n-Alkane Distribution and Their Palaeoenvironmental Implications in  Fluvial-Lacustrine Sediments in Dengkou, Inner Mongolia

To characterize the palaeoclimatic variations in monsoon margin zone, n-alkane analyses are done on samples co11ect- ed from one borehole of 15m in depth in Dengkou, Inner Mongolia. The results indicate that most samples are dominated by high carbon, primarily nC27 and nC2g , presenting a significant odd-carbon advantage and terrestria1 origin. Severa1 samples with a main peak of nC2.1 show the organic origin of partia1 aquatic plants. However, in the upper part of the borehole, short chain n- alkanes are relatively abundant, mainly with,1C18 as the main peak and without obvious odd-even predominance, reflecting the increased alga1 biomass. It is found that alternately cold and warm climatic conditions dominated the study area by various dis- tributions of n-alkanes in sediments, inline withlitho1ogy and organic carbon isotope variations in this study.