中国西北干旱区湖泊沉积物中有机质碳同位素组成的环境意义——以民勤盆地三角城古湖泊为例  

THE PALEOENVIRONMENTAL SIGNIFICANCE OF ORGANIC CARBON ISOTOPE IN LACUSTRINE SEDIMENTS IN THE ARID CHINA: AN EXAMPLE FROM SANJIAOCHENG PALAEOLAKE IN MINQIN

作　　者：张成君[1] 陈发虎[1] 尚华明[1] 曹洁[1] 

机构地区：[1]兰州大学资源环境学院中德干旱环境联合研究中心,甘肃730000

出　　处：《第四纪研究》2004年第1期88-94,共7页Quaternary Sciences

基　　金：国家自然科学基金项目 (批准号 :40 0 410 0 4);国家重点基础研究发展规划项目 (批准号 :G19990 43 5 0 1);兰州大学博士留校科研启动基金项目资助

摘　　要：通过对中国西北干旱区石羊河流域民勤盆地三角城古湖泊沉积物有机质碳同位素组成 (δ1 3Corg)分析 ,表明末次冰期与全新世时气候和植被有明显的差异 ,末次冰期δ1 3Corg总体偏轻 (- 30‰～ - 2 5‰ ) ,而全新世碳同位素组成则有较大的变化 ,在早全新世碳同位素组成有多次短期快速变重 (- 1 0‰左右 )的变化 ,中全新世碳同位素组成总体偏重 (- 2 0‰～ - 1 0‰ ) ,晚全新世碳同位素组成偏轻 (- 2 5‰左右 )。分析表明湖泊沉积物有机质碳同位素组成反映了陆生C3植物和湖泊内源水生植物变化的关系 ,末次冰期以来西北干旱区C4 植物不发育 ,偏重的有机质碳同位素值与C4 植物无关。从沉积物中有机质组分、元素等分析表明 ,末次冰期时主要以河流相沉积为主 ,湖泊中有机质主要来源于上游祁连山的陆生C3植物 ,有机碳含量较低 ,表明当时的上游的陆生植被不繁盛 ,区域气候较干冷 ;从全新世开始 ,三角城古湖泊开始形成 ,沉积物中碳同位素组成偏重的有机质主要来源于湖泊中的沉水植物 ,此时湖泊水体较大 ,湖泊生产力较高。而沉积物中有机质碳同位素组成偏轻时期的有机质主要来源于挺水植物、陆生C3植物 ,较低的有机碳含量说明该时期陆生植被不发育 ,气候较干冷 。The organic carbon isotopic compositions ( δ 13 C org ) of Sanjiaocheng palaeolake in the Shiyang River drainage, Minqin Basin changed obviously from the Holocene to Last Glacial. δ 13 C org was lighter in the Last Glacial (-30‰～ -25‰ ) and it varied a lot in the Holocene. δ 13 C org became quickly heavier several times in the Early Holocene ( -10‰ ) and Middle Holocene (-20‰～-10‰), and lighter in the Late Holocene (ca -25‰). The organic components of sediments show that Sanjiaocheng section was a river environment in the Last Glacial, and organic matters with a low content in the sediments came mostly from the terrestrial C 3 plants. It’s made a conclusion that the vegetation was not overgrowth and the palaeoclimate was cold and dry. But from the Early Holocene, this area started to form a lake and organic matters in the sediments mainly came from submerged macrophytes, merged macrophytes and terrestrial C 3 plants. The heavier carbon isotopic compositions of organic sediments came mainly from the submerged macrophytes and the lake level was higher during this time, and accompanied by a high lake productivity. The lighter carbon isotopic compositions of organic sediments came mainly from the emergent macrophytes and terrestrial C 3 plants and the level was lower. Because there was a low organic carbon content, it showed that the vegetation was bad and the palaeoclimate was cold and dry.

关 键 词：有机质碳同位素组成 沉水植物陆生植物 三角城 区湖泊沉积物 

分 类 号：P736.41[天文地球—海洋地质] P512.2[天文地球—海洋科学]