The scenic landscape of Austria has been significantly shaped by the main geological units: the highlands of the Waldviertel and Mühlviertel regions form part of the Bohemian Massif in the north, followed by the undulating hilly Alpine Foreland with great valleys and basins in the east, and finally the mountainous Alps, which extend for over 500 km lengthwise across the country.
The Eastern Alps are part of a large mountain arc that extends from the Riviera to Vienna and form, seen from a geological perspective, a crumpled zone where the Adriatic and the Eurasian Plates encounter each other. The continuation of the Alps occurs underneath the basins in the east of the country, covered by sediments of up to 5000 m in thickness, and reemerges in the Carpathian and Dinaride mountain ranges. The large-scale structures are the result of plate-tectonic developments, which have brought about formation of rocks that are now hundreds of millions of years old, alteration of the distribution of land and water, displacement and breakup of continents, separation and isolation of seas as well as the uplift and subsequent erosion of mountains.
However, rocks and the course of tectonic boundaries also have a direct impact on the landscape on the smaller scale. Soft, easilyweathered rock tends to give rise to gentle landforms while rugged mountain shapes and steep cliffs are usually related to hard and brittle rock types. Valleys often follow the trend of tectonic faults. Due to rapid erosion in areas with soft bedrock canyons and almost vertical undercut, slopes can form along rivers. Conversely, where there is underlying hard bedrock under suitable climatic conditions and with small height differences, undulating and gently- rolling landscapes may be formed.The great climatic fluctuations of the Quaternary Period proved essential for landscape development in the Alps in more recent geologic times, with the effects of at least four glaciations or cold phases of the so-called Ice Age being present. The abrading force of the great glaciers and frost shattering caused large quantities of rock to be eroded. Due to alternating erosion and deposition by the glacial meltwaters, gravel terraces formed and as a result of the drift of rock dust from the barren mountains, loess was formed in the foreland areas.
In addition to composition of the rocks, tectonic boundaries, uplift and subsidence of the land surface and climate development, factors such as vegetation and human interventions also contribute to the character of the landscape.
Since the major rock units basically travers Austria in a lengthwise fashion, while the winegrowing regions trace an arc in the east of the country, these consequently include manifestations of almost all the main geological units. This is why our wine landscapes are so varied and interesting!
Rocks can have very different cohesion properties, thus the first rough division is accordingly made between consolidated and unconsolidated rocks. About seventy per cent of our domestic vineyards are located on unconsolidated bedrock, with about thirty per cent positioned upon soils that have been derived from solid bedrock.
Types of consolidated rock relevant to this case belong to the following major geologic units in Austria:
- The Moldanubian and Moravian Superunits occurring in the area of the Bohemian Massif consist of crystalline rocks of Proterozoic and Palaeozoic age
- The Helvetic Superunit and klippes of the Waschberg Zone, formed from rock deposits (sedimentary rocks) of Mesozoic and early Cenozoic age
- The Penninic Superunit composed of rocks derived from an ocean that existed in Mesozoic and early Cenozoic time. On the northern edge of the Eastern Alps lies the Penninic Flysch Zone. Similar rocks are found in altered (metamor- phosed) form in the region of the Central Eastern Alps where they are exposed in so-called tectonic windows below the Austroalpine Superunit
- The Austroalpine Superunit, formed from rock deposits of late Palaeozoic, Mesozoic and early Cenozoic age in the Northern Calcareous Alps and the Gosau Group, and consists of altered rocks (metamorphic rocks) and rock deposits (sedimentary rocks) of Proterozoic, Palaeozoic and Mesozoic age in the Central Eastern Alps
The unconsolidated rocks belong to the following geological units:
- Molasse Zone in the Alpine Foreland, formed from rock deposits of early and late Cenozoic age (Palaeogene and Neogene) up until about 7 million years ago
- Inner Alpine basins such as the Vienna Basin, Styrian Basin and the Pannonian Basin, composed of rock deposits of the Cenozoic (Neogene) up until about 2.6 million years ago
- Deposits of the most recent geological period, the Quaternary, which are concentrated in the Molasse Zone and in the basins, but also overlap onto areas of consolidated rocks
Within the unconsolidated rock domains, there are also occurrences of consolidated rocks:
- Consolidated sands, gravels and rock debris forming sand-stones and conglomerate or breccia
- Leitha limestone
- Volcanic rocks within the Styrian Basin
The limits of the large units of time are:
- Proterozoic: older than 541 million years
- Palaeozoic: 541 - 253 million years
- Mesozoic: 253 - 66 million years
- Cenozoic: 66 million years – present time, the Neogene / Quaternary boundary is placed at 2.6 million years ago, the Pleistocene and Holocene boundary is placed at 10,000 years before the present.