THE OCCURRENCE AND ENVIRONMENTAL SIGNIFICANCE OF BRANCHED GLYCEROL MONOALKYL GLYCEROL TETRAETHERS IN LOESS DEPOSITS FROM SANYUAN COUNTY,XIANYANG CITY,SHAANXI PROVINCE IN THE SOUTH-CENTRAL PART OF THE CHINESE LOESS PLATEAU
Glycerol Dialkyl Glycerol Tetraethers(GDGTs)derived from archaea and bacteria are important indicators for reconstructing paleoenvironment.In recent years,Glycerol Monoalkyl Glycerol Tetraethers(GMGTs,or H-GDGTs)have been detected in cultured archaea,oceans,rivers,lakes and peat.The presence of branched Glycerol Monoalkyl Glycerol Tetraethers(brGMGTs,or H-brGDGTs)is thought to be associated with high-temperature environments.At present,the distribution characteristics and environmental significance of brGMGTs in loess remain unclear.The Sanyuan loess section(34.70° N,109.04°E)is located in the south-central part of the Chinese Loess Plateau,with a depth of 17.1 m and an age span of 0 to 219 ka,covering strata units such as S0,L1,S1,L2,and S2-1.The Sanyuan Loess section has good stratigraphic continuity and high resolution,which is an ideal material for brGMGTs research.In this study,72 loess and paleosols samples from the Sanyuan loess section were analyzed.Using high performance liquid chromatography atmospheric pressure chemical ionization tandem mass spectrometry,brGMGT-1020,brGMGT-1034,and brGMGT-1048 were identified in the Chinese Loess Plateau.The relative content of brGMGTs was correlated with that of Ⅰa,Ⅱa and Ⅲa,indicating that brGMGT-1020,brGMGT-1034 and brGMGT-1048 may be transformed from Ⅰa,Ⅱa and Ⅲa,respectively,under microbial influence.The relative content of brGMGTs in the Sanyuan loess section was positively correlated with depth or age,which may be caused by the physical and chemical processes after deposition.In loess and paleosols samples with deposition age less than 40 ka,the fluctuation trend of brGMGTs relative content can partly reflect climatic and environmental characteristics,i.e.,higher brGMGTs relative content may indicate warmer climatic conditions.Therefore,brGMGTs provide a new potential biomarker for identifying past warming events.
Chinese loessbranched glycerol monoalkyl glycerol tetraethers(brGMGTs or H-brGDGTs)biomarkers
万方数据
维普
