Arqueomagnetismo en “fumiers” recreados experimentalmente¿son registros fiables del campo magnético terrestre?

Resumo

It has been proposed that burnt sediments from Holocene cave-pen sites (cf. fumiers), are suitable recorders of the Earth ́s magnetic field direction in the past. These are burnt, well-dated and remarkably old materials (from the Neolithic). Howe- ver, the taphonomic processes affecting their archaeomagnetic record are diverse and have not been studied yet. In order to evaluate the impact of these processes, samples from experimentally recreated fumiers under controlled conditions (Vergès et al. 2016) were collected for directional and magnetic properties analyses. The main magnetization carrier is pseudo-single domain (PSD) magnetite with high but variable contributions of superparamagnetic grains depending on facies. Anisotropy of magnetic susceptibility (AMS) values are significantly low. However, the stereoplot analysis indicated some control in the alignment of the principal susceptibility axes, suggesting the influence of some factor in the formation of the fabric. The directional behaviour varies by facies but is characterized by intense and stable normal polarity samples.