Rock-magnetic and archaeomagnetic investigations on archaeological artifacts from Maharashtra, India

Archaeointensity and rock-magnetic studies were undertaken on 49 baked clay artifacts from four archaeological sites (Ter, Junnar, Nalasopara and Kanheri), in Maharashtra, India. The rock-magnetic properties, including bulk magnetic susceptibility, magnetic remanence and thermomagnetic analysis, indicate the presence of a low coercivity magnetite in fine (superparamagnetic, single domain) grain-sizes. The ratio of ARM to SIRM, the reversible high temperature susceptibility curves and the 3IRM tests also indicate that the artifacts dominantly possess fine grained magnetic particles, carrying a stable TRM. Archaeointensity was estimated using the Coe's modified Thellier method corresponding to linear behaviour of NRM loss and TRM gained plots, which were evaluated with ThellierTool4.0 software. Cooling rate and anisotropy of TRM corrections were applied and the corrected intensities were used to calculate a mean archaeointensity value for each one of the four sites. The new archaeointensity values were plotted along the existing Indian archaeointensity values derived only from archaeological artifacts and were compared with the SHA.DIF.14k and ARCH10k.1 global models' predictions. The present study aims to improve the overall understanding of Indian geomagnetic field variation in the past by providing new high-quality archaeointensity results. However, still more archaeointensity values are required to develop a reliable secular variation curve for India.