EVOLUTION OF AEOLIAN ACTIVITIES IN THE TENNGER DESERT DURING THE HOLOCENE:COMPREHENSIVE RESEARCH BASED ON GEOLOGICAL RECORDS AND SIMULATED DATA
The Tengger Desert(37°24′～40°1′N,102°45′～105°37′E)is located not only in the transitional zone between arid and semi-arid regions but also in the margin of the modern East Asian monsoon domain.The variation of the East Asian monsoon on the spatiotemporal scale is commonly regarded as one of the essential exterior forces driving the alternating expansion and shrinkage of the Tengger Desert.To reconstruct the evolution of the paleoenvironment and aeolian activity,loess,lacustrine sediments,pollen,and alluvial sediments in the margin of the Tengger Desert were widely used.However,there are few geological records in the hinterland of the desert.Additionally,geological information recorded by stratigraphic sequence at different locations in the Tengger Desert has regional limitations.In this study,4 profiles(TGL-A(37°03′8″N,103°21′07″E;2.6m),TGL-B(37°51′33″N,103°23′49″E;2.5m),TGL-C(37°39′16″N,103°10′59″E;2.6m),and TGL-D(37°36′46″N,103°36′45″E;2.0m))in the southwestern of the Tengger Desert were studied,and 11 optically stimulated luminescence(OSL)samples were collected and measured.Then,we collect the OSL age of 69 aeolian sediments and the 14C age of 137 paleosol,lacustrine sediments and calcareous root canals since ca.14 ka.Moreover,in order to reduce the uncertainty of using stratigraphic sequence to reconstruct the paleoenvironmental evolution of the Tengger desert,the TraCE-21 ka(Transient Climate Evolution Simulation over Last 21000 Years)paleoclimate simulation data was also used to calculate the effective moisture and dune mobility index in the warm season(JJASON)and cold season(DJFMAM).The evolution and driving factors of aeolian activity in the Tengger Desert during the Holocene are discussed comprehensively.The results indicate as following:(1)During the Early Holocene(11.7～8.0 ka),the coarser mean grain size and a larger number of aeolian sediment OSL ages indicated that the aeolian activity was strong.The simulation results suggest that the aeolian activity appeared a weakening trend in this period,which is mainly due to the decrease of near-surface wind speed caused by the weakening East Asian winter monsoon,then resulting in a large amount of aeolian accumulation.(2)During the Middle Holocene(8～3 ka),the higher low-frequency magnetic susceptibility and more 14C age indicated the development of paleosol,the improvement of effective moisture,and the weakening of aeolian activity.The simulation results show that the effective moisture was relatively high,and the aeolian activity was weak in this period.The enhanced East Asian summer monsoon(EASM)brought more rainfall,which increased the effective moisture and stabilized the dunes.(3)During the Late Holocene(3～0 ka),the coarser mean grain size and the increasing number of aeolian sediment OSL ages implied that aeolian activity was reactive.The simulation results show that the aeolian activity displayed an increasing trend.The weakening of EASM and the drying of the Tengger desert induced the effective moisture gradually decreased,vegetation degraded,and fixed dunes reactivated.
万方数据
维普
