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

Evidence for Abrupt Climate Change from the Magnetic Susceptibility Record of a New Loess/Paleosol Section in China

Jeff TENPAS, Dept. of Land Air and Water Resources, Univ. of Calif., Davis CA 956I6 USA.
Kenneth L. VEROSUB, Dept. of Geology, Univ. of Calif., Davis, CA 956I6 USA,
Robert H. SHUMWAY, Div. of Statistics Univ. of Calif., Davis. CA 95616 USA,
Michael J. SINGER, Dept. of Land, Air and Water Resources. Univ. of Calif., Davis CA, 956I6 USA,
Xiaolin ZHAO, State Seismological Bureau. Beijing. PRC.

Magnetic susceptibility curves are a primary source of information about the paleoclimate record of the Chinese loess plateau. Recent results have shown that pedogenesis is the major cause of variations in the magnetic susceptibility record. This result implies that at any level in the section. the magnetic susceptibility value represents the accumulated enhancement that has occurred over the entire time interval that the level was within the zone of active pedogenesis. In the language of signal theory, the magnetic susceptibility record is the convolution of the original paleoclimate signal with a pedogenic transfer function. We used a CBD- extraction procedure and measurements of mineral magnetic parameters to isolate the pedogenic component of the magnetic susceptibility signal. We then used deconvolution procedures which we developed to recover the underlying climate signal. For a new loess section at Jiaodao. we find that over the time interval 40 to 700 ka BP, the climate appears to have changed much more rapidly and to have shown greater variability than we would have inferred from the magnetic susceptibility curves alone. In some cases. rapid climate change in one direction is punctuated by short- term change in the opposite direction. Our results imply that abrupt changes in climate may he a persistent characteristic of the climate system.

Submitted to Symposium 55 - Climatic Implications of Paleosols

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