The Alps are a young orogen, in which the relatively simple geological relationship between basement and platform that exists in the area north of the Alps has been overprinted and complicated by orogenic processes. The formation of the Alps happened in tectonic domains, but within which basement and platform can be distinguished, which either jointly or separately, are built of separate nappes. The nappes outcropping in the German Alps invariably contain platform units of folded, unmetamorphosed sedimentary rocks, mainly of Mesozoic age, which were deposited almost exclusively in a marine environment. They are associated with three of the four domains of the Alps.