Zur Entstehung von Gehniveaus in sandig-lehmigen Ablagerungen : Experimente und archäologische Befunde

The effects of human trampling on sandy-loamy surfaces are presented, based on two experimental series. The scientific analysis of the experiments allows statements on type, intensity and tendency of the changes of microstructure in humid and dry sediments. Micromorphological analyses prove that the trampling phenomena which can be detected microscopically are concentrated in zones near the surface or up to a depth of 3 cm at the most. The microstructural changes in humid sediments are more significant and generally reach somewhat deeper. In dry conditions the effects of trampling are limited to a few millimetres just below the activity surface, while compared to humid sediments, a stronger fragmentation of the components becomes apparent. A field test on the intensively trodden excavation site of Basel-Gasfabrik over a six week period resulted in an accumulation of 5 to 8 cm of reworked soil material brought in by trampling. The second part of the paper deals with well preserved archaeological occupation surfaces, comparing their characteristics with the results obtained from the experimental series. The processes defined by Gé et al. (1993), that have an effect on an activity surface, such as accumulation, depletion, transformation and redistribution, were qualified for each archaeological feature. Experiments, archaeological evidence and literature research prove that the microscopically detectable characteristics of trampling can manifest themselves in microstructure, in the occurence of horizontal cracks and horizontally oriented components, in crust formation, in deformation and reorganisation phenomena and in the results of mechanical influences (rounding, crushing or destruction of components). In this, our observations correspond with the results of former analyses by Courty et al. (1994). In addition, with the evidence of interlaced silty intercalations they provide a little known microstructural characteristic which also indicates trampling. Betr. das Ausgrabungsgelände Basel-Gasfabrik