Abstract: In paleomagnetism, periods of high field intensity have been largely ignored in favor of the more spectacular
directional changes associated with low field intensity periods of excursions and reversals. Hence, questions
such as how strong the field can get and how fast changes occur are still open. In this paper we report on data
obtained from an archaeometallurgical excavation in the Middle East, designed specifically for
archaeomagnetic sampling. We measured 342 specimens from 72 samples collected from a 6.1 m mound
of well stratified copper production debris at the early Iron Age (12th–9th centuries BCE) site of Khirbat en-
Nahas in Southern Jordan. Seventeen samples spanning 200 yr yielded excellent archaeointensity results that
demonstrate rapid changes in field intensity in a period of overall high field values. The results display a
remarkable spike in field strength, with sample mean values of over 120 μT (compared to the current field
strength of 44 μT). A suite of 13 radiocarbon dates intimately associated with our samples, tight control of
sample location and relative stratigraphy provide tight constraints on the rate and magnitude of changes in
archaeomagnetic field intensities.
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Location of Study: Faynan Copper Ore District in Southern Jordan, with the archaeological site of Khirbat en-Nahas (KEN), the largest Iron Age copper production center in the Southern Levant. |
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Details of section: Khirbat en-Nahas, area M (Faynan Copper Ore District, Jordan): drawing of the eastern (left) and southern (right) walls of excavation pit in a ‘slag mound’ depicting multi-layer sequence of copper production debris and location of all samples with ‘successful’ archaeointensity specimens obtained directly from these walls (‘B’ numbers for Baskets) or from the associated excavation ( ‘L’ numbers for Loci). Results from radiocarbon samples of Levy et al. (2008) are marked by circles. Also indicated as heavy lines are the reference stratigraphic horizons for composite stratigraphic height measurements. |
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The Levantine Master Intensity curve and the Khirbat en Nahas geomagnetic field spike:
Virtual axial dipole moments (VADMs) of the geomagnetic field for the last seven millennia and the spike recorded in this study (note that ‘Z’ stands for 10^21). Southern Levantine data are from Ben-Yosef et al. (2008a,b) (red circles), northern Levantine data are from Genevey et al. (2003) and Gallet et al. (2006) (grey squares), and the CALS7k.2 model is of Korte and Constable 2005) (black curve). Inset shows data from this study; a line is sketched through the data points as a visual aid, emphasizing trends and possible major hiatus. Note changes of scale, and the boundary line of Strata M3/M2 discussed in the article. |
References: Ben-Yosef, E., H. Ron, L. Tauxe, A. Agnon, A. Genevey, T.E. Levy, U. Avner and M. Najjar, Application of copper slag in archeointensity research, J. Geophys. Res., 113, B08101, doi:10.1029/2007JB005235, 2008. Ben-Yosef, E., Tauxe, L., Ron, H., Agnon, A., Avner, U., Najjar, M., and Levy, T.E., A new approach for geomagnetic archaeointensity research: Insights on ancient metallurgy in the Southern Levant, J. Archeol. Sci., 35, 2863-2879, 2008. Ben-Yosef, E., Tauxe, L., Levy, T.E., Shaar, R., Ron, H., and Najjar, M., Archaeomagnetic intensity spike recorded in high resolution slag deposit from historical biblical archaeology site in Southern Jordan, Earth Planet. Sci. Lett., doi:10.1016/j.epsl.2009.09.001, 2009. Gallet, Y., Genevey, A., Le Goff, M., Fluteau, F., Eshraghi, S. A., 2006. Possible impact of the Earth's magnetic field on the history of ancient civilizations. Earth Planet. Sci. Lett.246, 17-26. Genevey, A., Gallet, Y., Margueron, J., 2003. Eight thousand years of geomagnetic field intensity variations in the eastern Mediterranean. J. Geophys. Res108, doi:10.1029/2001JB001612. Korte, M., Constable, C., 2005. Continuous geomagnetic field models for the past 7 millennia: 2. CALS7K. Geochem., Geophys., Geosyst.6, Q02H16: DOI 10.1029/2004GC000801. Levy, T. E., T. Higham, C. Bronk-Ramsey, N. G. Smith, E. Ben Yosef, M. Robinson, S. Munger, K. Knabb, J. Schultz, M. Najjar, and L. Tauxe. 2008. High Precision Radiocarbon Dating and Historical Biblical Archaeology in Southern Jordan. Proceedings of the National Academy of Science, 105, 16460-16465. doi:10.1073/pnas.080495010
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