More than primary rock and loess
June 3, 2014 - Steep slopes, valleys, rolling hills, terraces and specific sites of the Austrian wine regions are features that belong to the visible charm of our country’s landscapes. Hidden beneath the soils the rocks usually are not visible, but they are of great importance to the winemakers because they influence significantly the choice of grape variety and vineyard management. Dr. Maria Heinrich, geologist with the Geological Survey of Austria, has been working on the geology of the domestic wine regions for many years and has summarized the most important points in the new chapter on Geology of the ÖWM training manual.
The rocks that form the source material for soils, but also our present-day landscape and climate, are products of the development of the history of the Earth. Geological research is focused on these aspects and the practical implications arising from these studies have raised the general awareness of geology, also within the wine community. The rocks determine how deep the roots of the vine can penetrate to find water, whether the soil is stony, sandy or loamy, whether the colour tends to be lighter or darker, whether it has the capacity to retain heat, air and water, whether clay minerals are present that facilitate the exchange of inorganic nutrients and whether the soil is inherently carbonate or lime-free.
Vineyards instead of ocean bays
The varying hardness of rocks, the course of tectonic boundaries as well as large-scale uplift and subsidence processes affect the landscape of the wine growing areas and, due to their respective altitude, orientation and slope, influence also the relief of the soils and consequently, the local climate of the vineyards. These factors and Austria’s location within the northern wine-growing belt of the Earth are the result of plate tectonic motion of the Earth’s crust, and related changes in the position of oceans and continents. This motion has also given rise to mountain ranges and is the reason why the lowlands in the east of the country are no longer occupied by seas but instead are areas displaying diverse cultural landscapes.
Since the major rock units essentially traverse Austria lengthwise, while the wine-growing regions trace an arc in the east of the country, the latter consequently include occurrences of almost all the main geological units. This is why our wine landscapes are so varied, unique and interesting!
Unconsolidated or consolidated, that is the question
About 70 percent of our domestic vineyards are located upon unconsolidated rock substrates while approximately 30 percent are sited upon soils that developed from consolidated rocks. Both groups comprise very different rocks, which are separated on the basis of the structure and composition of their chemical and mineralogical constituents. Included among the consolidated rocks are acidic granites, gneisses, schists and quartzites, basic amphibolites, serpentinites and basalts, and also marbles and limestone, conglomerates, sandstones and volcanic tuffs. Predominant among the unconsolidated rocks are first and foremost calcareous loess, sandy gravels and rock debris derived from river terraces as well as sandy and clayey silts, the remnants of a large lake landscape that formed in the wake of the retreat of the sea about 11 million years ago.
The full chapter „Wine & Geology“ may be found under the ÖWM training manuals on pages 10-15.