Abstracts of Symposium 55 and some papers from other related Symposia.

A Pleistocene Climatic Record on the Basis of a Complete Loess-Paleosol Sequence in Central China

Paul HAESAERTS, IRSNB-KBIN, rue Vautier 29, B-1040 Bruxelles, Belgium
Josef HUS, KMI-IRM, B-5670 Dourbes, Belgium
Jiansheng SHI, INEG, 050803, Zhengding, Hebei, P.R.China
Hongping ZHANG, INEG, 050803, Zhengding, Hebei, P.R.China
Bater BAI, Academia Sinica, P.O.Box 9825, Beijing 100029, P/R/China
Roland PAEPE, BGD-SBG, Jennerstraat 13, B-1040 Brussel, Belgium

A complete climatic signal in the loess plateau of Central China was obtained by combining the loess-paleosol record from soil unit S0 until S15 of the Huangling section with that from unit S9 until loess unit L36 of the Jiacun section near Baoji. The Huangling section displays one of the most complete loess-paleosol archives for about the last 1,3 MY, while in the Jiacun section paleosols in the timespan from about 1,3 MY until about 2,5 MY could be remarkably well differentiated and described for a first time, in one single, continuos, vertical outcrop of easy access. At least 35 first order paleosols could be recognised for the Pleistocene. Paleopedologic analysis provided a high resolution climatic record which showed a one to one correspondance with the astronomically tuned planctonic and benthonic oxygen isotope data of ODP677 in the Eastern Pacific. This suggests that the climatic signal retrieved from the soil-paleosol sequence in Central China reflects global long term climatic changes. A polarity magnetostratigraphy of both sections yielded the time markers needed. Besides the most important Quatemary geomagnetic field reversal boundaries, also a "Brunhes-Matuyama Precursor" was found in loess until L9. The paleosols are characterized by an authigenically produced fine-grained "magnetites". The variance of the magnetic susceptibility signature of the complete sequence, with a resolution of 10 cm in depth, resembles well the oxygen isotope record of ODP677 but it exact link with climate remains unsolved. This rock magnetic parameter, which reflects the magnetic contents, has proven to be very useful for correlation of sections in the loess plateau and showed to be a good indicator of soil development, as was evidenced in loess unit L9. An analysis in detail of soil unit S5 in a road cut section, where it was well exposed; demonstrated that the maximum susceptibility occurs in the Bh horizon of the upper soil of this soil complex. Analytical data obtained from the complete sequence include also CaCO₃ and organic matter content, as well as grain size, carbon and oxygen isotope analysis. To conclude, macro- and micro- pedologic analysis resulted in a high resolution unique continental record of climatic changes for about the last 2,5 My in Central China. The high variability of the climate and the dominance of a 100 KY quasi-periodicity, especially during the Brunhes chron, preceeded by less variability, points clearly to non-linear behaviour.

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