A DETAILED PALEOMAGNETIC RECORD FOR THE LAST INTERGLACIAL PERIOD

A palaeomagnetic investigation of a late Quaternary loess-palaeosol sequence in central China has revealed two episodes of anomalous geomagnetic field behaviour in the lower and upper parts of soil complex S1, which spans the last interglacial interval. Comparison of the magnetic susceptibility record with the deep-sea oxygen isotope stratigraphy provides a chronology which has been used to estimate the age and duration of these episodes. The age of the younger episode has been estimated at 89-75 ka, comparable with the age of a geomagnetic event recognised from sediments in the Norwegian-Greenland Sea and Arctic Ocean. The older episode is associated with a broad low in relative palaeointensity which has been assigned to the time interval 130-110 ka. This is consistent with existing age estimates of the so-called Blake Event. In contrast to a published record of the Blake Event from the loess at Xining, which shows three short episodes of almost full reversed polarity, in the current record the Blake Event is represented by a loop in the VGP path which passes through shallow southern latitudes. Although both episodes occur within the same part of soil complex S1, the difference between the two records implies a greater degree of smoothing of the geomagnetic signal in the Huanxian record. This is probably a reflection of the lower accumulation rate at Huanxian and may also indicate a greater time constant for the remanence aquisition at this site.