渤海东部晚第四纪沉积环境变化的稀土元素地球化学记录

Rare earth element records of palaeoenvironmental changes during the Late Quaternary from core sediments of the eastern Bohai Sea

对渤海东部DLC70-1孔157个沉积物样品进行了稀土元素（REE）测定，结合有孔虫丰度和粒度参数研究，探讨了该孔稀土元素地球化学特征与晚第四纪环境变化关系。DLC70-1孔沉积物物源分析表明，该孔沉积物物质来源比较稳定，其沉积物主要来源于黄河。渤海东部DLC70—1孔REE的分布特征与晚第四纪沉积环境变化密切相关，约100kaBP以前，研究区发育浅海环境，∑REE含量较高，且HREE相对富集。100～75kaBP期间，2REE含量受沉积物粒度的影响，明显低于前一阶段，LREE相对富集，稀土元素分布表现为河口半咸水环境特征。75～60kaBP期间，研究区发育以细颗粒沉积物为主，∑REE含量达到高值。60-35kaBP期间为晚更新世玉木冰期中间冰阶（暖期）沉积，研究区发育滨海沉积环境，其∑REE含量总体较低，并显示LREE相对富集；随着水体深度和盐度条件发生多次波动，稀土元素分布特征也表现出小幅度变化。35～30kaBP期间，研究区发育滨岸和滨海沉积环境，其∑REE含量总体较高。30～10kaBP期间，研究区表现为河流环境，受矿物组成和沉积物粒度的影响，∑REE含量总体较低，显示向上HREE相对富集。10kaBP以来为全新世海侵期，研究区持续发育滨海一浅海沉积环境，其∑REE含量总体较高，显示LREE富集。

157 sediment samples were collected from core DLC70-1 in the eastern Bohai Sea. These samples were analyzed for rare earth element （REE） composition, foraminifera abundance and grain size parameters. The rare earth element distribution and sedimentary environmental changes during the Late Quaternary were studied. Discrimination plots based on REE fractionation parameters showed that the cored sediments originated mostly from the Yellow River. The REE distribution in core DLCT0-1 was closely related to sedimentary environmental changes during the Late Quaternary in the eastern Bohai Sea.Before approximately 100 ka BP, a shallow sea environment developed in the study area. The sediments had a higher ∑REE concentration and showed HREE enrichment. The sediments dated from 100 to 75 ka BP were possibly deposited in a brackish-water environment, with a low ∑REE and a clear enrichment of LREE relative to HREE, which was under the effect of grain size. The sediments dated from 75 to 60 ka BP were possibly deposited in fine-grained sediments resulting in highest ∑REE concentrations. During late last interglacial cycle （warm period） from around 60 to 35 ka BP, a littoral environmentdeveloped in the study area. The sediments had a lower ∑REE concentration and showed LREE enrichment. The beach and littoral environments developed in the study area from around 35 to 30 ka BP, and the sediments had a higher ∑REE concentration. During the first phase of the postglacial sea-level rise （from around 30 to 10 ka BP） , a river environment developed in the study area, which was under the effect of heavy mineral concentration and grain size, with a lower ∑REE and a clear enrichment HREE upper. Since 10 ka BP, a littoral shallow sea environment developed in the study area. Correspondingly, the sediments generally exhibited an enrichment of∑REE, particularly LREE.