MAGNETOSTRATIGRAPHY OF CORE GX149 FROM THE WEST PHILIPPINE SEA

Rock magnetic and paleomagnetic studies were carried out for the core GX149 taken from the western West Philippine Sea. The magnetic carrier in sediments is dominated by low coercivity magnetite within the pseudo-single-domain (PSD) in size. The natural remanent magnetization (NRM) of samples ranges from 1.07×10^-7 to 6.51×10^-7 Am² with a mean of 3.33×10^-7 Am². Most samples could acquire well-defined, steadily characteristic remanence component after stepwise alternating field (AF) demagnetization upto 80mT. The geomagnetic inclinations of most samples are positive, suggesting that the whole core of GX149 falls in the Brunhes epoch. The shallowing of inclinations of the sediments are common in core GX149, and the degree of inclination bias increases from top to the bottom. The cause for the inclination bias is most likely the syn/post-depositional compaction of sediments. The sedimentation rate is estimated in a range of 0.79~2.42 cm/ka for the whole sequence. The maximum geochronological constraint for sedimentation duration of core GX149 is estimated 256.2~781ka by comparing with other sediment cores in adjacent areas.