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| 大柴旦盐湖DCD03剖面的矿物学记录及其环境指示意义 |
| A Mineralogical Record from the Sediment Section DCDO3 of Da Qaldam Salt Lake：Implications for Environmental Change |
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| DOI： |
| 中文关键词: 盐湖沉积 矿物组合 有机质烧失量 盐湖水化学演变 气候变化 |
| 英文关键词:Salt lake sediment Mineral assemblage Loss-on-ignition Evolution of lake water chemistry Climate change |
| 基金项目:国家自然科学基金项目（41171171;40871008;40571173）资助致谢：沉积物XRD分析由中国科学院青海盐湖研究所杨波协助完成,在此谨表谢意. |
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| 中文摘要: |
| 报道了大柴旦盐湖DC1303沉积剖面硼矿层及其下伏沉积地层的矿物学、有机质烧失量（LOI）等环境指标的研究结果，首次探讨硼矿层下伏灰黄色粉砂质粘土层沉积以来大柴旦湖水水化学演变及其与区域气候变化的关联。根据剖面的岩性、矿物组合和有机质烧失量（LOI）将研究剖面划分为3个沉积单元：I．灰黄色粉砂质粘土层（623～423cm）、II．灰黑色淤泥夹结核层（423—407cm）、III．柱硼铁石矿层（407—395em）。研究结果表明，在湖底硼矿层形成之前的较长时期内，大柴旦湖是碎屑沉积为主的非盐湖相沉积环境，直到单元I顶层20cm沉积物中才开始出现少量石膏。此后快速进入硫酸盐型盐湖沉积阶段（II）和湖底柱硼镁石矿层形成阶段（Ⅲ）。有机烧失量在I1、I2和I3单元中呈阶段性增加预示区域气温稳步上升，由此导致山区降水量增加和湖区蒸发量增强。湖泊环境变化是区域水文气候条件改变的结果。 |
| 英文摘要: |
| This paper reports the result of mineralogical investigation and loss-on-ignition （ LOI500 ） for the subbottom sediment section DCD03 of Da Qaidam Salt Lake. We discuss the evolution of lake water chemistry in association with regional climate change since the deposition of grayish yellow silty clay layer prior to the pinnoite deposition. Based on sediment character, mineral composition, and LOI500, the sedi- ment section is divided into three units （ I , II, Ⅲ ） ：I. grayish-yellow silty clay layer （623 - 423 cm）, II. Dark gray silt mixed with nodules （423 -407 cm）,Ⅲ. Pinnoite layer （407 -395 cm）. Results in- dicate that during the deposition of Unit I, Da Qaidam was not a salt lake, as suggested by detrital domi- nated sediments, and that the salinity of the lake began to increase near the end of the Unit I deposition as shown by the increase of calcite and occurrence of gypsum in the top 20 cm sediment interval. Unit II represents a rapid transition into a sulfate type saline lake. The pinnoite layer （Unit III） was formed in a saline lake environment. Organic matter increases in three distinct stages in the sediments of subunit I 1, 1 2and 1 3, implying a stepwise temperature increase in the ＇study area. As a result, precipitation in- creased in the mountainous area of the lake＇ s catchment and evaporation enhanced in the lake area. Changes in paleo-lake conditions, therefore, resulted from hydro-climate change. |
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