well-draining soil here is very old (Cretaceous-Eocene-Jurassic) and can restrain the youthful exuberance of productive grapevines…a prudent clause in the original  production code did specify that vineyards had to be “on land of Eocene origin,” which effectively limited Brunello production to the higher altitudes and most suitable soils. This was later revised, however, to include land up to the Pliocene period, clearing the way for cultivation throughout the entire denomination.’
Soil pH: Enzo Tiezzi told me on 09th April 2015 that ‘Montalcino has generally alkaline (‘sub-acido’) soils. This is what gives the Sangiovese wines their ‘salinità or savoury-salty aspect’.