Estimation of the sources of pelagic sediments by sedimentation age

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Our study in 2008 is, in order to estimate the source in pelagic sediments, principal components analysis (PCA) was applied to the data matrix which was made by chemical compositions of sediments measured by instrumental neutron activation analysis and prompt gamma-ray analysis. The results of PCA represented 3-factor models in each sediment, explaining 58-98% of the total variations in the sediments. A comparison of eigenvectors of terrigenous elements indicated the existence of 2 sources. Group 1 is suggested to be continental dust, whereas Group 2 is suggested to be volcanic rock. Variation of K/Ti ratio and Eu anomaly of sediments supported the above results. In 2009, to elucidate the environment of sedimentation in the Scotia and Ross Seas in the Antarctic Ocean during the period from upper Pleistocene to the present, sediments from the seas were investigated by ^<57>Fe Mossbauer spectroscopy, instrumental neutron activation analysis and X-ray absorption near-edge structure. In Mossbauer spectra of Scotia Sea sediment, a specific doublet peak (isomer shifts of 0.57-0.59mms^<-1>, quadrupole splitting of 1.70-1.83mms^<-1>) was observed, suggesting the generation of primary glauconite by detailed speciation. In contrast, sediment cores from the Ross Sea and another sea area around Antarctica had no specific peak in Mossbauer spectra. Concentrations of iron and other elements in both sediments hardly fluctuated, that is, sedimentation matter in the Scotia Sea sediments containing iron species was not affected by the origin of specific iron species but by factors such as early-stage diagenesis.