中亚哈萨克斯坦西部过去～30000年以来有机碳同位素变化及其意义

选取位于中亚干旱区哈萨克斯坦中西部的VA剖面作为研究对象,在AMS14C测年基础上,分析了该剖面记录的过去～30000年以来的有机碳同位素组成变化。结果表明:该剖面记录的过去～30000年以来有机质碳同位素值(δ13Corg)变化于-26.19‰--22.12‰之间,均值为-23.77‰,植被主要为C3植物,C4植物仅仅在末次冰盛期出现且其相对丰度极低。因此VA剖面土壤有机碳同位素组成变化主要反映的是C3植物对气候环境因子的响应,进一步对影响该地区植物碳同位素因素的分析发现,降水是控制该地区C3植物碳同位素变化的主要因素,即:降水增多导致C3植物碳同位素值偏负,可以用来指示研究区古降水变化趋势,CO2浓度以及温度仅仅在末次冰盛期对C3和C4植物相对丰度有一定的影响。

The organic carbon isotope variation and its paleoclimate indicator in Western Kazakhstan during past 30000 years

This research focused on a loess section(VA section) in Western Kazakhstan to study the organic carbon isotope(δ13Corg) variation during past -30000 yr BP basing on AMS 14C dates.The results indicated that δ13Corg in VA section varied between-26.19‰ and-22.12‰ and the average value is-23.77‰.At most time of past 30000 years,the vegetation was major C3 plants and the C4 plants was only present during last glacial maximum and the relatively abundance was very low.Further analysis indicated that the precipitation was the major control factor on carbon isotope values of the C3 plants,that is the more precipitation lead more negative δ13Corg in C3 plant.The temperature and atmosphere CO2 concentration were only play a light role in relatively abundance of C3 and C4 plants during last glacial maximum.