A new luminescence chronology for the Mangshan loess-palaeosol sequence on the southern bank of the Yellow River in Henan, central China

Abstract

An unusually thick loess-palaeosol sequence was found at Mangshan on the southern bank of the Yellow River, central China. Previous attempts to establish its chronology using TL and IRSL techniques have left major uncertainty over the stratigraphic division of the sequence. Here, we report results of a quartz and polymineral luminescence dating study on medium-grain (45–63 μm) fractions from the upper five loess units of the sequence. The base of the first loess unit is dated to 68.6 ± 4.9 ka with quartz extracts. While the quartz SAR age for the top of the second loess unit is 87.2 ± 6.1 ka, the application of an elevated temperature post-IR IRSL (pIR200IR290) SAR procedure to polymineral fraction from the same sample yields an age of 137 ± 10 ka. Using this procedure, the upper five loess units are dated. Our new luminescence dates show that the uppermost ∼41 m loess accumulated during the last glaciation. This disagrees with the previously published luminescence ages but is consistent with the proposed stratigraphy based on the correlation with sections in the Loess Plateau. The accumulation rates of the Mangshan loess during the last two climate cycles are found 4–7 times higher than those in the central Loess Plateau as well as those in the lower part of the sequence. Measurements of quartz OSL/TL sensitivity reveal significant differences among the samples in different loess units, hence providing evidence for the changes in the supply of source materials as a cause for the dramatic acceleration in loess accumulation.