湖泊沉积物色度在短尺度古气候研究中的应用  

SIGNIFICANCE OF LAKE SEDIMENT COLOR FOR SHORT TIME SCALE CLIMATE VARIATION

作　　者：吴艳宏[1] 李世杰[1] 

机构地区：[1]中国科学院南京地理与湖泊研究所,江苏南京210008

出　　处：《地球科学进展》2004年第5期789-792,共4页Advances in Earth Science

基　　金：国家自然科学基金项目"青藏高原半混合型湖泊沉积过程与湖泊环境纹泥记录"(编号:40071001)资助

摘　　要：在ODP对大西洋海洋沉积物的研究中,色度作为最直观和简便的指标被普遍用于反映千年尺度的气候环境变化。能否用湖泊沉积物色度反映短时间尺度的气候环境变化?利用CIE/L a b 表色系,通过青藏高原可可西里苟仁错湖泊沉积物的L 、a 和b 值与有关地球化学指标的统计相关关系分析,对湖泊色度指标在短尺度古气候研究中的意义进行了探讨,并据此分析了1440年以来苟仁错地区的古气候演变。研究表明,L 值(亮度)与沉积物碳酸盐含量正相关,L 高时,气候冷干,碳酸盐含量较高;反之,气温上升,湿度增加;a 值(红—绿彩度)与沉积物中Mg含量相关,高a 值对应于沉积物中高MgO含量和高Mg/Ca比值,反映气温较高;b (黄—蓝彩度)值与三价铁的含量相关,较高的b 值代表了湖泊处于较强的氧化条件下,因此b 值可以用于反映湖水深度变化,反映有效湿度的变化,b 值高,湖水浅,氧化作用增强;苟仁错沉积物a 值和b 值曲线镜像对称进一步反映了冷干—暖湿的气候组合特征。根据沉积物的色度意义,判断苟仁错地区自1430年进入小冰期,至1890年结束。近40年来气候变化与邻近气象站的器测相吻合。Deap-sea sediment-color record from Atlantic has been widely used to reconstruct climate variation on millennial time scales. Can lake sediment color be used to reflect climate change in shorter timescale? In this paper we have discussed it based on statistical correlation between L~ *, a~ *, b~ * (CIE/L~ *a~ *b~ * color system) and some geochemical proxies. L~ * (brightness) is positive correlated with carbonate content, and higher L~ * value corresponds to higher carbonate content and cold and dry climate, and vice versa. a~ * value (red-green color) is correlated with Mg content in sediments. Higher a~ * value corresponds to higher MgO content in sediments and higher Mg/Ca ratio of sediments which reflect warmer climate. b~ * value is positively correlated with Fe~ (3+) content. Higher b~ * value represents sediments formed in oxidation condition, and b* value can indirectly reflect lake water depth change and efficient moisture change. To sediments of Gourenco Lake, the curve of a~ * value is mirrored with that of b~ * which reflects the climatic combination of cold and dry or warm and wet in this area. Based on the significance of lake sediment color in Gourenco Lake, the climate change in this area can be deduced since 1400 AD. Since 1400 AD, climate in this area has undergone several times of fluctuations. The Little Ice Age began from 1430 AD and ended at 1890 AD. Climate change in recent 40 years is coincided with instrument record of nearby meteorological stations.

关 键 词：湖泊沉积物 色度 古气候 青藏高原 苟仁错 

分 类 号：P512.32[天文地球—地质学]