Statistical analysis of palaeomagnetic data during the last four centuries: evidence of systematic inclination shallowing in lava flow records.

The main objective of this work is to compare directional (declination and inclination) volcanic and archaeomagnetic data for the last four centuries (1600–1990) with the historical geomagnetic predictions given by the GUFM1 model which spans from 1590 to 1990. The results show statistical agreement between archaeomagnetic data and directions given by the geomagnetic field model. However, when comparing the volcanic data with the model predictions, marked inclination shallowing is observed. This systematically lower inclination has already been observed in local palaeomagnetic studies (Italy, Mexico and Hawaii) for the 20th century, by comparing recent lava flows with the International Reference Geomagnetic Field (IGRF) model. Here, we show how this inclination shallowing is statistically present at worldwide scale for the last 400 years with mean inclination deviation around 3 degrees lower than the historical geomagnetic field model predictions.