Upper Triassic (Carnian - Julian) bedded dark limestone in the Lesno Brdo area, more precisely in the Drenov Grič quarry (Central Slovenia), was investigated in this study to describe its carbonate facies, its geochemical characteristics of the inorganic and organic matter, and to estimate its hydrocarbons generative potential. The site was chosen as a well referenced location of previous lithological and paleontological studies with the aim to fill a gap in the up-to-date knowledge on organic petrology of the investigated rocks termed as the Julian “Carbonate Member” within the Lesno Brdo stratigraphic sequence. The study represents the first multi-analytical organic petrological investigation of Mesozoic carbonate rocks in Slovenia. In the Drenov Grič (DRG) section, 7 microfacies were defined. A total of 38 DRG samples of micritic limestones, marlstones, and a coaly sample were collected from the section. The average total organic carbon (TOC) content of the samples is 0.70 wt% with one outstanding sample DRG-28 with a TOC content of 15.56 wt.%. According to the TOC content, DRG samples are considered as a fair to good source rock for hydrocarbons generation. In addition, the samples with TOC >0.5 wt.% were characterised by the Rock-Eval S₁, S₂ and S₃ peaks, hydrogen and oxygen indices (HI, OI), T_max and production index (PI) values. According to these data, typical “black” Julian carbonate beds from the Drenov Grič locality are poor source rocks. Based on pyrolysis data (HI versus OI), the type of the organic matter could not be determined, so a micropetrographic examination was performed. . The predominant and the only clearly visible maceral in the DRG samples is vitrinite within the amorphous organic matter. Given the low S₂ peaks, thermal maturity was determined by vitrinite reflectance. Vitrinite reflectance results (between 2.71 ± 0.19 %R_o and 3.89 ± 0.17 %R_o) indicate that the organic matter in the DRG samples is in a thermally mature to overmature stage, which is also consistent with the Thermal Alteration Index (TAI) (4^- - 4). All 38 samples were also analysed on main and trace elements, focusing on the redox sensitive trace elements (Ni, Mo, Th, U, V and Zn) to supplementary interpret depositional conditions. Overall, the “black” carbonate rocks of the Drenov Grič section show a negligible potential for the generation of hydrocarbons. Their original dispersed organic matter was thermally strongly transformed. Therefore, the investigated carbonate rocks almost completely exhausted their ability to generate a considerable quantity of hydrocarbons. They can therefore be classified as “spent source rocks”, which could conditionally generate some dry gas.

在这项研究中，对莱斯诺布多地区（更确切地说是斯洛文尼亚中部的德雷诺夫·格里奇采石场）的上三叠纪（卡纳-朱利安）层深色石灰岩进行了描述，以描述其碳酸盐相，无机和有机物的地球化学特征，以及估算其碳氢化合物的产生潜力。该地点被选为先前岩性和古生物学研究的参考位置，目的是填补被调查岩石的有机岩石学最新知识中的空白，该岩石被称为Lesno Brdo地层中的朱利安“碳酸盐岩成员”。顺序。该研究代表了斯洛文尼亚中生代碳酸盐岩的首次多有机有机岩石学研究。在DrenovGrič（DRG）部分中，定义了7个微相。总共38个微影石灰岩的DRG样品，从该断面中收集了泥灰岩和一个含煤的样品。样品的平均总有机碳（TOC）含量为0.70 wt％，其中一种出色的样品DRG-28的TOC含量为15.56 wt。％。根据TOC含量，DRG样品被认为是生成烃的优质烃源岩的公平条件。此外，TOC> 0.5 wt。％的样品通过Rock-Eval S进行表征_在图1中，S ₂和S ₃峰，氢和氧指数（HI，OI），T _max和生产指数（PI）值。根据这些数据，来自德雷诺夫格里奇地区的典型“黑色”朱利安碳酸盐岩层是不良的烃源岩。根据热解数据（HI与OI），无法确定有机物的类型，因此进行了显微金相检验。。DRG样品中主要且唯一清晰可见的显微图像是无定形有机物中的镜质体。鉴于低的S ₂峰，热成熟度由镜质体反射率确定。黑tri石反射率结果（介于2.71±0.19％R _o和3.89±0.17％R _o之间）表明DRG样品中的有机物质是在热成熟为成熟阶段，这是也与热蚀变指数（TAI）（4一致^- - 4）。还对所有38个样品的主要和痕量元素进行了分析，重点是对氧化还原敏感的痕量元素（Ni，Mo，Th，U，V和Zn），以补充解释沉积条件。总体而言，DrenovGrič断面的“黑色”碳酸盐岩显示出的碳氢化合物潜力可忽略不计。他们最初的分散有机物被热强烈地转化。因此，所研究的碳酸盐岩几乎完全耗尽了它们产生大量碳氢化合物的能力。因此，它们可以归类为“废源岩”，可能有条件地产生一些干气。