DISTRIBUTION OF N-ALKANES AS INDICATORS OF PALEOVEGETATION CHANGE IN ANCIENT CULTURAL LAYERS OF JINLUOJIA SITE IN MACHENG, HUBEI PROVINCE

Using GC/MS analysis, a series of lipids, including n-alkanes, n-alkanoic acids, n-alkanols and n-alkan-2-ones, have been identified from the sediments of Jinluojia archaeological site profile(ancient cultural layers) in Macheng, Hubei Province. Pioneering work of lipids applied to the archaeology was mainly focused on elucidating the diet of ancient human and agricultural development but the retrieval of the vegetation even climate change around archaeological sites were rarely discussed. This paper mainly discusses n-alkanes in this profile, showing the distinct n-alkane distributions in different cultural layers. C31 or C29 dominates in the upper layers but C17 gradually replaces the principal peak position down the profile with the bimodal distribution of C17 and C31 in the intermediate layers, suggesting that n-alkanes in this profile have a mixed origin and are mainly derived from microorganisms and higher plants. The indices of C₂₇/C₃₁ and ACL (average chain length) of n-alkanes reveal relative abundance of woody plants to grassy plants, presumably related to the climate change. Multiple-staged changes of δ¹³C_org value display in the profile, reflecting the relative variations of C3 and C4 plants around archaeological sites during the past ca. 3 000 a. Significantly, the variations of n-alkanes indices probably provide plentiful information about the climatic change and ancient human activities besides the microbial reworking, vegetation change and pedogenesis. However, further and more detailed work should be done for our better understanding the ancient civilization of Macheng region.