Late Pleistocene to present landscape and anthropomorphic change in the Keerqin (Horqin) Sandy Land, China: Insights from sedimentary records

The current distribution of dune fields and sandy lands in northeastern China is closely related to the hydrological environment with fluvial processes often providing sediments for dune formation. The Keerqin Sandy Land (also known as Horqin) incised by the tributaries of the West Liao River and located at the northern boundary of East Asian summer monsoon (EAM) in northeastern China, is sensitive to monsoon system variability. As such, aeolian-fluvial-paleosol sequences in northeastern China are valuable geological archives for reconstructing river system behavior and palaeoclimate since the Late Quaternary. Here we show from analysis of these archives that fluvial systems were active at ∼11 ka likely due to the occurrence of floods at the end of the last glaciation. This was followed by frequent channel migration within the floodplains around 7∼5 ka associated with mid-Holocene monsoon precipitation fluctuation and higher humidity. Sediments from this active Holocene fluvial system along with a more humid climate produced conditions in the Keerqin Sandy Land that resulted in extensive paleosol formation. These findings are consistent with the timing and development of paleosols in other sandy lands in northeastern China. Former channels and floodplains along with a higher groundwater table aided the early development of agriculture in this region: many of the former flood plains are still intensively cultivated and highly productive.