湖北麻城金罗家遗址古文化层的正构烷烃分布及其古植被意义

利用气相色谱-质谱联用仪(GC-MS)对湖北麻城金罗家遗址古文化层样品进行了系统分析,检测出丰富的类脂物分子,包括正构烷烃、一元正脂肪酸、一元正脂肪醇和α-正构脂肪酮等,主要讨论正构烷烃类脂物的分布特征。正构烷烃的分布在各文化层不同,其中,在生土层以C17为主峰;西周文化层F2和F4两样品以C17和C31为双主峰,F3样品以C17为主峰;东周文化层主要以C17和C31为双主峰,而F 7以C31为主峰,F9以C17为主峰;唐宋文化层以C17和C31为双主峰;明清文化层以C31为主峰,现代耕植土层以C29为主峰。而正构烷烃高碳数C27/C31比值的变化反映出遗址域中木本植物与草本植物的相对变化,正构烷烃高碳数ACL值反映遗址域中的草本植物与木本植物之间的转变,有机δ13C表现为C3和C4植物,它们在本剖面上表现出多阶段的变化。因此,正构烷烃在不同的人类古文化层具有不同的分布特征,除了反映当时的微生物活动、植物属种的相互取代或分子沉积后的改造作用外,还可能蕴藏着当时的气候变化和古人类活动的信息,有待进一步研究。

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 δ13Corg 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.