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Paleoclimatic Interpretation of a Loess-Paleosol Section in China Based on Mineral Magnetic Properties and on Calcium Carbonate Distribution
Michael SINGER, Dept. of Land, Air and Water Resources, Univ. of Calif., Davis CA 95616 USA
Kenneth VEROSUB, Dept. of Geology. Univ. of Calif., Davis, CA 95616, USA
Jeff LIGHT. Dept. of Geology, Univ. of Calif., Davis, CA 95616, USA
Xiaolin ZHAO. State Seismological Bureau. Beijing, PRC
Paleosols S1 to S5 and their loess counterparts were sampled at 10 to 20 cm vertical in a new loess/paleosol section north of Potou near the city of Fuxian, Shanxi Province, PRC. Mineral magnetic properties including magnetic susceptibility before and after citrate-bicarbonate-dithionite (CBD) extraction and soil chemical properties such as calcium carbonate content were determined for the samples. As with other nearby sections, the magnetic susceptibility was highest in the paleosols, and lowest in the loess. In addition, the carbonate was highest in the loess and lowest in the paleosols. The low frequency magnetic susceptibility in the paleosols had maximum values of 137 to 290 x 10-8m3kg-1, while the corresponding values in the loess varied from 24 to 45 x 10-8m3kg-1. CBD extraction informed lowered the susceptibility of the paleosols to about the same level at the loess. Carbonate values exceeded 10% in the loess and were less than 3% in most of the soil samples. The pre-CBD magnetic susceptibility values were used to identify samples that could be considered as "unweathered" loess and as "strongly weathered" paleosols to determine if carbonate leaching models, such as those reviewed by Retallack (1994) could be used to quantify precipitation during the soil forming intervals represented by paleosols S1 to S5. The situation is complicated by multiple episodes of pedogenesis and by the overlapping nature of the signal. Submitted to Symposium 54 - Loess and Paleoclimate.
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