Journal Article

Geomagnetic Field Intensity During the First Millennium BCE From Royal Judean Storage Jars: Constraining the Duration of the Levantine Iron Age Anomaly

Sabar, R., Freud, L., Leibner, U., Vaknin, Y., Sandhaus, D., Hassul, E., Shaar, R., Agnon, A., Gallet, Y., Lipschits, O.

2024

Overview

The rich and extensively studied archaeological record of the Near East provides an opportunity to develop a comprehensive archaeomagnetic dataset for exploring the behavior of the geomagnetic field with high precision. The Levantine archaeomagnetic curve (LAC) project is an ongoing effort to develop a continuous high‐resolution geomagnetic intensity curve for the Levant and Mesopotamia. The first version of the LAC covered the period between 3000 and 550 BCE. Here, we report archaeointensity data from 169 samples compiled into 32 groups dating between the 7th and the 1st centuries BCE aiming at extending the LAC up to the end of the first millennium BCE. Twenty‐two groups are assembled from storage jar handles bearing different types of royal seal impressions, which were used in Judah as part of a taxation administrative system. These groups are combined with 10 other groups of pottery assemblages, three of which are from Hellenistic destruction layers dated using radiocarbon and coins. The new curve shows that the Levantine Iron Age Anomaly (LIAA) spanned 550 years (1100 ‐ 550 BCE) and that the rate of decline during the last spike around 600 BCE could have reached ∼0.6 μT/year. During the 6th century, the virtual axial dipole moment (VADM) dropped from 160 ZAm2 to 125 ZAm2 after which field intensity only slightly increased to 135 ZAm2, until another considerable decline to ∼90 ZAm2 during the 3rd to the 1st centuries BCE. We highlight the archaeomagnetic implication of the new curve in inferring the relative chronological relationship between different stamp types. Plain Language Summary The Earth's magnetic field is continuously changing both in time and space in an unpredictable manner. A detailed description of how the magnetic field has changed throughout Earth's history offers constraints on our understanding of the mechanism generating the field in Earth's core. In this study, we reconstruct the intensity of the past field using an assemblage of well‐dated archaeological materials from Israel, dated to the Assyrian, Babylonian, Persian, Hellenistic and Hasmonean periods. This work is part of an ongoing effort to procure a high‐resolution curve describing the changes in field intensity for the Levant and Mesopotamia over the past several millennia. With the new data, we calculate the curve for the first three millennia BCE. The curve provides further details on an anomalous behavior of the field between 1100 BCE and 550 BCE, termed the Levantine Iron Age Anomaly (LIAA), during which the field intensity and its rate of change were significantly higher than today's. In addition, the curve forms the basis for an archaeomagnetic dating tool, which can be especially useful for periods when traditional archaeological dating methods fail to provide precise ages due to large uncertainties in radiocarbon dates. Key Points Archaeomagnetic intensity data from 32 groups of pottery in Israel dated between the 7th and the 1st centuries BCE The second generation of the Levantine Archaeomagnetic Curve (LAC.v.2.0) covering the last three millennia BCE The new data constrain the duration of the Levantine Iron Age Anomaly (LIAA) from 1100 BCE to 550 BCE

• Publisher: John Wiley & Sons, Inc,AGU and the Geochemical Society,Wiley
• Subject: Archaeology / Archaeology and Prehistory / archaeomagnetism / Carbon 14 / Earth core / Earth Sciences / Geomagnetic field / geomagnetic secular variation / Geophysics / Hellenistic / Humanities and Social Sciences / Iron / Iron Age / Levantine iron age anomaly / Magnetic field / Magnetic fields / paleointensity / paleomagnetism / Radiocarbon dating / Sciences of the Universe / Taxation