【摘要】 对我国河西走廊东端西北内陆干旱区与东部季风区交汇带的石羊河流域三角城古湖泊剖面进行了有机质碳同位素组成、有机碳和碳酸盐含量分析 ,重建了西北干旱区全新世古气候高分辨变化模式。分析结果表明有机质碳同位素组成能灵敏地反映该区湖相地层记录的古气候特征 ,是一个较好的古气候替代指标。在温湿期 ,湖泊水体扩大 ,生产力高 ,沉积物中有机质主要是沉水植物供给 ,δ1 3Corg偏重 ;在干冷期 ,湖泊水体减小 ,沉积物中有机质以挺水植物为主 ,植被不发育 ,沉积物中有机质含量低 ,δ1 3Corg偏轻。全新世气候演化主要分为 4个主要阶段 :暖湿期(约 10 0 0 0～ 5 0 0 0 a B.P.)、温湿期 (约 5 0 0 0～ 3 80 0 a B.P.)、凉湿期 (约 3 80 0～ 2 6 0 0 a B.P.)、干旱期 (约 2 6 0 0 a B.P.至今 ) ,各阶段中气候快速变化明显。该区的古气候演化与同处于我国东部季风西北边缘的相邻地区有一定的可比性 ,也具有自身的区域特色。更多还原

【Abstract】 In this paper,we analyses the carbon isotopic compositions of organic matters,organic carbon and carbonate concentration of the Sanjiaocheng palaeolake sediment section in the intersection belt of northwestern dry inland and eastern monsoon areas of China.Holocene high resolution palaeoclimatic variation is reconstructed in the northwestern arid semiarid areas by using δ 13 C org proxy.Its obvious in the northwestern arid semiarid China that δ 13 C org has a great range of values,and during the warm and wet climate,δ 13 C org (-10‰～-20‰)is much heavier than that during the dry and cold climate(-25‰ or so).In the arid semiarid areas,organic matters in the lake sediments have different sources.During warm and wet climate,the lake water enlarges and high submerged macrophytes have a high productivity and serve as the source of organic matters and thus δ 13 C org is heavier,while during dry and cold climate,the lake shrinks with vegetation growing poorly,organic matters in the lake sediments deriving from the submerged macrophytes become lower in the concentration of organic carbon,and thus δ 13 C org is lighter.By analyzing δ 13 C org in the Sanjiaocheng lake section,we find that Holocene climate in the northwestern arid semiarid China is the background of dryness and coldness,but there are many abrupt and short periodic warm and moist events.In the whole,Holocene climatic variation in the arid semiarid China can be divided into 4 main stages:warm wet period (about 10 000～5 000 aB.P.),temperate wet period (about 5 000～3 800 aB.P.),cold wet period (about 3 800～2 600 aB.P.),and dry period(from about 2 600 aB.P.).In each stage,the climate changes rapidly and apparently.The palaeoclimate with self characteristics in this area is the same as that in the adjacent areas,which belong to the northwestern edge of eastern monsoon.更多还原