Tectonic Forcing of the Extreme Aridification of the East Asian Interior at Around 900 ka–Insights From the Spatially Inconsistent Magnetization of Chinese Loess

Abstract

The upper sandy loess unit L9 on the Chinese Loess Plateau (CLP) corresponds to marine isotope stages 22–24, and it represents aeolian deposition under conditions of extreme aridification. However, the forcing mechanism remains controversial. Numerous paleomagnetic studies in the eastern CLP show that the coarsest part of L9 is remagnetized and has a normal geomagnetic polarity. However, our results show that in loess sections in the western CLP the coarsest part of L9 records a primary reverse polarity. This spatially inconsistent magnetization pattern originates mainly from the different magnetic carriers of the characteristic remanent magnetization (hematite in the western CLP and magnetite in the eastern CLP), which suggests a different dust provenance between the western and eastern CLP. We ascribe this spatial contrast in dust provenance to the episodic uplift of the northeastern Tibetan Plateau, which also led to the extreme aridification of the East Asian interior at ∼900 ka.