Abstract The Piramboia Formation tar sands constitute one remarkable occurrence of heavy oil in the eastern border of the Parana Basin, Sao Paulo State, Brazil, being characterized as highly degraded oils related to the Irati-Piramboia oil system. In this context, the aim of the present work was to investigate biomarkers that are more resistant to degradation and use them to establish a more reliable geochemical correlation between the tar sand oils of the Piramboia Formation (collected from the Fazenda Betumita and Guarei I outcrops) and the organic extracts of black shales of the Irati Formation (facies Irati A and B, collected in the Amaral Machado Quarry, Sao Paulo State). For this purpose, analysis of stable carbon isotopes and diagnostic ratios of saturated and aromatic biomarkers were investigated, and the most reliable diagnostic ratios were selected based on the principal component statistical analysis. The results pointed to different degradation extent between the tar sand outcrops, being higher for the Guarei I samples. In this scenario, it was verified that most of the diagnostic ratios commonly used in oil-source rock correlation studies were susceptible to degradation processes. It was also observed that samples from Piramboia and Irati formations are at the beginning of the oil generation window, with the C29 ββ/(αα + ββ) ratio as the most suitable to assess thermal maturity of extremely degraded oils. The multivariate statistical analysis of the results, based on ten more resistant diagnostic ratios, allowed to select six main variables responsible for the similarity between the samples from the Irati and Piramboia formations: δ13C (‰), TPP ratio (C30 tetracyclic polyprenoids over diasteranes), %C28 and %C29 monoaromatic steranes, (C20 + C21)/(C23 + C24) tricyclic terpanes, and C23 tricyclic terpane/(C23 tricyclic terpane + C29 hopane). These geochemical parameters showed greater reliability in the correlation between the Piramboia Formation tar sand oils and the Irati samples of the facies A, deposited in a restricted marine environment under anoxic-euxinic conditions.

中文翻译：

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Pirambóia 组焦油砂（三叠纪）中的抗降解生物标志物及其与巴拉那盆地（巴西）Irati 组烃源岩（二叠纪）有机相的相关性

摘要 Piramboia 组焦油砂是巴西圣保罗州Parana 盆地东部边界的一个显着稠油产地，其特征是与Irati-Piramboia 石油系统相关的高度降解油。在此背景下，本工作的目的是研究更耐降解的生物标志物，并使用它们在 Piramboia 地层的焦油砂油（从 Fazenda Betumita 和 Guarei I 露头收集）之间建立更可靠的地球化学相关性以及 Irati 组黑色页岩的有机提取物（Irati A 和 B 相，收集于圣保罗州的 Amaral Machado 采石场）。为此，研究了稳定碳同位素的分析以及饱和和芳香生物标志物的诊断比率，并根据主成分统计分析选择最可靠的诊断比率。结果表明，焦油砂露头之间的降解程度不同，Guarei I 样品的降解程度更高。在这种情况下，证实了油源岩相关性研究中常用的大多数诊断比率容易受到退化过程的影响。还观察到来自 Piramboia 和 Irati 地层的样品处于生油窗口的开始，C29 ββ/(αα + ββ) 比率最适合评估极度降解油的热成熟度。结果的多变量统计分析基于另外十个抗性诊断比率，允许选择六个主要变量，这些变量负责 Irati 和 Piramboia 地层样本之间的相似性：δ13​​C (‰)、TPP 比（C30 四环聚异戊二烯相对于非甾烷）、%C28 和 %C29 单芳香甾烷、(C20 + C21)/(C23 + C24) 三环萜烷和 C23 三环萜烷/(C23 三环 C29 萜烷) . 这些地球化学参数表明，在 Piramboia 组焦油砂油与 A 相 Irati 样品之间的相关性方面具有更高的可靠性，A 相沉积在缺氧-富氧条件下的受限海洋环境中。