塔里木盆地西缘古海洋氧化还原条件的变化——介壳化石的稀土元素铈异常证据

本文通过对新疆塔里木盆地西缘晚白垩世至早第三纪海相地层中产出的11个贝壳化石样品的化学成分、稀土元素和20种微量元素的系统研究,着重探讨了稀土元素分布模式、铈异常程度和Th/U比值与环境的氧化还原条件之间的关系,指出塔里木古海洋在晚白垩/早第三纪时期可能局部地经历了两次氧化还原条件的波动变化。造成这种波动的原因,很可能是由于当时海平面发生升降变化,从而引起地表径流入海口发生改变所致。     

REDOX VARIATIONS OF THE ANCIENT OCEAN IN THE WESTERN MARGIN OF THE TARIM BASIN——THE EVIDENCE FROM Ce ANOMALIES OF MARINE SHELL FOSSILS

Two episodes of paleoredox fluctuation variation are indicated in some localities in thelate Cretaceous--early Tertiary ocean of western Tarim recorded by REE distribution patterns,Ce anomalies, and Th/U ratios from systematic studies on the chemical composition, withspecial reference to REE and 20 trace elements, based on 11 marine shell fossils occurringin the Upper Cretaceous--Lower Tertiary strata of the western Tarim Basin, Xinjiang. Thefactors Controlling the redox fluctuation may be probably caused by shifting places ofsurface runoff put into the sea as a result of transgression and regression.