The evolution of the Levantine Iron Age geomagnetic Anomaly captured in Mediterranean sediments

Abstract

The geomagnetic field can vary dramatically over only decades and thousands of kilometers; the Levantine Iron Age geomagnetic Anomaly (LIAA) is probably the best-known example of such short-lived feature of the Earth's magnetic field. Yet, the size, shape and temporal variations of this phenomenon are currently still enigmatic. Here we provide continuous full-vector records of the variations in the geomagnetic field from three marine sediment cores from the Mediterranean, to better constrain the LIAA in time and space. The cores are located (1) between Spain and Morocco (Alboran), (2) East of Calabria, Italy (Taranto Gulf), and (3) North of the Nile Delta (Levant). Geomagnetic field variations between 6000 BC and 1000 AD are captured for a total of 681 samples. Rock magnetic analyses indicate the sediment cores as reliable recorders for geomagnetic field variations. Between 750 and 250 BC, high intensities are observed for the Levant and Taranto Gulf core, with their peak – 150 ZAm2 at 500 BC – shortly after the occurrence of the LIAA. Low paleointensities are obtained from the Alboran core providing a western limit of the extent of the LIAA until at least 250 BC. From 500 BC onwards the location of the highest paleointensities moves slightly westwards while diminishing in intensity. The LIAA moves from 40 to 55° East at 1000 BC to ∼25° East at 0 AD, while decaying from ∼150 ZAm2 to ∼110 ZAm2 in the same time span. This results in a westward movement of 15–30° in 1000 yr.