Record of Geomagnetic Instabilities during the Brunhes: preliminary results from IODP Expeditions 384 and 395C from North Atlantic Ocean
Résumé
Throughout its history, the Earth’s magnetic field has undergone changes in its polarity. These changes vary in scale, from millennial (excursions) to hundreds of thousands or millions of years (reversal). Constraining the chronology of these geomagnetic instabilities is fundamental to understanding Earth’s dynamo processes and their surface expressions. Moreover, a detailed geomagnetic instability time scale (GITS) refines its applicability as an accurate correlation and dating tool (magnetostratigraphy) for sedimentary and volcanic sequences and it is fundamental to understanding several aspects of past climate. Indeed, periods of geomagnetic instability are usually associated with a weak field. This in turn weakens the efficiency of the Earth’s magnetic field shielding enhancing the production of cosmogenic isotopes which play a significant role on modulating climate by either directly or indirectly influencing factors such as the total or spectral solar irradiance. In this study, we present a preliminary record of geomagnetic instabilities during the Brunhes (0-0.778 Ma), based on intercorrelation of paleomagnetic data from five marine sedimentary cores collected during the IODP Expeditions 384 and 395C from the North Atlantic Ocean along the Reykjanes ridge. Two of the drilling sites are nearby the ODP Sites 983 and 984 (Channell et al., 2002) providing an opportunity to cross correlate our preliminary results.