中文摘要：

研究了藏南Cenomanian-Turonian界线缺氧沉积和Santonian-Campanian富氧沉积的稀土元素特征,重点探讨古海洋氧化还原条件变化与稀土元素地球化学之间的关系。结果表明,缺氧事件层ΣREE增加30%,Ce和Eu含量分别增加40%和114%;富氧沉积层ΣREE明显增加,其中以Eu含量增加107%最为明显,Ce增幅最小,表现为相对亏损。缺氧沉积稀土元素分布型式为Ce和Eu富集的右倾型,富氧沉积分布型式以Ce亏损和Eu富集为特征。Ce异常显示缺氧事件期间为稳定而持续的低溶解氧还原条件,而富氧事件由古海洋瞬间的氧化事件和逐渐趋于正常状态的氧化条件两个阶段组成。

英文摘要：

This paper studied the geochemistry of REEs in the anoxic and oxic sediments formed during the Cretaceous in the southern Tibet,and discussed the correlations of the geochemical behavior of REEs and the paleoceanographic redox state.Our data showed that the total concentrations of REEs in the sediments of the latest Cenomanian anoxic event increased 30%,while elements,Ce and Eu,increased 40% and 114%,respectively.High REEs content of the red mudstones was attributed to the increase of every REE,107% for Eu,38-52% for La,Nd,Sm,Tb,Yb and Lu,and 17% for Ce.Compared with other REEs,Ce is relatively depleted.The shale-normalized patterns in the anoxic event sediments are characterized by enhanced positive anomalies of both Ce and Eu elements,with LREEs are heavier than HREEs.Shale-normalized patterns in the red marlstones have a distinctively negative Ce-anomaly and a large positive Eu-anomaly.δCe values within the latest Cenomanian black shales are 1.04 in average without Ce-anomaly,showing a prevent anoxic condition.δCe decreased from 0.96 to 0.66 in the Santonian-Campanian red shales indicates a major redox state change from anoxic to oxic environment.