Our Soils
Three main soil types have evolved in the Swartland from the parent materials that dominate the area, these are shale/schist-, granite- and iron-based soils; each with very different characteristics and therefore creating unique growing conditions.
Granite Soils
These deep, sandy soils are found close to, or on the granite outcrops of the Paardeberg Mountain. This zone was invaded several times by the sea due to land recession, uplifting, and changing sea levels. The soils are generally duplex in character, consisting of a very deep layer of course, bleached sand on top of a thick layer of wet or gleyed clay. The sandy topsoil is extremely well drained, but the thick, dense layer of clay, which often lies meters below the surface, acts as a slow-release sponge for the vines’ deeper roots over the summer. Wines from these soils tend to be exceptionally pure with a floral and spicy granitic perfume and nervy acidity.
Schist Soils
These soils on the Riebeek Kasteel and Porcelain mountains, on the eastern side of the Swartland, are based on Malmesbury shale. These are sedimentary formations but share similar properties to the metamorphic schists of Cote Rôtie, Faugeres and Priorat. These are mostly found on hillsides and are relatively shallow, rocky and well drained. The vines are never in a situation where they can sit back and enjoy life; they are forced to push their roots down in search of water. Fortunately, shale-based soils generally have a good clay content, and this means there is generally moisture available between the bedding planes for the vines’ deeper roots. Wines produced from these soils tend to be dark fruited and well-structured from the open canopies and small, thick berried grapes.
Iron Soils
Vines grown in gravel & iron based soils struggle to grow, as there is never excess water about (resulting in extremely low yields) but they are protected from serious stress by the soil’s water retention capacity. This helps the vines towards the end of summer, when it is very dry in the Swartland, allowing them time to build complexity and tannin in the grapes. Wines produced from these soils tend to be deep in colour and are very concentrated. They easily show reduction, while being structured and grippy on the palate. They bring loads of mid-palate to any blend.
Quartz Soils
Quartz is an extremely hard rock that breaks down much more slowly than the surrounding schist and through rain and gravity over time the quartz rocks have slowly moved down to the lower slopes of the Kasteelberg mountain where we now find pockets of very deep soils with a layer of white quartz rocks on the surface. Vines planted here are able to build deep root systems and benefit from a good clay content in the soils which produces wines of beautiful mid-palate texture combined with freshness. The white quartz rocks on the surface reflect light back up into the canopy of the vines and this additional light gives the fruit a beautiful golden hue and brings aromatics of stone fruit and yellow citrus.
Swartland Geology
Although viticulture in the Western Cape is relatively young, the geology is quite old. Our vines are planted on the most ancient viticultural soils on earth, and we need to go back half a billion years to see how the landscape evolved.
Through tectonic collisions and of the continents some millions of years ago, the shale based soils found in the Malmesbury area were infused by Magma, from deep within the earth. It rose along the continental fault line into the thick shale deposit, and slowly cooled and crystalised into the granite rocks and hills we see exposed today.
Later, because of the continents separating, it caused the surface to subside and become covered from the north by very deep deposits of Sandstone, called the Cape Supergroup.
What is left today are sandstone remnants like Kasteelberg and Piketberg (1000-1300 m altitude), resting on granitic and shale foothills and associated with exposed graniteoutcrops such as the Paardeberg (500-700 m altitude) and ranges of shale based hills like Porseleinberg and the Malmesbury hills (200-400 m altitude), surrounded by undulating Malmesbury shale landscapes.
As human beings, we are given such a short time on this planet to work with the land. It is humbling and exciting to keep this ancient history in mind, and as our vineyards grow in soils derived from all this tectonic activity, it is fascinating to think of the links between how the earth evolved and how wines grown in different sites taste.
These humbling thoughts are the fundamental reason for our natural winegrowing and winemaking approach as we strive to bottle wines that reflect the Swartland.
MULLINEUX WINERY
