Asynchronous variations of East Asian summer monsoon, vegetation and soil formation at Yulin (North China) in the Holocene

Abstract

ABSTRACTIn the East Asian monsoon region, Chinese speleothem δ18O records exhibit a maximum monsoon strength during the early Holocene. However, other proxy data from lakes or loess, interpreted as monsoon rainfall, show a mid‐Holocene monsoon optimum. This discrepancy may come from specific climate interpretation of different proxies. Here we report multiproxy records from a single loess–palaeosol sequence at Yulin in the monsoon marginal northern China, based on an independent and high‐precision chronology. Our long‐chain n‐alkane δD values, together with related biomarker proxies including the average chain length and concentration of long‐chain n‐alkanes, reveal a weakening trend in monsoon strength and less woody vegetation since ~6 ka. However, other soil formation‐related proxies, such as magnetic susceptibility, grain‐size distribution and total organic carbon, show a decreasing trend since 4–3 ka. We find that monsoon and vegetation are controlled by insolation variation, while soil formation is more related to temperature and humidity changes. Our multiple proxy comparison reveals different controlling mechanisms leading to different interpretations in monsoon, vegetation and soil formation reconstructions. This finding suggests that previous debates on Holocene monsoon changes in East Asia probably stem from the specific proxy interpretation.