Reconstructing the behavior of Earth’s magnetic field during archaeological periods is crucial for both achieving a better understanding of the field and related natural phenomena and for providing a basis for absolute dating archaeological materials. In new research, University College London’s Professor Mark Altaweel and his colleagues analyzed 32 inscribed baked bricks from Mesopotamia from the 3rd-1st millennia BCE (the reigns of 12 Mesopotamian kings).
“We often depend on dating methods such as radiocarbon dates to get a sense of chronology in ancient Mesopotamia,” said Professor Altaweel, co-author of a paper published in the Proceedings of the National Academy of Sciences.
“However, some of the most common cultural remains, such as bricks and ceramics, cannot typically be easily dated because they don’t contain organic material.”
“This work now helps create an important dating baseline that allows others to benefit from absolute dating using archaeomagnetism.”
The magnetic field of the Earth weakens and strengthens over time, changes which imprint a distinct signature on hot minerals that are sensitive to the magnetic field.
The study authors analyzed the latent magnetic signature in grains of iron oxide minerals embedded in 32 clay bricks originating from archaeological sites throughout Mesopotamia, which now overlaps with modern day Iraq.
The strength of the magnetic field was imprinted upon the minerals when they were first fired by the brickmakers thousands of years ago.
At the time they were made, each brick was inscribed with the name of the reigning king which archaeologists have dated to a range of likely timespans.
Together, the imprinted name and the measured magnetic strength of the iron oxide grains offered a historical map of the changes to the strength of the Earth’s magnetic field.
The researchers were able to confirm the existence of the Levantine Iron Age geomagnetic Anomaly, a period when Earth’s magnetic field…
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