Trampled under foot: A quartz and chert human trampling experiment at the Cova del Parco rock shelter, Spain

An assemblage of 500 (385 quartz and 115 chert) experimentally knapped artefacts, underwent human trampling over the course of two weeks by a team of 10-12 excavators wearing soft-soled shoes used while excavating in the rock shelter. Two zones of trampling were used: Zone 1, a high artefact density, low trampling intensity, and lower soil compaction and rockiness; and Zone 2, a low artefact density, high trampling intensity, higher soil compaction and rockiness. The primary questions were to understand the difference in fracture rates and types between the chert and quartz, and the difference between the zones of artefact density, trampling intensity, and soil density. The results have shown that significantly more quartz fractured and were damaged compared to chert, and for both materials there was significantly more breakage in the zone with the higher trampling intensity and higher soil compaction and rockiness. There was no discerned association between the original artefacts' size or weight and the occurrence of breakage of the quartz and chert artefacts, except for a very weak association for narrower and thinner quartz artefacts being more likely to break. Overall, there was relatively little horizontal or vertical movement of the artefacts over the two weeks, with the largest size ranges moving the most, but with no significant difference in the movement of artefacts amongst the smaller size ranges.