MILLENNIUM SCALE CLIMATE ABRUPT EVENTS RECORDED IN THE HOLOCENE LOESS OF THE YUNCHENG BASIN
Identifying the evolutionary history and dynamics of the East Asian monsoon during the Holocene is important for predicting future global climate change.Paleoclimate studies have shown that the Holocene climate experienced a series of abrupt climate change events on a centennial to millennial scale,however it is still controversial whether the loess in China has the potential to record rapid climate change in the Holocene.In this study,the loess section(110°59′33″～111°37′29″E,35°09′38″～35°34′11″N)in Wenxi County,Yuncheng City,Shanxi Province,China was selected for Holocene hydroclimate reconstruction.The entire section was a compact and blackish Holocene paleosol layer S0,with a thickness of 6 m.After removing the weathered soil on the top surface,300 bulk samples were collected at 2 cm intervals and six optically stimulated luminescence(OSL)samples were collected at 1 m intervals.Those OSL ages were incorporated into a Bayesian age-depth model using Bacon software to establish the chronology,which ranges from 11.98～1.68 ka B.P.In this study,we investigated the Wenxi sequences from the southeastern Chinese Loess Plateau,using multi-parameter rock magnetic investigation(such as magnetic susceptibility,temperature-dependent magnetic susceptibility(x-T),magnetic hysteresis loops,First-Order-Reversal-Curve(FORC),temperature-dependent isothermal remanent magnetization(IRM),low-temperature cycling of room temperature induced SIRM)and geochemical elements to reveal the evolution of East Asian summer monsoon precipitation and its response to abrupt global climate events since 11.98kaB.P.in this region.Our results indicate that the main magnetite-bearing minerals are magnetite and maghemite.The particle sizes of the magnetic particles are dominated by single-domain(SD)and pseudo-single-domain(PSD)particles,with a small amount of multi-domain(MD)particles.Results of geochemical elements indicate that the distribution of Ca,Ti,Mn,Fe,Rb and Sr is different,among which Ca and Sr are most significantly affected by pedogenesis.Except Ca and Sr,which are significantly negatively correlated with the magnetic susceptibility,the other trace elements and Rb/Sr ratio are significantly positively correlated with the magnetic susceptibility,which indicates that the content of trace elements in Wenxi section can well reflect the climate and environmental changes during the Holocene.The consistent changes of the magnetic susceptibility and the Rb/Sr ratio mainly reflect the changes of the pedogenesis controlled by the East Asian summer monsoon.We also found that the regional monsoon precipitation increased between 11.98 ka B.P.and 9.4 ka B.P,and decreased after 9.4 ka B.P.,with a peak at 9.4 ka B.P.In addition,high-resolution magnetic susceptibility records reveal that there are four significant abrupt climate change events at 4 ka B.P.,6 ka B.P.,8 ka B.P.and 9 ka B.P.,which agrees with the Bond cold events.This may reflect that the abrupt climate change in the high latitudes of the Northern Hemisphere has a significant impact on the monsoon precipitation in Yuncheng Basin.
万方数据
维普
