Geomagnetic Field Variations in the Past: New Data, Applications and Recent Advances
In the last decades, palaeomagnetic research has provided important information about the past variation of the Earth's magnetic field (EMF) from its origin to the present day. However, questions regarding the origin and evolution of the EMF as well as the frequency and spatial distribution of its variations still remain open to debate. This Special Publication provides new insights into the study of the temporal and spatial evolution of the EMF presenting new data from palaeomagnetic and rock magnetic studies of archaeological materials, sediments and lavas. The papers presented cover a wide range of topics related to archaeology, stratigraphy and climate, including new data from several parts of the world, such as Europe, Africa, Australia, New Zealand, India and the Baltic Sea. This Special Publication aims to present an overview of the most recent secular variation studies and their use to disclose fundamental properties of the EMF evolution.
Rock-magnetic and archaeomagnetic investigations on archaeological artefacts from Maharashtra, India
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Published:September 23, 2020
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CiteCitation
K. Deenadayalan, P. B. Gawali, B. V. Lakshmi, Manish Rai, 2020. "Rock-magnetic and archaeomagnetic investigations on archaeological artefacts from Maharashtra, India", Geomagnetic Field Variations in the Past: New Data, Applications and Recent Advances, E. Tema, A. Di Chiara, E. Herrero-Bervera
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Abstract
Archaeointensity and rock-magnetic studies were undertaken on 49 baked clay artefacts from four archaeological sites (Ter, Junnar, Nalasopara and Kanheri) in Maharashtra, India. 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 anhysteretic remanent magnetization to saturation isothermal remanent magnetization, the reversible high-temperature susceptibility curves and the 3-axes isothermal remanent magnetization tests also indicate that the artefacts dominantly possess fine-grained magnetic particles, carrying a stable thermoremanent magnetization (TRM). Archaeointensity was estimated using Coe's modified Thellier method corresponding to the linear behaviour of natural remanent magnetization loss and TRM gained plots, which were evaluated with ThellierTool4.0 software. Cooling rate and anisotropy of the 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 artefacts, 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.
- anisotropy
- archaeological sites
- archaeology
- artifacts
- Asia
- computer programs
- data processing
- grain size
- India
- Indian Peninsula
- magnetic domains
- magnetic field
- magnetic intensity
- magnetic properties
- magnetic susceptibility
- magnetization
- Maharashtra India
- paleomagnetism
- particles
- remanent magnetization
- secular variations
- single domains
- temperature
- Thellier method
- thermal analysis
- thermomagnetic analysis
- Junnar India
- Ter India
- Kanheri India
- Nalasopara India