Geomagnetic field intensity: How high can it get? How fast can it change? Constraints from Iron Age copper slag |
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| Authors: | Ron Shaar Erez Ben-Yosef Hagai Ron Lisa Tauxe Amotz Agnon Ronit Kessel |
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| Institution: | 1. The Institute of Earth Sciences, The Hebrew University of Jerusalem, Givat Ram, Jerusalem, 91904, Israel;2. Department of Anthropology, University of California, San Diego, La Jolla, CA, 92093, USA;3. Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, 92093, USA;1. Department of Earth and Planetary Science, Weizmann Institute of Science, Israel;2. Planetary Science Institute, Tucson, AZ, USA;3. Institute of Earth Sciences, Hebrew University of Jerusalem, Israel;4. Institute of Geology, Czech Academy of Sciences, Prague, Czech Republic;5. Department of Applied Geophysics, Charles University, Prague, Czech Republic;6. Geophysical Institute, University of Alaska Fairbanks, AK, USA;1. Paleomagnetic laboratory Fort Hoofddijk, Department of Earth Sciences, Utrecht University, Budapestlaan 17, 3584 CD Utrecht, The Netherlands;2. Geomagnetism Laboratory, School of Environmental Sciences, University of Liverpool, Oliver Lodge Labs, Oxford Street, Liverpool L69 7ZE, UK;1. Centre de Recherches en Physique Appliquée à l’Archéologie, UMR 5060, Université de Bordeaux 3, CNRS, France;2. Géosciences-Rennes, UMR 6118, Université de Rennes 1, CNRS, Campus de Beaulieu, Bat 15, CS 74205, 35042 Rennes Cedex, France;1. Department of Planetology, Faculty of Science, Kobe University, Kobe 657-8501, Japan;2. Priority Organization for Innovation and Excellence, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555, Japan;3. Department of Earth Sciences, Nara University of Education, Nara 630-8528, Japan;4. Institute of GeoHistory, Susai 1599, Akaiwa, Okayama 701-2503, Japan;1. Instituto de Geociencias (IGEO), CSIC-UCM, Ciudad Universitaria, 28040 Madrid, Spain;2. Departamento Física de la Tierra I, Facultad de Ciencias Físicas, Universidad Complutense, 28040 Madrid, Spain;3. Géosciences-Rennes, UMR 6118, CNRS, Université de Rennes 1, Campus de Beaulieu, Bât. 15, CS 74205, 35042 Rennes, France;4. Freelance archeologist, Granada, Spain;5. Escuela de Estudios Árabes EEA-CSIC, Frailes de la Victoria, 1810 Granada, Spain;6. Centre de Recherches en Physique Appliquée à l''Archéologie, UMR 5060, CNRS, Université de Bordeaux 3, France;1. Paleomagnetic Laboratory Fort Hoofddijk, Department of Earth Sciences, University of Utrecht, Budapestlaan 17, 3584 CD Utrecht, the Netherlands;2. Geomagnetism Laboratory, Oliver Lodge Laboratories, Department of Earth and Ocean Sciences, University of Liverpool, Liverpool L69 7ZE, UK;3. Department of Philosophy, Arts and Humanities and Oriental Studies, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy;4. Department of Anthropology and Classical Studies, University of Akron, Akron, OH 44325-1910, USA;5. Department of Archaeology, Faculty of Arts and Sciences, Kocaeli University, Kocaeli, Turkey;6. Department of Archaeology, Faculty of Letters, Cumhuriyet University, Sivas, Turkey |
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| Abstract: | The intensity of the geomagnetic field varies over different time scales. Yet, constraints on the maximum intensity of the field as well as for its maximum rate of change are inadequate due to poor temporal resolution and large uncertainties in the geomagnetic record. The purpose of this study is to place firm limits on these fundamental properties by constructing a high-resolution archaeointensity record of the Levant from the 11th century to the early 9th century BCE, a period over which the geomagnetic field reached its maximum intensity in Eurasia over the past 50,000 years. We investigate a 14C-dated sequence of ten layers of slag material, which accumulated within an ancient industrial waste mound of an Iron Age copper-smelting site in southern Israel. Depositional stratigraphy constrains relative ages of samples analyzed for paleointensity, and 14C dates from different horizons of the mound constrain the age of the whole sequence. The analysis yielded 35 paleointenisty data points with accuracy better than 94% and precision better than 6%, covering a period of less than 350 years, most probably 200 years. We construct a new high-resolution quasi-continuous archaeointensity curve of the Levant that displays two dramatic spikes in geomagnetic intensity, each corresponding to virtual axial dipole moment (VADM) in excess of 200 ZAm2. The geomagnetic spikes rise and fall over a period of less than 30 years and are associated with VADM fluctuations of at least 70 ZAm2. Thus, the Levantine archaeomagnetic record places new constraints on maximum geomagnetic intensity as well as for its rate of change. Yet, it is not clear whether the geomagnetic spikes are local non-dipolar features or a geomagnetic dipolar phenomenon. |
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