Abstract The Eocene Kosd Formation forms part of the Hungarian Palaeogene Basin. The coal measure of this formation was investigated using an 18 m drill core from borehole W–1. Petrographic and organic geochemical investigations (Rock-Eval pyrolysis, biomarker analysis) were performed in order to characterize the depositional environment, to determine the source of the organic matter within, and to assess the hydrocarbon generative potential. The presence of marine fossils, high TOC/S ratios and ash yields show that the deposition of the coal measure occurred in a marine delta with individual coal layers accumulating in low-lying, rheotrophic mires. The distribution of land plant-derived biomarkers demonstrates that the peat-forming vegetation was dominated by angiosperms, but the relative contribution of gymnosperms varied through time. In addition to land plants, algae and aquatic macrophytes contributed to the biomass. This dense vegetation established a CO2-limited environment forcing aquatic plants to utilise HCO3− during photosynthesis. The marine environment, as well as the predominance of carbonate rocks in the hinterland, caused slightly alkaline conditions, which, together with reduced oxygen availability, stimulated sulphate-reducing bacterial activity and the microbial degradation of plant remains. Consequently, Kosd Formation coal is very rich in sulphur (up to 8.8%). Moreover, the coal contains vitrinite with a strong orange-brown fluorescence colour and swells strongly during pyrolysis. These features are typical for coals with marine influences. Vitrinite reflectance, Tmax, and biomarker proxies indicate that the organic matter is thermally mature and that the Kosd coal reached the high volatile bituminous rank in the deep borehole (~2.6 km depth). Rock-Eval parameters imply that the coal is gas- and oil-prone and reached the maturity threshold critical for first gas generation and the onset of oil expulsion.

中文翻译：

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始新世 Kosd 组（潘诺尼亚盆地北部）的岩石学和有机地球化学研究：对古环境和烃源潜力的影响

摘要 始新世 Kosd 组是匈牙利古近纪盆地的一部分。使用来自钻孔 W-1 的 18 m 钻芯对该地层的煤系进行了调查。进行了岩石学和有机地球化学调查（Rock-Eval 热解、生物标志物分析）以表征沉积环境，确定其中有机物的来源，并评估碳氢化合物的生成潜力。海洋化石的存在、高 TOC/S 比率和灰分产量表明，煤系沉积发生在海相三角洲中，单个煤层堆积在低洼的流变泥沼中。陆地植物源生物标志物的分布表明，形成泥炭的植被以被子植物为主，但裸子植物的相对贡献随时间而变化。除了陆生植物外，藻类和水生大型植物对生物量也有贡献。这种茂密的植被建立了一个限制 CO2 的环境，迫使水生植物在光合作用过程中利用 HCO3−。海洋环境以及腹地碳酸盐岩占主导地位，造成微碱性条件，再加上氧气供应减少，刺激了硫酸盐还原细菌活动和植物残骸的微生物降解。因此，Kosd 地层煤的硫含量非常高（高达 8.8%）。此外，煤含有具有强烈橙棕色荧光色的镜质体，并且在热解过程中强烈膨胀。这些特征是受海洋影响的煤的典型特征。镜质体反射率，Tmax，和生物标志物代表表明有机质已经热成熟，Kosd 煤在深钻孔（约 2.6 公里深度）中达到了高挥发性沥青等级。Rock-Eval 参数意味着煤是天然气和石油倾向的，并且达到了对第一次天然气产生和开始排油至关重要的成熟度阈值。