Atmospheric methane levels increased over geological formations in Northern Siberia following a heat wave in 2020, suggesting that permafrost thaw releases methane from reservoirs.
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Contributed by Lisa Tauxe, June 28, 2021 (sent for review January 17, 2021; reviewed by Maxwell Brown and Monika Korte)
Significance
The Earth’s magnetic field has changed significantly in the past with implications for related phenomena, such as deep-Earth processes and evolution of life. Accurate datasets of its past behavior also provide a dating tool. We present data from Neolithic ceramics and flint from Jordan. Our results are among the oldest in the Levant, covering a period of major changes in human history. The data help in refining the resolution of the archaeomagnetic curve, in turn enhancing its use as a dating tool and for understanding past field behavior. Moreover, we demonstrate the potential for the use of flint material, the most common raw material for the manufacturing of tools in the entire Paleolithic and younger periods, for archaeointensity investigations.
Abstract
Constraining secular variation of the Earth’s magnetic field strength in the past is fundamental to understanding short-term processes of the geodynamo. Such records also constitute a powerful and independent dating tool for archaeological sites and geological formations. In this study, we present 11 robust archaeointensity results from Pre-Pottery to Pottery Neolithic Jordan that are based on both clay and flint (chert) artifacts. Two of these results constitute the oldest archaeointensity data for the entire Levant, ancient Egypt, Turkey, and Mesopotamia, extending the archaeomagnetic reference curve for the Holocene. Virtual Axial Dipole Moments (VADMs) show that the Earth’s magnetic field in the Southern Levant was weak (about two-thirds the present field) at around 7600 BCE, recovering its strength to greater than the present field around 7000 BCE, and gradually weakening again around 5200 BCE. In addition, successful results obtained from burnt flint demonstrate the potential of this very common, and yet rarely used, material in archaeomagnetic research, in particular for prehistoric periods from the first use of fire to the invention of pottery.
Footnotes
- ↵1To whom correspondence may be addressed. Email: ltauxe{at}ucsd.edu.
Author contributions: L.T. and E.B.-Y. designed research; A.D.C., T.E.L., and M.N. performed research; A.D.C. and L.T. contributed new reagents/analytic tools; A.D.C., L.T., and E.B.-Y. analyzed data; A.D.C., L.T., T.E.L., and E.B.-Y. wrote the paper with contributions from F.F.; M.N. provided archaeological context; and F.F. provided support for the first author.
Reviewers: M.B., University of Minnesota; and M.K., Helmholtz Centre Potsdam-GFZ German Research Centre for Geosciences.
The authors declare no competing interest.
Data Availability
Rock and paleomagnetic data have been deposited in the Magnetics Information Consortium database (https://earthref.org/MagIC/17126).
Published under the PNAS license.
References
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The strength of the Earth’s magnetic field from Pre-Pottery to Pottery Neolithic, Jordan
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- Physical Sciences
- Earth, Atmospheric, and Planetary Sciences
- Social Sciences
- Anthropology
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