The higher the place of sedimentation, the thinner the layer of the sedimented material is. At the Kaiserstuhl the thickness of the loess layer varies between 10 and 40 metres. There are, however, also areas in the southwest where no loess has been deposited. The Northern Limestone Alps are considered the main source of the Kaiserstuhl loess. A rust-coloured band occurs at irregular intervals. It developed as a new material and did not arrive regularly but in phases of different intensities. In a phase of weak sedimentation the material on top weathered - and the calcium carbonate was washed out. It then precipitated further down and formed a particular type of soil horizon, which contains concretions of calcium carbonate.