Susceptibility time series of the baoji section and the bearings on paleoclimatic periodicities in the last 2.5 Ma

Abstract

Magnetic Susceptibility measurements were conducted at 10 cm intervals in the Baoji section, a 160 m thick loess deposit in the southern Loess Plateau. An independent time scale was developed under control of paleomagnetic data by assuming that the eolian dust deposition rate during glacial periods is 1.5 times higher than that during interglacial periods. The 1600 susceptibility results were then plotted to the time scale which has a basal age of 2.5 Ma based on paleomagnetic measurements. Fourier analysis of the susceptibility time series shows strong spectral peaks centered at about 400,000, 100,000, 40,000 and 20,000 years, coinciding with the Milankovitch periods of paleoclimate. The dominant climatic periodicity recorded in the loess section appears as a function of the time interval considered: the 0–0.8 Ma interval is dominated by the period of about 100,000 years, the 0.8–1.6 Ma interval by 40,000 year cycles and the 1.6–2.5 Ma interval also by 100,000 year rhythms.