Refining the Iberian Palaeosecular Variation Curve for the 2.5 kyr before 0 CE and contributing to the understanding of Earth’s magnetic field evolution in Eurasia

Summary The scarcity of high-quality archaeomagnetic data from the Bronze and Iron Ages in the Iberian Peninsula hampers a detailed understanding of geomagnetic field behaviour during this key period. This study presents new archaeomagnetic results from 29 combustion structures and 82 pottery fragments from 13 archaeological sites in Spain dated between the Bronze and Iron Ages (2.5-0 kyrs BCE). Samples were analysed using the classical Thellier–Thellier method for palaeointensity determination, including corrections for thermoremanent magnetisation anisotropy and cooling rate, and alternating-field and thermal demagnetisation experiments for directional determinations. Rock magnetic experiments indicate that low-Ti titanomagnetite is the primary carrier of the natural remanent magnetization and evidence of stable maghemite in some ceramics. Strict selection criteria were applied to ensure the reliability of the archaeomagnetic determinations, yielding 37 palaeointensity determinations and 18 directional results. The new Iberian archaeomagnetic dataset, together with critically selected published data, was used to construct a new full-vector Iberian Palaeosecular Variation Curve (PSVC) covering the last 2500 years BCE. For the Late Bronze and Iron Ages, the new dataset is consistent with the SHAWQ-Iron Age model, supporting an intensity maximum around 500 BCE. In contrast, the easterly declinations of approximately 25–30° observed around 1500 BCE are underestimated by the SHA.DIF.14k and SCHA.DIF.4k models. The suitability of the new PSVC for archaeomagnetic dating was tested by dating three combustion structures. To investigate the behaviour of the Earth's Magnetic Field, we analysed the new dataset over the last 3500 BCE. The results indicate that high VADM values (∼12 × 10²² Am²) first emerged around 1400 BCE in eastern Asia and propagated west-northwestward at an estimated rate of 0.1–0.2°/yr, likely associated with the westward expansion of the Levantine Iron Age Anomaly. The anomaly intensifies markedly in the Levantine region before continuing its westward spreading, reaching Iberia around 500 BCE.