The Gauss and Matuyama recorded in drift sediments from the North Atlantic: preliminary study from IODP Expedition 395C.

Drift sediments are characterized by a rapid accumulation rate (≥10 cm/kyr), which can provide high-resolution records of the geomagnetic field behavior. Previous ocean drilling in the North Atlantic (e.g., ODP Leg 162 and IODP Exp 306) discovered magnetic instabilities of short duration, such as the Iceland Basin Excursion (188 ka). These records have contributed to our understanding of Earth’s magnetic field variations in the geological past and the foundation of the Geomagnetic Instability Time Scale (GITS) in the Quaternary (0-2.58 Ma). Between 2020 and 2023, IODP Expeditions 384, 395C, and 395 drilled six sites: five along a transect on the eastern side of the modern Mid-Atlantic Ridge (between 20-30°W at a latitude of ~60°N) and one on the western side, off the coast of Greenland. The expedition aims to investigate the formation of V-shaped ridges and V-shaped troughs in the Reykjanes Ridge and the evolution of deepwater currents. Shipboard paleomagnetic and microfossil data provided a preliminary age model for all sites, extending the regional record to 11 Ma. During the Expeditions(s), archive half sections were subjected to alternating field stepwise demagnetization cleaning of natural remanent magnetization. Shipboard paleomagnetic data were processed to remove edge effect, core disturbance, and are integrated with data from discrete samples. All directional data were interpreted, isolating the primary magnetization through the principal component analysis. The discrete samples confirm all polarity changes recognized in the shipboard inclination data. Here, we present the preliminary results from two of the sites drilled during the Expeditions 395C, U1555 (~2.7 Ma) and U1563 (~5.2 Ma), where most of the magnetic events (including excursions and reversals) reported in the Geomagnetic Instability Time Scale of the Quaternary are recognized. These high-resolution records provide the potential to extend the GITS further in the past, expanding the potential of using magnetic instabilities as a dating tool and help to refine our understanding of how the Earth’s magnetic field changed in the past.