Abstract The lower Cambrian sediments including the Qiongzhusi and Maidiping formations in the Sichuan Basin are generally considered as the main source rocks of Precambrian-Cambrian petroleum system. A comprehensive study integrated with multiple geochemical methods was conducted on 119 lower Cambrian drillcore samples collected from the upper Yangtze Platform. The results show that the fluctuation of sea level and climate during the deposition of the Qiongzhusi and Maidiping formations act as the critical factors controlling the watermass conditions and thus OM accumulation. During the deposition of upper Maidiping Formation (Є1m), the paleoclimate was arid and sea level was relatively low in the study area. The depositional environment indexes (UEF-MoEF, gammacerane index, β-carotane and VEF) suggested that the upper Є1m was deposited in a strong restricted marine setting with high water salinity and anoxic water conditions in Ziyang-Weiyuan area. However, during the early Qiongzhusi Formation period, the paleoclimate became humid and sea level rose in the study area. High paleoproductiviy caused by high concentrations of nutrients brought by seawater and freshwater plays an important role in OM accumulation in the basal part of the Qiongzhusi Formation (Є1q). Furthermore, the model of paleoproductivity promotion caused by the coordinated control of climate and extensive transgression in the lower part of Є1q may also be applicable to interpret the origin of high organic carbon abundance in the strata deposited in the same period with the Є1q (such as Shiyantou, Shuijingtuo and Niutitang formations) in other parts of the upper Yangtze Platform.

中文翻译：

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上扬子地台下寒武统黑色页岩沉积水团条件及有机质富集的气候-海洋控制

摘要 四川盆地筇竹寺组和麦地坪组等下寒武统沉积物被普遍认为是前寒武系—寒武系油气系统的主要烃源岩。结合多种地球化学方法对上扬子地台采集的119个下寒武统钻芯样品进行了综合研究。结果表明，筇竹寺组和麦地坪组沉积过程中海平面和气候的波动是控制水团条件和有机质积累的关键因素。研究区麦地坪组上段（Є1m）沉积期古气候干旱，海平面相对较低。沉积环境指数（UEF-MoEF、伽玛蜡烷指数、β-胡萝卜素和VEF)表明，上Є1m沉积在资阳-威远地区水盐度高、水体缺氧条件强的受限海相环境中。但在筇竹寺组早期，研究区古气候变湿润，海平面上升。由海水和淡水带来的高浓度养分引起的高古生产力在筇竹寺组底部(Є1q)的有机质积累中起重要作用。此外, Є1q 下部气候协调控制和大面积海侵导致的古生产力提升模型也可用于解释与Є1q 同期沉积的地层有机碳丰度高的成因(如十堰，