MAGNETOSTRATIGRAPHIC DATA FROM LATE QUATERNARY SEDIMENTS FROM THE YERMAK PLATEAU, ARCTIC-OCEAN - EVIDENCE FOR 4 GEOMAGNETIC POLARITY EVENTS WITHIN THE LAST 170 KA OF THE BRUNHES CHRON

Palaeomagnetic investigations of two sediment cores recovered from RV Polarstern near the eastern slope of the Yermak Plateau (sites PS 1533 and PS 2212) reveal convincing evidence for four polarity events of the Earth's magnetic field during the last 170 Ka. A comprehensive rock magnetic study of the sediments proved that fine-grained magnetite is the principal carrier of the remanent magnetization. No changes in magneto-mineralogy across the polarity transitions in the sediments investigated were found. Calcareous nannofossil biostratigraphy, AMS-C-14 (accelerated mass spectrometry) and oxygen isotope data, and Be-10 and Th-230 stratigraphics yielded age ranges of 24-29 Ka for the Mono Lake event, 34-43 Ka for the Laschamp event, 72-86 Ka for the Norwegian-Greenland Sea event and 118-128 Ka for the Blake event. Two reverse polarity samples at the base of core PS 2212-3 KAL are interpreted as the termination of the Biwa I event (171-181 Ka). The events exhibit full inversion of inclination in both cores. The data suggest that the transition process of the Earth's magnetic field during such polarity events requires some 1 Ka.