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<p>India has continuous instrumental geomagnetic field observatory records since 1841, which are essential for understanding present-day spatiotemporal variations in the Earth’s magnetic field. Although palaeogeomagnetic data from archaeological and geological contexts are available, a temporal gap persists between these historical geomagnetic variations and modern continuous records from magnetic observatories. This study presents three new reliable archaeointensities from the fourteenth to nineteenth centuries, serving as a crucial link to bridge the gap between instrumental and geological sample records. A detailed rock magnetic investigation of initial bulk magnetic susceptibility and remanence magnetization parameters along with their inter-magnetic ratios reveals a higher concentration of remanence-carrying magnetic minerals. These minerals are primarily composed of pseudo-single-domain (PSD) to single-domain (SD) grains, dominating the magnetic properties. The temperature-dependent magnetic susceptibility (χ − T) and thermal demagnetization of the orthogonal 3IRM curves reveal the presence of soft components such as magnetite and Ti-rich magnetite minerals, along with the absence of mineralogical alterations. Archaeointensity measurements were performed on 98 specimens from 49 samples using Coe’s modified Thellier–Thellier method, incorporating pTRM checks and corrections for TRM anisotropy and cooling rate, yielding a 72% success rate. After applying all the corrections and satisfying the given selection criteria, the mean archaeointensity is 39.92 ± 2.0&#xa0;μT for the Kolaba Fort (1800 ± 50 CE), 41.00 ± 1.0&#xa0;μT for Sindkhed Raja (1600 ± 50 CE), and 39.86 ± 1.4&#xa0;μT for the Parad site (1475 ± 245 CE). These new intensity data enhance the understanding of the geomagnetic field behaviour during the medieval and early modern periods by connecting these periods. Furthermore, it will refine the Indian palaeosecular variation curve and provide important constraints for improving regional geomagnetic field reconstructions and assessing low-latitude field variability during the late Holocene.</p>

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Archaeomagnetic studies on artefacts from Maharashtra, India: link between observatory records and archaeointensity data

  • 期刊论文

  • 发表日期：

    2026年2月24日

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  • Pradnya Mohite,
  • K. Deenadayalan,
  • B. V. Lakshmi,
  • Rajapandy P,
  • Juili Raut,
  • Manish Rai,
  • A. P. Dimri

摘要

India has continuous instrumental geomagnetic field observatory records since 1841, which are essential for understanding present-day spatiotemporal variations in the Earth’s magnetic field. Although palaeogeomagnetic data from archaeological and geological contexts are available, a temporal gap persists between these historical geomagnetic variations and modern continuous records from magnetic observatories. This study presents three new reliable archaeointensities from the fourteenth to nineteenth centuries, serving as a crucial link to bridge the gap between instrumental and geological sample records. A detailed rock magnetic investigation of initial bulk magnetic susceptibility and remanence magnetization parameters along with their inter-magnetic ratios reveals a higher concentration of remanence-carrying magnetic minerals. These minerals are primarily composed of pseudo-single-domain (PSD) to single-domain (SD) grains, dominating the magnetic properties. The temperature-dependent magnetic susceptibility (χ − T) and thermal demagnetization of the orthogonal 3IRM curves reveal the presence of soft components such as magnetite and Ti-rich magnetite minerals, along with the absence of mineralogical alterations. Archaeointensity measurements were performed on 98 specimens from 49 samples using Coe’s modified Thellier–Thellier method, incorporating pTRM checks and corrections for TRM anisotropy and cooling rate, yielding a 72% success rate. After applying all the corrections and satisfying the given selection criteria, the mean archaeointensity is 39.92 ± 2.0 μT for the Kolaba Fort (1800 ± 50 CE), 41.00 ± 1.0 μT for Sindkhed Raja (1600 ± 50 CE), and 39.86 ± 1.4 μT for the Parad site (1475 ± 245 CE). These new intensity data enhance the understanding of the geomagnetic field behaviour during the medieval and early modern periods by connecting these periods. Furthermore, it will refine the Indian palaeosecular variation curve and provide important constraints for improving regional geomagnetic field reconstructions and assessing low-latitude field variability during the late Holocene.