MAGNETOSTRATIGRAPHIC DATA FROM LATE QUATERNARY SEDIMENTS FROM THE YERMAK PLATEAU, ARCTIC-OCEAN - EVIDENCE FOR 4 GEOMAGNETIC POLARITY EVENTSWITHIN 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 t he 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 ma gneto-mineralogy across the polarity transitions in the sediments inve stigated 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 Lak e event, 34-43 Ka for the Laschamp event, 72-86 Ka for the Norwegian-G reenland Sea event and 118-128 Ka for the Blake event. Two reverse pol arity 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 tra nsition process of the Earth's magnetic field during such polarity eve nts requires some 1 Ka.