There was a strong relationship between paleo-oceanic conditions and organic matter accumulation during the critical period of the Early Cambrian. The Yangtze Platform in South China provides an opportunity to study this relationship, but the basin architecture and paleo-hydrographic dynamics remain poorly understood, which hinders one’s understanding of the evolution in oceanic redox state and its relationship to organic matter accumulation. To fill the knowledge gap, a newly obtained data set from the Lower Cambrian Niutitang Formation shales (Late Cambrian Stage 2-Stage 3) of the intrashelf basin is used. Results show that the molybdenum–uranium covariation, along with the abnormally low Mo contents and Mo/TOC ratios in the anoxic (ferruginous and euxinic) Niutitang shales of the intrashelf basin, indicate a hydrographic circulation that is moderately to strongly restricted. The hydrographic evolution at different stages, influencing redox conditions to a certain extent, in conjunction with variations in primary productivity, controls the enrichment of organic matter. In particular, the relatively low sea level during Interval I (Late Stage 2) resulted in weak connectivity between the intrashelf basin and open ocean; this, coupled with high primary productivity and enhanced chemical weathering, formed stable stratified water (euxinic bottom-water) conditions that were favorable for organic matter enrichment. In contrast, Interval II (Early–Middle Stage 3) and Interval III (Late Stage 3) involved less organic matter enrichment due to weakened restricted hydrographic circulation (Interval II) and oxic bottom-water conditions (Interval III). This study highlights how hydrodynamic processes affected the marine environment during the Early Cambrian and reveals that sluggish oceanic circulation combined with high primary productivity led to anomalous enrichment of organic matter. This may be a common feature of basins with restricted hydrographic circulation in deep time.

中文翻译：

---

华南早寒武世陆架盆地水文限制、氧化还原条件与有机质积累之间的联系


早寒武世关键时期古海洋条件与有机质积累之间存在密切关系。华南扬子地台为研究这种关系提供了机会，但对盆地结构和古水文动力学仍知之甚少，这阻碍了人们对海洋氧化还原状态演化及其与有机质积累关系的理解。为了填补知识空白，使用了从陆架盆地下寒武统牛蹄塘组页岩（晚寒武世第2阶段-第3阶段）新获得的数据集。结果表明，陆架盆地缺氧（含铁和缺氧）牛蹄塘页岩中钼-铀共变以及异常低的 Mo 含量和 Mo/TOC 比值表明水文环流受到中度至强烈限制。不同阶段的水文演化在一定程度上影响氧化还原条件，结合初级生产力的变化，控制着有机质的富集。特别是，第一阶段（第二阶段后期）海平面相对较低，导致陆架内盆地与外海的连通性较弱；再加上较高的初级生产力和增强的化学风化作用，形成了稳定的分层水（微生底层水）条件，有利于有机质富集。相比之下，由于受限制的水文循环（II 期）和底水氧化条件（III 期）减弱，II 期（第 3 阶段早期至中期）和 III 期（第 3 阶段后期）有机质富集较少。 这项研究强调了早寒武世期间水动力过程如何影响海洋环境，并揭示缓慢的海洋环流与高初级生产力相结合导致有机质的异常富集。这可能是深部水文环流受限的盆地的共同特征。