上奥陶统-下志留统烃源岩是中国南方海相4套主力区域烃源岩之一,有关它形成与发育环境的研究是南方海相油气成藏理论的基础性问题.本文选择中上扬子南缘2条代表性剖面,对上奥陶统-下志留统沉积岩进行了详细的地球化学分析,提取其中对沉积古环境有指示意义的地化指标,对该段地层的古环境进行了恢复.研究表明,优质烃源岩段主要集中在上奥陶统五峰组和下志留统龙马溪组底部,V/(V+Ni)、Ni/Co、Ce_(anom)、δEu和δ~(13)C_(org)等地球化学指标与有机碳含量均有较好的相关性,这些指标的异常均表明优质烃源岩发育于缺氧环境.而龙马溪组上部地层的有机碳含量较低,各种地球化学指标也显示,此时缺氧环境遭到了破坏,这与当时的沉积环境多为高能环境、不利于烃源岩发育是一致的.%The hydrocarbon source rock in Upper Ordovician-Lower Silurian strata is one of the four kinds of regional marine source rocks in southern China, and the researches on the palaeo-environment for its formation and development constitute one of the basic problems concerning the marine hydrocarbon accumulation theories of southern China. Two typical sections were selected in this study, and a detailed geochemical analysis of Upper Ordovician-Lower Silurian sedimentary rocks was conducted along these sections. Environment indicators were chosen to restore the palaeo-environment. The results show that the high-quality source rocks are concentrated in Upper Ordovician Wufeng Formation and at the bottom of Lower Silurian Longmaxi Formation. Such indicators as V/(V + Ni), Ni/Co, Ce_(anom), δEu and δ~(13)C_(org) have good relations with TOC in these formations, suggesting that good quality hydrocarbon source rocks are developed in an anoxic environment. Geochemical indicators in the upper part of Longmaxi Formation show that the anoxic environment had been destroyed, which was accordant with the high-energy sedimentary environment at that time and was disadvantageous to the formation of hydrocarbon source rocks.
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