Microscopic deformation structures in archaeological contexts

Evidence of deformation at the microscopic level in archaeological contexts is rather rare. To address the problem of identification of deformation structures, a series of experimental floors were prepared and studied by micromorphological analysis. Ethnographic samples of constructed floors and mud bricks were also used. Constructed floors and mud bricks from prehistoric sites were then reanalyzed in light of the experimental findings and compared with the ethnographic ones. Small-scale debris and mud flows from archaeological contexts were also analyzed to identify microscopic deformation structures that could be compared with the rich available literature on such sediments. Microscopic deformation structures were identified in all types of samples: they included rotational and planar features, fold structures, boudins, and other squeezed features, shear planes, and water-escape features. It appears that in some cases there is no clear difference between microscopic deformation features that develop in either geogenic or anthropogenic deposits. Furthermore, there is some overlap between deformation features produced by trampling and those in the formation of mud constructions that needs to be resolved with more experimental work. Nevertheless, trampling of water-saturated sediment produces deformation features that, for the most part, are the result of compression and not shearing.