安徽胡乐寒武——奥陶系界线地层地球化学特征

作者在胡乐寒琥－奥陶系界线剖面上作了多种地球化学测试。依据测试结果，分析了地球化学特征，碳、氧同位素、微量元素和稀土元素组成 于西阳山组与谭家桥组之间，它可能与海平面变化有关。在寒武－奥陶系岩界线上仅见有小的碳同位素负偏移。

GEOCHEMICAL VARIATION ACROSS CAMBRIANORDOVICIAN BOUNDARY IN THE HULE SECTION,ANHUI PROVINCE

The Cambian-Ordovician boundary section in Hule is 0ne of the well-established section of this stratigraphic sequence. Fossils from bed 5 to bed 12 are dominated by the graptolites. Two graptolite zones were recognized. They are the Staurograptus zone in the lower and the Anisograptus-Clonograptus zone in the upper. No fossil graptolites have been found from bed l to bed 4 except of trilobite Charchaqia? sp. Accordingly, the Cambrian-0rdovician boundary is placed on the base of Bed 5. However, only minor negative excursion of δ13C displays across the Cambrian-Ordovician boundary though the trilobites dominated shelly fauna was replaced by the graptolites dominated pelagic fauna around this leve1. Dramatic changes in value ofδ13C, δ18O and REE appear across the boundary between two lithostratigraphic units, i.e.the TangJiaqiao and the Xiyangshan Formations. These conspicuous geochemical changes are likely coincident with shifting from anoxic to oxide environments following rapid falling of sea-leve1.