Abstract Twenty-seven hydrocarbon source rocks from the Proteacidites asperopolus, Malvacipollis diversus and Lygistepollenites balmei biozones, Palaeogene Latrobe Group in the Gippsland Basin were analysed using gas chromatography-mass spectrometry. Based on the molecular geochemistry of the aliphatic and aromatic fractions, together with bulk geochemical data (including Rock-Eval pyrolysis and total organic carbon contents), the thermal maturity, palaeoenvironments, and organic matter source of these Palaeogene samples were systematically evaluated. The results provide a useful comparison with those from Upper Cretaceous source rocks in the Gippsland Basin (Jiang and George, 2018, 2019). Similar to the Upper Cretaceous rocks, the aliphatic hydrocarbons in the Paleogene samples are mainly comprised of n-alkanes, isoprenoids, terpanes, hopanes and steranes. The aromatic hydrocarbons are dominated by naphthalene, phenanthrene, anthracene, fluorene, dibenzofuran, dibenzothiophene and their alkyl homologues. Other aromatic hydrocarbons detected include land plant-derived compounds (e.g. retene, methylretenes, cadalene, simonellite, etc), and combustion-derived compounds (e.g. chrysene, pyrene, picene, benzo[b]fluoranthene, benzo[a]anthracene, etc). These 4- to 6-ring polycyclic aromatic hydrocarbons are more abundant in the Paleogene samples compared to the Upper Cretaceous rocks. Biomarker and aromatic hydrocarbon distributions indicate that the Proteacidites asperopolus and Malvacipollis diversus samples are immature or are in the early stage of the oil generation window, while the Lygistepollenites balmei samples correspond to the low maturity to mature stage. The samples were all deposited under sub-oxic to oxic conditions in fresh water with low salinity, possibly in a lacustrine depositional environment. The organic matter inputs are from plankton/algae and higher land plants, but are dominated by organic matter with a terrigenous origin.

中文翻译：

---

澳大利亚吉普斯兰盆地拉特罗布群古近系烃源岩中脂肪烃和芳香烃的地球化学评价

摘要 对吉普斯兰盆地古近系拉特罗布群Proteacidites asperopolus、Malvacipollis diversus和Lygistepollenites balmei生物区的27个烃源岩进行了气相色谱-质谱分析。基于脂肪族和芳香族部分的分子地球化学，结合大量地球化学数据（包括 Rock-Eval 热解和总有机碳含量），系统地评估了这些古近系样品的热成熟度、古环境和有机质来源。结果提供了与 Gippsland 盆地上白垩统烃源岩的有用比较 (Jiang and George, 2018, 2019)。与上白垩统岩石相似，古近系样品中的脂肪烃主要由正构烷烃、类异戊二烯、萜烷、藿烷和甾烷。芳烃以萘、菲、蒽、芴、二苯并呋喃、二苯并噻吩及其烷基同系物为主。检测到的其他芳香烃包括陆生植物来源的化合物（如维甲酸、甲基维甲酸、卡达林、硅锰矿等）和燃烧来源的化合物（如芘、芘、苎烯、苯并[b]荧蒽、苯并[a]蒽等） . 与上白垩统岩石相比，这些 4 至 6 环多环芳烃在古近系样品中更为丰富。生物标志物和芳烃分布表明Proteacidites asperopolus和Malvacipollis diversus样品未成熟或处于生油窗口的早期阶段，而Lygistepollenites balmei样品对应于低成熟到成熟阶段。样品均在亚氧至含氧条件下沉积在低盐度淡水中，可能是在湖泊沉积环境中。有机质输入来自浮游生物/藻类和高等陆地植物，但以陆源有机质为主。