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The Early Cambrian Late Stage 2 to Stage 3 (ca. 526–514 Ma) was characterized by the peak of the Cambrian Explosion and a large-scale global transgression that resulted in the deposition of organic-rich black shales, which have important implications for Earth-system science and petroleum/economic geology. However, there are many uncertainties regarding the spatiotemporal evolution of structural model, and driving mechanisms of the paleo-oceanic environment during this period, requiring more examples and research constraints. To fill the knowledge gap, high-resolution elemental, carbon isotope, and biogeochemical data were obtained from two continuous drill cores, along with redox-sensitive proxy data from additional 21 cores/sections of different sedimentary facies in the Yangtze Platform, South China, provide a comprehensive and detailed spatiotemporal window into this issue. It demonstrates that the dynamic evolution process of redox conditions varied between shallow- and deep-water regions, and temporal variations in chemical weathering intensity and spatiotemporal differences in upwelling currents controlled the redox state of the ocean, which was closely related to the relative contents of organic carbon (TOC), SO 4 2−, and Fe2+. The mechanisms that controlled the scale of sulfidic wedges differed among different regions and stages. During intervals I (Late Stage 2) and II (Early–Middle Stage 3), shallow and deep waters were controlled mainly by TOC and SO 4 2− contents, respectively. Deep waters during interval III (Late Stage 3) were controlled mainly by TOC contents. The spatiotemporal heterogeneity of the Early Cambrian paleo-ocean redox state partly controlled the spatiotemporal distribution of the fossil record. Primary productivity was the main controlling factor on the spatiotemporal variations in hydrocarbon source rock quality, followed by the organic matter preservation conditions. This study highlights the Earth-system science research on the deep-time ocean environment and its resource effects. [ABSTRACT FROM AUTHOR]

The Permian Junggar Basin was the site of deposition of a large set of organic-rich sediments, among which the Lucaogou Formation is considered an excellent petroleum source bed. High-frequency variation in lithology is a typical feature of the Lucaogou Formation, reflecting the fluctuation of the paleoclimate and depositional environment. The relationship between climate fluctuation and organic matter enrichment still needs to be elucidated for the Lucaogou Formation. High-resolution sampling was applied to an 86.2 cm long core from the Lucaogou Formation from the Jimsar Sag in the Junggar Basin to examine the effects of climate fluctuation on organic carbon burial. Petrographic, mineralogical, and elemental analyses of the core indicated that the paleoclimate for the core went through a relatively wet-dry-wet sequence, with changes occurring on timescales of thousands of years. The influence of climate fluctuation on organic matter accumulation is multilevel and multifactorial, involving chemical weathering, sediment supply, lake level, paleosalinity, redox, and primary productivity. High-resolution geochemistry portrays the evolution of these factors and how they collectively determine the burial of sedimentary organic carbon. The Lucaogou epoch was generally characterized by dry/cold climatic conditions, low weathering intensity, and limited detrital input. Moreover, low temperatures and scanty nutrient input resulted in low to moderate productivity. The enrichment of organic matter in the Lucaogou Formation was primarily controlled by preservation. • Paleoclimate mediated organic matter enrichment through a complex multilevel and multifactorial process. • Chemical weathering, sediment supply, salinity, redox, and primary productivity changed along with fluctuating climates. • Organic matter accumulation was mainly controlled by preservation rather than primary productivity and mineral dilution. [ABSTRACT FROM AUTHOR]