The late Neoproterozoic marine succession (Marwar Supergroup) deposited in the Bikaner-Nagaur Basin in western India is an excellent provenance to study steroid biomarkers. Traditional one-dimensional gas chromatography mass spectrometry (GC–MS) and metastable reaction monitoring (MRM) transitions have been previously employed for routine biomarker analyses of crude oils and sediments. The present study with GC×GC-TOFMS (time-of-flight mass spectrometer) demonstrates an improved distribution of the sterane compounds segregated from the co-eluting n-alkanes, cycloalkanes and triterpanes in terminal Proterozoic crude oils. The steranes identified here offer novel insights into the molecular taphonomic alteration of eukaryotic lipids during the late Neoproterozoic. The presence of lanostane and 3β alkyl steranes is probably indicative of a depositional environment stressed by high salinity. To the best of our knowledge, this is the oldest known record of lanostane steroids found in the geosphere. Secosteranes with an open C-ring form as a result of diagenetic cleaving of carbon–carbon bonds. The concomitant presence of 2α-, 3β - and 4α-methyl steranes (A-ring methylated steranes) reflects specific biological input and a distinct palaeo-depositonal environment. The 3β - and 2α-methyl steranes probably form by migration of methyl substituents within the steroid structure. The recognition of a diverse range of steroid compounds by GC×GC-TOFMS advocates its excellent analytical potential in the study of natural products in geological samples. Hence, this state-of-the-art technology will be worth using for re-evaluating and investigating hydrocarbon biomarkers in order to minimize the gaps that exist in the understanding of biotic evolution over geological time scales.

沉积在印度西部比卡内尔-纳加尔盆地的晚新元古代海洋序列（马尔瓦尔超群）是研究类固醇生物标志物的极好来源。传统的一维气相色谱质谱 (GC-MS) 和亚稳态反应监测 (MRM) 转换以前已用于原油和沉积物的常规生物标志物分析。目前使用 GC×GC-TOFMS（飞行时间质谱仪）进行的研究表明，从共洗脱n 中分离的甾烷化合物的分布得到改善- 元古代原油中的烷烃、环烷烃和三萜。此处鉴定的甾烷为新元古代晚期真核生物脂质的分子埋藏变化提供了新的见解。羊毛脂烷和 3β 烷基甾烷的存在可能表明沉积环境受到高盐度的压力。据我们所知，这是在地圈中发现的最古老的羊毛甾烷类固醇记录。由于碳 - 碳键的成岩断裂，形成具有开放 C 环的节甾烷。2α-、3β-和 4α-甲基甾烷（A 环甲基化甾烷）的伴随存在反映了特定的生物输入和独特的古沉积环境。3β - 和 2α-甲基甾烷可能是通过类固醇结构内甲基取代基的迁移形成的。GC×GC-TOFMS 对多种类固醇化合物的识别表明其在地质样品中的天然产物研究中具有出色的分析潜力。因此，这种最先进的技术将值得用于重新评估和研究碳氢化合物生物标志物，以最大限度地减少在地质时间尺度上对生物演化的理解中存在的差距。