Magnetic alteration of Soils by Late Holocene Hunter–Gatherer Groups (Tierra del Fuego, South America)

The present work aims to analyse the magnetic signature from the Late Holocene open-air archaeological deposits of hunter–gatherer ephemeral occupations. For this purpose, two profiles were sampled at the Marazzi 2 site in the north-western Isla Grande de Tierra del Fuego, Chile, in order to carry out studies of magnetic susceptibility, hysteresis cycles, back-field remanent magnetization, isothermal remanent magnetization and thermal variation of magnetic susceptibility at high and low temperature. Despite short-term occupations, the P1 profile shows a magnetic peak at a depth of ~30–70 cm due to magnetite, probably formed by anthropogenic activity related to combustion. The P2 profile instead yields an anomalous peak of coercivity (at a depth of 20–40 cm), which could also be anthropogenic, due to the presence of finely dispersed ancient ‘red ochre’. The red ochre is proposed to form anthropogenic thermal alteration of goethite associated with volcanic ash, the remnants of which were found in thin sections from the P2 subsoil.