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The Mangshan loess plateau is located 25 kin to the west of Zhengzhou on the south bank of the Yellow River. Here the river flows out through the Sanmen Gorge releasing most of its suspended load following a dramatic decrease in gradient. The stratigraphy of the Mangshan loess deposits, consisting of a number of loess and palaeosol sequences, was established following magnetostratigraphic studies and measurements of magnetic susceptibility and grain size distribution. The Bruhnes/Matuyama boundary was found at the depth of about 130 in, indicating that this sequence at Mangshan resembles what is observed elsewhere in the Loess Plateau.

The upper part of the Mangshan loess displays extremely high sedimentation rates (similar to 50 m(3) per 1000 years), lower susceptibility values and coarser grain-size distribution, unlike the lower part of the profile and other sections in the Loess Plateau. This striking change indicates that the upper Mangshan loess had a different sediment source, different from the deserts that act as a common source for most of the loess deposits in central China. This sediment source is believed to be the proximal Yellow River floodplain, and the ancient alluvial fan lying at the eastern end of the Sanmen Gorge. The age estimation of the formation of the alluvial fan, based on Mangshan loess, suggests that the Yellow River may have eroded the Sanmen Gorge at approximately MIS 7. (c) 2006 Elsevier B.V. All rights reserved.