Forcing mechanisms of paleosol development at the edge of East Asian Summer Monsoon area over the past 20 kyrs: A large-scale analysis of lacustrine and dune field sedimentary archives in Central China

Abstract

Extensive paleosols have intermittently developed across the East Asian Summer Monsoon (EASM) region over the past 20kyrs but climate forcing mechanisms remain uncertain. In this paper, we compile 593 absolute ages of 87 aeolian sand-paleosol profiles from the Hulun Buir (HB), Otindag (OD) and Qinghai Lake (QH) dune field of central China to more accurately understand paleosol development across this region. In addition, paleoclimatic records from Hulun Lake, Dali Lake and Qinghai Lake from within the dune field are quantitatively analyzed to understand the main drivers of paleosol development. Results show that effective moisture was the pacemaker of paleosol development in the OD dune field with peak deveiopment of paleosols in the mid-Holocene (8–3.5 ka). The HB dune field also extensively developed paleosols during the mid-Holocene optimum (9–4 ka), corresponding to strong effective moisture and high lake-level in the Hulun Lake record. Paleosols were widely developed in the QH dune field during the middle to Late Holocene (6–1 ka), which was not correlated with the precipitation and temperature records of the Qinghai Lake alone, but was in phase with the effective moisture records (i.e., high lake-level and Thaumarchaeol content). These results confirm that effective moisture is the main forcing mechanism of paleosol development at the edge of the EASM region. This explains the delay of the mid-Holocene optimum compared to the early Holocene insolation peak, because the increased evaporation caused by the increase in insolation and temperature in the early Holocene may have been sufficient to reduce the effective moisture, resulting in increased regional aeolian activity and dust availability. We also suggest that the correlation between magnetic susceptibility and precipitation in the dune fields in northern China is not a simple linear relationship, but a potential proxy for regional effective moisture. This study is important for understanding the mechanism of paleosol development and related climate dynamic feedbacks in arid and semi-arid regions, as well as for combating land desertification.