Reconstructing Late Pleistocene to Prehistorical Holocene Geomagnetic Field Variations From La Palma Lava Flows (Canary Islands, Spain): Unraveling Viscous Components

Abstract

We present new vector paleomagnetic data from 13 radiometrically dated lava-flows in southern La Palma (Canary Islands) spanning from 1 to 56 ka, which covers most of the Late Pleistocene to prehistoric Holocene volcanic record in the island. Using a paleointensity multimethod approach including Thellier-type and Shaw-type techniques, and combining detailed rock magnetic and mineralogical analyses, we assess the reliability and possible biases in paleointensity estimations in volcanic rocks affected by low-temperature oxidation and coarse ferromagnetic grains. Results indicate a strong viscous component linked to maghemitization, which compromises paleointensity reliability and accuracy. Low temperature demagnetization pretreatments significantly mitigated the viscosity contribution, improving success rates by highlighting the original thermoremanent magnetization (TRM) and revealing possible overestimations in standard Thellier-type treated samples affected by maghemitization. The full vector results, compared with several paleosecular variation curves, exhibited both low and high field intensity periods, including a relative paleointensity minimum at ∼27 ka (VADM ∼26 ZAm2) and the record of the Levant intensity high (VADM ∼108 ZAm2). This study contributes with valuable constraints for improving geomagnetic models, especially for low-latitude regions, and underscores the importance of integrating magnetic mineralogy with paleointensity protocols to mitigate bias in geomagnetic reconstructions.