Rock magnetism as a tool for investigating the use of archaeological artefacts from baked clay

<p>Even though multidisciplinary approaches applied to the investigation of archaeological findings are widely used, the use of rock magnetic properties is still poorly exploited in the determination of the use of ancient artefacts. In this study, we present the results of a combined archaeological, morphological and magnetic analyses applied on the ring-shape clay artefacts found at the archaeological site of Villa del Foro, in Northern Italy. The materials studied are dated between the sixth and the first half of fifth century BC and are found in large quantities in different trenches of the archaeological excavation. To investigate their thermal history and to exploit their possible use as kiln supports, cooking stands, or loom weights, we have investigated their natural remanent magnetization (NRM) and the magnetic mineralogy changes occurred during laboratory heating. Magnetic analysis used for the determination of the firing temperatures show thermal stability up to 500-600 <sup>o </sup>C, while further laboratory heating at 700 <sup>o </sup>C introduces magnetic alteration. Thermal demagnetization of the samples generally shows a strong and stable thermal remanent magnetization. In few cases, a clear secondary component is present, suggesting partial re-heating or displacement at temperatures ranging from 200 <sup>o</sup>C to 450 °C. Such secondary magnetic component can be indicative of a secondary heating or of a displacement of the rings from their initial firing position while still hot. Even though the studied rings belong to casually different morphological typologies, no connection among type and magnetic behavior was observed, suggesting that the ring’s morphology does not define neither their production conditions nor the final use of the artefacts. The estimated firing temperatures of around 600-700 <sup>o</sup>C are compatible with the heating of the rings during their manufacture rather than related to cooking activities. In combination with the archaeological evidence and the morphological analysis it is thus suggested that the rings were used as weight looms and baked only during their production procedures. Such a pilot study can be used as reference for the identification of similar objects found in Italy and Europe during the Iron Age and confirms the great potential of rock magnetic analysis in the investigation of the technology and use of ancient baked clays.</p>

Paleomagnetic and rock magnetic investigation in marine sediments, Nankai Trough, offshore Cape Muroto

<p><span>The Nankai Trough is an accretionary complex which extends over several thousands of kilometers along the Japanese Pacific coast. Many ocean scientific drilling expeditions have taken place in this zone to better understand the mechanisms of big earthquakes and generation of devastating tsunamis. Offshore Cape Muroto, Shikoku Island, is one of investigated zones. A recent International Ocean Discovery Program (IODP) expedition (IODP Expedition 370) in the area has focused on the temperature limit of life in deep subseafloor sediments. Here we present paleomagnetic and rock magnetic preliminary results on two neighboring sites in this zone drilled during two former Ocean Drilling Program (ODP) legs: Site 808 of ODP Leg 131 and Site 1174 of ODP Leg 190. At all sites, shipboard magnetostratigraphy was challenging because of a strong diagenetic alteration of the magnetic mineral assemblages. Four main downcore magnetic zones, characterized by specific magnetic properties and mineralogy, are identified. At Site 808, catagenesis of the organic matter has been proposed to explain the downcore rock magnetic properties. This explanation however could not stand for Site 1174. We present here a first attempt of a comparative paleomagnetic and rock magnetic study in high temperature marine sediments, off Cape Muroto. </span></p>