Abstract: For its characteristic high-resolution the eolian Manshan loess is exposed along the south bank of Huanghe River,situated on the northwest suburbs of Zhengzhou City,Henan Province,which is wholly composed of loess strata,over 160 m thick,upward from loess L₁₅ or paleosol WS₁.The loess sequence in this area are perfect and the typical loess profiles are exposed in Taohuayu and Zhaoxiayu,in which the strata upward from paleosol S₂ at Taohuayu profile have been preliminary studied.According to the lithology,susceptibility,TL and ¹⁴C dating,the stratigraphical units have been subdivided into S₀,L₁,S₁,L₂ and S₂ with 0.6m,70.8m,9.9m,12.4m and 1.0m thick respectively.It is of great significance that there exist quite a thickness of Malan Loess (L₁) formed in the Late Pleistocene.
We have sampled at an interval of 10cm and measured the profile magnetic susceptibility in the field and mass magnetic susceptibility in the laboratory respectively.The values of magnetic susceptibility of the Mangshan Loess is smaller than that inside the Loess Plateau.We have correlated the magnetic susceptibility profile with the SPECMAP marine oxygen isotope time series and inferred that the rapid changes in susceptibility values at the L₁/S₀,S₁/L₁ stratigraphic boundaries correspond with the oxygen isotope stage 2/1 (12.05ka) and 5/4(73.91ka) transitions respectively.With the two marked points,by using the Kukla's susceptibility age model to calculate the age of successive stratigraphic levels we then derived a chronology.Grain size of the loess during the last glaciation (L₁) was analyzed at an interval of 40cm,and depositional rate of each unit has also been calculated.
The susceptibility of Chinese loess mainly manifests the prosperity or decline of the southerly summer monsoon from the low latitude ocean,so the susceptibility values may be used as a proxy index for the change strength of summer monsoon climate.Average deposit rate and resolution in late Pleistocene loess at Mangshan reveal a great difference of dust deposit blown and entrained by the northerly winter monsoon from the high latitudes area between glaciation and interglaciation or stadial and interstadial.The maximum mean deposit rate is up to 2.47mm/a during the last glaciation,whereas the minimum is 0.18mm/a yet during the last interglaciation.The frequency and amplitude of winter monsoon variations revealed by the grain size record whose mean resolution come to 40.5 a/10cm dring the last stadial in the last glaciation at Mangshan are more detailed than that by the Greenland ice core.
The late Pleistocene loess strata in Mangshan are both related to and different from that inside the Loess Plateau.For its high-resolution the Mangshan loess during last glaciation can reflect the abrupt climate changes of East Asian monsoon,and is a excellent record for the Past Global Changes study on high-resolution and short timescale.