Author:LIU Qiang1,GU Zhao—yan1,LIU Jia—qi1,YoU Hal—tao1,2,LU Hou-yuan1,CHU Guo—qiang1,QIXiang—lei3,Negendank J(o)rg F W4,Mingram Jens4,Schettler Georg4

(1.Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China；2.College of Geosciences,Jilin University,Changchun 130061,China；3.Geological Publishing House,Beijing 100083,China；4.GeoForschungs Zentrum Potsdam,Potsdam 14473,Germany)

Key words:carbon isotope of bulk organic matter；paleoclimate and paleoenvironment；virtual precipitation; dryness; Huguangyan Maar Lake

Abstract:

Core HUG—B of Huguangyan Maar Lake recorded paleoclimatic and paleoenvironmental changes since 62 kaBP. Bulk organic carbon isotopic composition (δ13Croc)of HUG-B core is analyzed. The variation range of δ13Croc values is from 一28.5‰ to一15.5‰. Combined with pollen and organic geochemistry results, the δ13Croc curve of Huguangyan Maar Lakes since 62 kaBP can be divided into six stages.During 62~ 58 and 48～40.5 kaBP,the δ13Croc values were much more negative,the organic components of sediments were mainly from terrestrial C3 plants of tropical and subtropical forest, indicating two warm and humid periods.In contrast,during 58～48 and 40.5～17.2 kaBP, the paleoclimatic conditions became much drier and colder, with significantly heavier δ13Croc values. The organic components of these two periods were of dominant C4 herbaceous plants,suggesting that the open grassland landscape dominated in the lake shore of Huguangyan Maar Lake when the lake level dropped because of serious dryness around Huguangyan Maar Lake area.Since 17.2kaBP,there is the tendency of gradual lighter δ13Croc values in spite of much high frequency oscillations,which indicates the tendency to warmer and more humid condition superimposed by many alternations of warm, humid condition with cold and dry climate. After 4 kaBP, δ13Croc values became heavier,which may indicate increased drought,but it is most likely the distortion caused by human activity. Based on comprehensive analysis,the virtual precipitation (i.e. precipitation minus evaporation) is the key factor that controls the C3／C4 relative plants biomass around Huguangyan area.This result supports the fact that regional climate change rather than atmospheric CO2 acted as the dominant control factor on glacial—interglacial variations in C3 and C4 plant relative abundance in tropical low latitude area such as around Huguangyan Maar Lake.

62kaBP以来湖光岩玛珥湖沉积物有机碳同位素记录及古气候环境意义