The onset of extensive loess deposition around the G/M boundary in China and its palaeoclimatic implications

In northern China the Red Clay-loess contact is palaeomagnetically defined at about the Gauss/Matuyama boundary. The Red Clay formation has recently been proposed as mostly of wind-blown origin, and can be interpreted as having been formed under climatic conditions of continuous warmth punctuated by small-amplitude oscillations. The shift from Red Clay development to extensive loess deposition exhibits a 3-fold abrupt increase in aeolian dust deposition rate, and marks the beginning of frequent and chaotic climatic fluctuations. This event implies a large-scale reorganization of the atmospheric circulation over East Asia, in particular the northward shift and intensification of the Siberian High, which may have resulted from a dramatic uplift of the Tibetan Plateau. Compared to another climatic shift recorded by the Chinese loess deposits, which occurred at about the upper boundary of the Olduvai subchron, the Red Clay-loess shift is much more pronounced and recognizable in the field. It appears that, in regional stratigraphic studies, the G/M magnetic reversal has a better correlation potential than the upper Olduvai. (C) 1997 INQUA/Elsevier Science Ltd.