Archaeomagnetic Tools Applied to the Study of Middle Palaeolithic Hearths: The Level R (ca. 60 ka BP) at Abric Romaní (NE Iberian Peninsula)

Identifier:  imarina:9452268

Handle: https://hdl.handle.net/20.500.11797/imarina9452268

Authors:  del Rio, Judit; Palencia-Ortas, Alicia; Gomez-Paccard, Miriam; Carrancho, Angel; Saladie, Palmira; Chacon, M Gema; Carbonell, Eudald; Vallverdu, Josep

Abstract:
Due to its long occupation throughout the Middle Palaeolithic and the abundance of its pyrotechnological evidence, the Abric Roman & iacute; rockshelter (Capellades, Barcelona) provides an ideal setting for studying Neanderthal fire use. We conducted an archaeomagnetic study of four hearths from Level R (ca. 60 ky BP). Rock magnetism experiments, including hysteresis loops, and backfield, isothermal remanent magnetisation acquisition and thermo-magnetic curves, were conducted on three specimens per hearth to investigate their magnetic mineralogy. To explore the raw material's ability to become magnetised, we performed a laboratory-induced partial thermo-remanent magnetisation acquisition in a 50 mu T field at various increasing temperatures. Our results indicate that the material is predominantly diamagnetic, but contains a small proportion of low coercivity magnetic minerals, likely magnetite. A total of 106 oriented specimens underwent progressive thermal demagnetisation up to 580 degrees C. Directional results at the specimen level show either a single component or two: one between 250 and 420 degrees C and another between 300 and 550 degrees C. Three out of the four hearths yielded normal-polarity archaeomagnetic directions, within the range of secular variation expected for their estimated age; the poor quality of the data prevented any analysis of the remaining structure. These findings suggest that, despite the hearths' low content in ferromagnetic minerals, they are able to acquire a thermal or thermochemical-remanent magnetisation, accurately recording the Earth's magnetic field though their high-temperature component. The low-temperature component may reflect a subsequent thermo-chemical or chemical alteration that partially remagnetised the original direction.