PALEOMAGNETIC RECORD OVER THE PAST 35,000 YEARS OF A SEDIMENT CORE FROM OFF SHIKOKU, SOUTHWEST JAPAN

The paleomagnetism of a sediment core (KT89-18, P4), recovered from the sea floor off Southwest Japan, was studied to investigate geomagnetic field variation over the past 35,000 years. Alternating fields demagnetization revealed that the remanent magnetization of the unconsolidated sediments was stable and not affected by any secondary overprints. C-14 datings were made on 21 horizons, using a Tandetron accelerator mass spectrometer, providing a detailed time scale to the core. The inclination record agrees with that from Lake Biwa [Kawai et al., 1975], and supports the existence of the geomagnetic excursions which had been found in the Lake Biwa core. The ages of the excursions are estimated to be during ca. 32 ky.B.P. is similar to ca. 28 ky.B.P. and ca. 26 ky.B.P. is similar to ca. 24 ky.B.P.