14,437 research outputs found
Magnetic measurements as indicator of the equivalent firing temperature of ancient baked clays: New results, limits and cautions
No full textWe present new experimental results on the variation of the magnetic properties of baked clays as afunction of the temperature reached during laboratory treatments. Such experiments, including contin-uous monitoring of the magnetic susceptibility and magnetic moment versus temperature, were appliedto a set of natural clays experimentally heated in the laboratory at 200◦C, 400◦C and 600◦C as well asto archaeological baked clays collected from two archaeological sites in Northern Italy (Santhià and Car-bonara Scrivia). The aim of this study is to investigate the reliability of the magnetic properties to identifythe equivalent firing temperatures of ancient baked clay artefacts based on the reversible behavior ofthermomagnetic diagrams. The results obtained indicate that the magnetic properties do not alwayssucceed in estimating the firing temperature of the baked clays, mainly when clays have been heatedonly once and at relatively low temperatures, e.g. less than 300–400◦C. On the contrary, magnetic prop-erties of ancient clays that have been repeatedly heated at the past at temperatures higher than 400◦Cappear to be more stable and representative of the equivalent firing temperature. This study confirmsthat the reversibility of thermomagnetic curves can be a useful indicator of ancient firing temperaturesin the case of baked clays that have experienced multiple heatings at the past while caution should bepaid on its general use as archaeo-temperature marker
The importance of multidisciplinary dating in rescue excavations: The case of Santhià, Northern Italy
No full textStudio delle proprietà magnetiche di un forno mobile
No full textIn questo contributo si riportano i risultati dello studio
delle proprietà magnetiche di uno dei forni mobili di Villa
del Foro (Giaretti et al., Con la terra e con il fuoco. Installazioni
fisse e mobili, supra, figg. 167-169) (Cast 3;
fig. 186, 2) (Venturino Gambari et al. 2010b; 2017).
La caratterizzazione dei materiali si è basata principalmente
sullo studio delle loro proprietà magnetiche con l’ausilio
di analisi strutturali mediante diffrattometria di raggi-X. In
particolare, sono state effettuate misure delle seguenti
grandezze di tipo magnetico: rimanenza magnetica naturale
(NRM), suscettività magnetica, cicli d’isteresi e curve
termomagnetiche. Le misure mediante diffrattometria di
raggi-X sono state condotte su campioni ridotti in polvere
(XRPD) in un mortaio di agata (Reboldi 2015-2016).
L’analisi del forno Cast 3 interessa per un’eventuale determinazione
delle temperature raggiunte durante il suo
utilizzo, possibile tramite l’analisi delle trasformazioni
chimico-fisiche non reversibili indotte da riscaldamenti
sperimentali in campioni della struttura portati a temperature
superiori a quelle subite nell’antichità.
Lo studio di variazioni delle proprietà fisico-chimiche
di frammenti ceramici in funzione della temperatura è
possibile attraverso una misura continua delle proprietà
magnetiche, con l’utilizzo di un magnetometro a campione
vibrante (VSM) corredato di un forno a resistenze.
Il VSM, infatti, oltre a fornire il rilievo delle proprietà magnetiche
a temperatura ambiente per mezzo di curve
di magnetizzazione e cicli di isteresi, può fornire curve
termomagnetiche aggiungendo, alle condizioni variabili,
la temperatura. Questa modalità investigativa è nota
e ampiamente utilizzata per individuare e identificare
i minerali magnetici presenti in rocce, manufatti e altri
campioni naturali (Liu et al. 2012; Jordanova et al. 2019).
Applicata ai campioni di Villa del Foro permette di
ottenere indizi utili sulla mineralogia magnetica ed eventualmente
sulle temperature raggiunte durante l’utilizzo
della struttura (Tema - Ferrara 2019).
Le analisi di diffrattometria delle polveri (XRPD) sono
state svolte al fine di caratterizzare la composizione
mineralogica dei materiali, in genere formati da una
miscela complessa di fasi cristalline, che può comprendere
diversi tipi di minerali argillosi uniti a quarzo,
feldspati e calcite, oltre ai minerali magnetici principalmente
costituiti da ossidi di ferro, come magnetite,
ematite, goethite e maghemite
Il rinvenimento della fornace seicentesca di via Albussano a Chieri: analisi integrata dei dati archeologici, archeometrici e archivistici
No full textStudio di una fornace postmedievale rinvenuta a Chieri. Applicazione del metodo di datazione per archeomagnetism
Determining the use of ancient ceramic artefacts through combined morphological and magnetic analyses : the case of Villa del Foro, Northern Italy
No full textEven though multidisciplinary approaches are widely used for the investigation of archaeological findings, magnetic analyses are still little exploited and only rarely applied to the determination of ancient artefacts use. Here, we present the results of a combined archaeological, morphological, and magnetic study carried out on the ring-shaped clay artefacts found in large quantities at the Iron Age site of Villa del Foro (Alessandria, Northern Italy). The shape and the significant number of such artefacts make their archaeometric investigation very interesting in order to understand the technological conditions of their production and use. A morphological investigation carried out on 640 fragments showed inhomogeneity in their dimensions, color, form, and clay refinement. Magnetic measurements show thermal stability after heat treatment up to around 500–600 °C, while further heating at higher temperature introduces some magnetic mineralogy changes. 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 to 450 °C. The results obtained indicate that the investigated ring-shaped artefacts were baked during their manufacture at temperatures of at least 600 °C. The archaeomagnetic investigation does not show any systematic evidence for magnetic components related to cooking activities and it is therefore suggested that the rings were used as weight looms and baked only during their production procedures. Such pilot study can be used as reference for the identification and study of similar objects found in other archaeological sites worldwide
Palaeotemperature estimation of the pyroclastic deposit covering the pre-Minoan palaeosol at Megalochory Quarry, Santorini (Greece): Evidence from magnetic measurements.
No full textDating of ancient kilns: A combined archaeomagnetic and thermoluminescence analysis applied to a brick workshop at Kato Achaia, Greece
No full textThe Earth's magnetic field in Italy during the Neolithic period: New data from the Early Neolithic site of Portonovo (Marche, Italy)
No full textArchaeomagnetic and thermoluminescence combined analysis as a promising dating tool in archaeology: a case study of an ancient workshop, Kato Achaia, Greece
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