The second generation of the Levantine Archaeomagnetic Curve (LAC.v.2.0) ~6300 BCE - 300 CE: Insight into the evolution of the Iron Age anomaly, geomagnetic spikes and secular variation rates

The vast number of well-dated archaeological sites in the Levant and Mesopotamia, provide a unique opportunity for detailed archaeomagnetic research. In an effort to exploit the full archaeomagnetic potential of this region, we assemble an archaeointensity compilation based on two separate datasets which were constructed independently in different regions using different methods. The Mesopotamian dataset, comprised of 123 groups of samples (fragments) collected from Syria and north-western Iraq was analyzed for the most part using the Triaxe method. The Levantine dataset comprised of more than 150 groups of samples collected from Israel was analyzed using Thellier-IZZI-MagIC method. Together, these partially overlapped datasets compose a continuous record that spans over more than six millennia - from ~6300 BCE to 300 CE. Some intervals in this time span, such as 2000 BCE - 500 BCE and 300 BCE- 300 CE, include at least one context per century with a secure absolute age, which is based on radiocarbon or clear historically-dated events, providing sub-centennial temporal resolution. With these data we construct the second generation of the Levantine Archaeomagnetic Curve (LAC.v.2.0) that enables robust high-resolution analysis of the rates and amplitudes of geomagnetic secular variations. The LAC exhibits four geomagnetic spikes associated with the Levantine Iron Age Anomaly (LIAA), between 1050 and 600 BCE, with virtual axial dipole moment (VADM) reaching values of 155-162 ZAm² - higher than predicted by currently reconstructed geomagnetic field models. Rates of VADM change associated with the four spikes are ~0.7-1.1 ZAm²/year – at least twice the maximum rate inferred from direct observations, which began ~190 years ago. The increase leading to the first spike from ~1750 BCE to ~1050 BCE depicts the Holocene largest change in field intensity. The highest value in the LAC is more than 3 times greater than the lowest value providing conservative bounds for the local variability of the geomagnetic field. Finally, we present a new compilation of archaeomagnetic directions obtained from 70 structures in Israel which, together with the intensity curve, provide a further step towards a full-vector description of the field.