Archaeology and Geomagnetism: Investigating the Earth's Magnetic Field in Italy during the Neolithic Period. New Data from the Portonovo Archaeological Site (Marche, Italy)

English Abstract:

Archaeomagnetic data from ancient baked clays is a precious source of information about the past variations of the Earth's magnetic field. Thanks to archaeomagnetic records from well dated archaeological artefacts it is possible to reconstruct the geomagnetic field variations in the past and better understand its behaviour. On the other hand, once a detailed secular variation path is established for a certain area, reliable archaeomagnetic dating is possible. In order to enrich the Italian reference database and extend it back in time, we present here the results of an archaeomagnetic study carried out on three Neolithic ovens excavated at the archaeological site of Portonovo (Marche, Italy). The discovered structures are a rare example of well preserved domed ovens from the Early Neolithic period, dated based on archaeological information and radiocarbon dating. Standard thermal demagnetization procedures were used to determine the archaeomagnetic direction registered by each oven during its last firing and their archaeointensity was determined with the multi-specimen procedure (MSP-DSC). Both directional and intensity results are of high quality and they clearly show an intensity low during the Neolithic period. These new results, that are the first full geomagnetic field vector data available for this period in Italy, have been compared with other contemporaneous data from Europe and with global geomagnetic field models. Independent archaeomagnetic dating of the three ovens has been also performed using the SCHA.DIF.8k model. The obtained results are in excellent agreement with the radiocarbon dates, confirming that all ovens belong to the Neolithic period and were almost contemporaneously used. The new results importantly enrich our knowledge of the geomagnetic field during the Neolithic period that is poorly covered by data, not only in Italy but in the whole Europe and show that archaeomagnetic dating can provide accurate results even for prehistoric periods.