The discovery of mid‐Proterozoic (1.8–0.8 billion years ago, Ga) indigenous biomarkers is a challenge, since biologically informative molecules of such antiquity are commonly destroyed by metamorphism or overprinted by drilling fluids and other anthropogenic petroleum products. Previously, the oldest clearly indigenous biomarkers were reported from the 1.64 Ga Barney Creek Formation in the northern Australian McArthur Basin. In this study, we present the discovery of biomarker molecules from carbonaceous shales of the 1.73 Ga Wollogorang Formation in the southern McArthur Basin, extending the biomarker record back in time by ~90 million years. The extracted hydrocarbons illustrate typical mid‐Proterozoic signatures with a large unresolved complex mixture, high methyl alkane/n‐alkane ratios and the absence of eukaryotic steranes. Acyclic isoprenoids, saturated carotenoid derivatives, bacterial hopanes and aromatic hopanoids and steroids also were below detection limits. However, continuous homologous series of low molecular weight C₁₄–C₁₉ 2,3,4‐ and 2,3,6‐trimethyl aryl isoprenoids (AI) were identified, and C₂₀–C₂₂ AI homologues were tentatively identified. Based on elevated abundances relative to abiogenic isomers, we interpret the 2,3,6‐AI isomer series as biogenic molecules and the 2,3,4‐AI series as possibly biogenic. The biological sources for the 2,3,6‐AI series include carotenoids of cyanobacteria and/or green sulphur bacteria (Chlorobiaceae). The lower concentrated 2,3,4‐AI series may be derived from purple sulphur bacteria (Chromatiaceae). These degradation products of carotenoids are the oldest known clearly indigenous molecules of likely biogenic origin.

中文翻译：

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发现最古老的生物标记物为澳大利亚1.73 Ga Wollogorang组的光养细菌提供了证据。

发现中元古代（1.8-0.8亿年前，乔治亚州）土著生物标志物是一项挑战，因为这种古代的生物信息分子通常会被变质破坏或被钻井液和其他人为石油产品覆盖。以前，从澳大利亚北部麦克阿瑟盆地的1.64 Ga Barney Creek地层报告了最古老，最明显的生物标记。在这项研究中，我们目前从麦克阿瑟盆地南部1.73 Ga Wollogorang组碳质页岩中发现生物标志物分子，使生物标志物的记录回溯了大约9000万年。提取的碳氢化合物显示了典型的中元古代特征，其中有大量未解析的复杂混合物，高甲基烷烃/ n烷烃比和不存在真核甾烷。无环类异戊二烯，饱和类胡萝卜素衍生物，细菌类ane烷以及芳香类类an烷和类固醇也低于检出限。但是，鉴定出连续的同源序列的低分子量C ₁₄ –C ₁₉ 2,3,4‐和2,3,6-三甲基芳基类异戊二烯（AI），以及C ₂₀ –C ₂₂初步确定了AI同源物。基于相对于非生物异构体的高丰度，我们将2,3,6-AI异构体系列解释为生物分子，而将2,3,4-AI解释为可能的生物分子。2,3,6-AI系列的生物来源包括蓝细菌和/或绿硫细菌（绿藻科）的类胡萝卜素。浓度较低的2,3,4-AI系列可能来自紫色硫细菌（Chromatiaceae）。类胡萝卜素的这些降解产物是已知的最古老的可能是生物起源的本地分子。