Weathering and pedogenesis of the late Pleistocene and Holocene aeolian loess-paleosol sections in the Yellow River source area, NE Tibetan Plateau

Abstract

The aeolian loess-paleosol sections on the northeast Tibetan Plateau (NETP) are a valuable source of paleoclimatic information because of their geographical location. In this study, two late Pleistocene–Holocene aeolian loess-paleosol sections were identified based on detailed field investigations in the Maqu reach in the Yellow River source area on the NETP. A robust chronostratigraphic framework for these two sections was established using AMS 14C dating, optically stimulated luminescence (OSL) dating, Bacon age-depth modelling and stratigraphic correlation. Measurements of magnetic susceptibility, hygroscopic water, loss-on-ignition, grain-size, micromorphology, and chemical element analysis suggest that most stratigraphic units in these aeolian loess-paleosol sections are in weak weathering and pedogenesis, whereas the mid-Holocene paleosol approaches to the moderate weathering and pedogenesis, and the sediments are in initial weathering stage of Na+ and Ca2+ leaching is dominated by plagioclase weathering. The main pedogenesis in the mid-Holocene paleosol is calcification process. In terms of intensity of weathering and pedogenesis, the stratigraphic units can be ordered as follows: paleosol > modern soil > transitional loess > aeolian loess. Multi-index comparison shows that the local climatic evolution during the late Pleistocene–Holocene was closely related to the evolution of the East Asian summer monsoon (EASM) and the Westerlies. Overall, the results provide a foundation for further exploration of the pedogenic and paleoclimatic evolution on the NETP.