Loess – rock and soil at the same time
The soil is usually the weathering product of the underlying rock. This is very different with the terraces of Gedersdorf. It is a sediment deposited by the wind, which has been standardized by working of top and bottom soil.
For a long time, geologists discussed the formation of this sediment. Because of the well-known loess areas in China, there was the assumption that it came from Gobi as well. This is where the anecdote by geographer and China researcher Ferdinand von Richthofen (1833-1905) fits in well: on his birthday, an album of his creative fields was to be given to him. Since the University of Vienna found no picture of the China Loess terraces, they handed him instead one of the Gedersdorf terraces..
The origin from gobi could have explained the uniform composition of grains of 0,02 to 0,05 mm in diameter. But a shipment over this enormous distance would be very unlikely? Meanwhile, there is a more conclusive explanation:
Our loess is a formation of the ice ages. The last ice age came to an end about 12,000 years ago. After the retreat of the glaciers large areas without vegetation remained and there were strong differences in the air temperature. The ice-free areas warmed up more than the icy areas and this caused strong and steady storms. The frost bursting and the inner friction of stone produced small clastic grains. These grains could be blown by the wind. It must have been sandstorms in the still vegetation less land. The dust was then deposited in the lee side of elevations of the land. The necessary elevation was provided by the Hollenburg-Karlstetten geological formation, consisting of psephit in Gedersdorf. Loess therefor was deposited by the wind – an “aeolian sediment” – and it comes from ancient river valleys.
The chemical analysis shows mainly quartz followed by calcite and mica. The content of lime has significant viticultural effects. Loess has little humus, so it is light. Iron oxide give him a tint of yellow.
The loess areas were heavily populated in the Stone Age. During the loess mining in Krems around 1900 – the material was used for dam construction on the Danube – more than 20,000 stone tools were found.
The grains of the loess are glued slightly together by lime – previously dissolved by water – and combine it very compactly, therefore it does not behave like sand in dunes. This property means that cellars without vaults and terraces without stone walls can be built. Our cellar is built in loess. There are two vaults stacked and above them there is the vineyard. This is a total of 10 meters loess, making it one of the most powerful loess deposits in Europe.
To loess vergin soil the soil scientists say Rigolboden. Through rigolen (= deep plowing) and also through the construction of terraces, the undoubtedly formerly existing humus layer was mineralized and so degraded. This was promoted by the high air content. The soil is uniformly yellow from above.