Lipid biomarker assemblages preserved within the bitumen and kerogen phases of sedimentary rocks from the ca. 780–729 Ma Chuar and Visingsö Groups facilitate paleoenvironmental reconstructions and reveal fundamental aspects of emerging mid‐Neoproterozoic marine communities. The Chuar and Visingsö Groups were deposited offshore of two distinct paleocontinents (Laurentia and Baltica, respectively) during the Tonian Period, and the rock samples used had not undergone excessive metamorphism. The major polycyclic alkane biomarkers detected in the rock bitumens and kerogen hydropyrolysates consist of tricyclic terpanes, hopanes, methylhopanes, and steranes. Major features of the biomarker assemblages include detectable and significant contribution from eukaryotes, encompassing the first robust occurrences of kerogen‐bound regular steranes from Tonian rocks, including 21‐norcholestane, 27‐norcholestane, cholestane, ergostane, and cryostane, along with a novel unidentified C₃₀ sterane series from our least thermally mature Chuar Group samples. Appreciable values for the sterane/hopane (S/H) ratio are found for both the free and kerogen‐bound biomarker pools for both the Chuar Group rocks (S/H between 0.09 and 1.26) and the Visingsö Group samples (S/H between 0.03 and 0.37). The more organic‐rich rock samples generally yield higher S/H ratios than for organic‐lean substrates, which suggests a marine nutrient control on eukaryotic abundance relative to bacteria. A C₂₇ sterane (cholestane) predominance among total C₂₆–C₃₀ steranes is a common feature found for all samples investigated, with lower amounts of C₂₈ steranes (ergostane and crysotane) also present. No traces of known ancient C₃₀ sterane compounds; including 24‐isopropylcholestanes, 24‐n‐propylcholestanes, or 26‐methylstigmastanes, are detectable in any of these pre‐Sturtian rocks. These biomarker characteristics support the view that the Tonian Period was a key interval in the history of life on our planet since it marked the transition from a bacterially dominated marine biosphere to an ocean system which became progressively enriched with eukaryotes. The eukaryotic source organisms likely encompassed photosynthetic primary producers, marking a rise in red algae, and consumers in a revamped trophic structure predating the Sturtian glaciation.

中文翻译：

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来自晚期 Tonian 沉积岩的游离和与干酪根结合的生物标志物记录了新元古代中期海洋群落中丰富的真核生物。

大约保存在沉积岩的沥青和干酪根相中的脂质生物标志物组合。780–729 Ma Chuar 和 Visingsö 群促进了古环境重建并揭示了新兴的中新元古代海洋群落的基本方面。Chuar 和 Visingsö 群在托尼纪时期沉积在两个不同的古大陆（分别为劳伦提亚和波罗的海）的近海，使用的岩石样本没有经历过度的变质作用。在岩石沥青和干酪根氢化裂解物中检测到的主要多环烷烃生物标志物由三环萜烷、藿烷、甲基藿烷和甾烷组成。生物标志物组合的主要特征包括来自真核生物的可检测和显着贡献，包括第一次稳健出现的干酪根结合来自 Tonian 岩石的常规甾烷，包括 21-降胆甾烷、27-降胆甾烷、胆甾烷、麦角甾烷和冷冻烷，以及来自我们热成熟度最低的 Chuar Group 样品的新的未知 C _{30甾烷系列。}Chuar组岩石（S/H 介于 0.09 和 1.26 之间）和Visingsö组样品（S/H 介于0.03 和 0.37）。富含有机物的岩石样品通常比富含有机物的基质产生更高的 S/H 比，这表明海洋养分控制了真核生物相对于细菌的丰度。AC ₂₇甾烷（胆甾烷）在总 C ₂₆ –C中占优势₃₀甾烷是所有研究样品的共同特征，同时也存在少量的 C ₂₈甾烷（麦角甾烷和冰晶烷）。_{没有已知的古代 C 30}甾烷化合物的痕迹；包括 24-异丙基胆甾烷，24- n在任何这些前斯图尔特岩石中都可以检测到-丙基胆甾烷或 26-甲基柱烷。这些生物标志物特征支持这样一种观点，即托尼时期是地球生命史上的一个关键时期，因为它标志着从细菌为主的海洋生物圈向逐渐富含真核生物的海洋系统过渡。真核生物可能包括光合作用初级生产者，标志着红藻的增加，以及在 Sturtian 冰川作用之前经过改造的营养结构中的消费者。