Resumen de A taphonomic study of Ochre demostrates post-depositional color transformations
The predoninance of red ochre over other clors in Middle Stone Age deposits has led archaeologists to suggest that this color was chosen for symbolic reasons. While this may have been the case, replication studies imply that the dominance of red ochre in archaeological deposits can result from either anthropogenic or post-depositional activities. Yellow, brown and orange hydrated iron oxides can be transformed from yellow or brown to red, or shades of red, through heat in simple camp fires. Ochre processing areas and variously colored ochre nodules found at Sibudu Cave, South Africa, confirm the presence of both hydrated and dehydroxylated forms of iron oxide. Replications demostrate that yellow ochre can transform to red or shades of red when it is buried in sand under a fire. Temperatures of 300 to 400 degrees C can routinely be obtained 5 cm below a small camp fire and temperatures of close to 300 degrees C can even be achieved 10 cm below the centre of a fire. Such conditions are ideal for dehydroxylating iron oxides and transforming their colors. In the past, the transformation may sometimes have been deliberate, but on ther occasions ochre nodules or ochre residues present on artefacts may have been heated serendipitously throungh unintentional proximity to heat; thus fires lit above ancestral camp sites can cause post-depositional change to the colloids or minerals thousands of years after they were used at a site.
