This study presents the results of an organic geochemical characterisation of a liquid hydrocarbon sample from the Ormož-1g well in the Mura-Zala Basin, north-eastern Slovenia. The main objective was to assess the origin, depositional environment, and thermal maturity using biomarker analysis. The bulk composition of the sample was initially determined by gas chromatography. The hydrocarbon sample was then fractionated into saturates and aromatics. These fractions were analysed by gas chromatography–mass spectrometry (GC–MS) to identify and quantify specific biomarker compounds. Based on an API gravity of 42.53° and biomarker distribution of the saturated fraction, the sample is classified as light crude oil. The dominance of high molecular weight n-alkanes and a Pr/Ph ratio of 1.83 suggests suboxic marine depositional conditions with significant terrestrial organic matter input. The sterane distribution pattern and the isoprenoid/n-alkane ratio indicate a mixed origin of organic matter. The uniform distribution of n-alkanes, a CPI value close to 1, a high degree of sterane isomerisation and the relative abundance of 3- and 2-methylphenantherene collectively indicate high thermal maturity. These establish a geochemical framework for further hydrocarbon exploration in the Mura-Zala Basin and enhance the understanding of its petroleum potential.
Foraminiferal assemblages and proportions of foraminiferal morphogroups were determined from Upper Triassic deposits of the Eiberg Basin and the Hallstatt Zone of the Northern Calcareous Alps in Austria (Eastern Alps). Foraminifera were hand-picked from the residue of marl samples taken from the upper Norian Pötschenkalk Formation, the middle–upper Rhaetian Zlambach Formation, and the uppermost Rhaetian Tiefengraben Member of the Kendlbach Formation. In total, 72 species from 31 genera were determined. Foraminiferal assemblages from the Pötschenkalk Formation at the Thälerergraben section are relatively diverse. Dentalina, Ammodiscus, Nodosaria, and Glomospirella dominate. Foraminiferal assemblages from the Zlambach Formation at the Rossmoos-/Stambachgraben section are also abundant and diverse. The most common foraminifera are Reophax, Dentalina, and Annulina. The uppermost Kössen Formation at the Schlossgraben section is dominated by hyaline taxa. The most common genera are Ichthyolaria, Lenticulina, and Nodosaria. At the Fonsjoch section, the uppermost Kössen Formation contains Lenticulina, Astacolus, and Trochammina. An increase in opportunists suggests variations in oxygen levels during the deposition of the uppermost Kössen Formation. The Kendlbach Formation at the Schlossgraben section is dominated by Lagenida over agglutinated taxa. Astacolus, Lenticulina, and Trochammina are the most common genera. At the Fonsjoch section, the Kendlbach Formation contains mostly Astacolus, followed by Trochammina, Ammobaculites, Reophax, and Lenticulina. Increases in opportunists point to increased stressful conditions. An increase in nodosariid foraminifera higher up the section indicates a return to better oxygenated conditions.
The Tithonian–Berriasian Chia Gara Formation in Central Iraq represents a major breakthrough in shale oil exploration. This study investigates two continuous core sections (140 m and 137 m) from the East Baghdad (EB1) and Balad (Ba1) oilfields, located within the intrashelf basin along the passive margin of the Arabian Plate. Comprehensive geochemical analyses, including major and trace elements, Mo isotopes, and total organic carbon (TOC), were conducted to evaluate the mechanisms controlling organic matter enrichment. The EB1 and Ba1 cores are subdivided into five and four organic sedimentary facies (OSF), respectively. In EB1, TOC values in the lower OSF 1 and OSF2 range from 3.55 to 8.0 wt.% and 2.31 to 4.42 wt.% and are higher than those of the upper OSF 3, OSF 4, and OSF 5 that range from 0.5 to 3.77 wt.%. In Ba1, OSF 3 and OSF 5, which range from 0.39 to 2.7 wt.%. Redox indicators such as U/Th, Ni/Co, EF(U), and EF(Mo) show a progressive shift towards more oxic bottom-water conditions. The δ98/95Mo data (–0.3 to 2.5‰) confirm the presence of euxinic conditions, particularly within OSF2 in both EB1 and Ba1, thereby resolving previous uncertainties regarding bottom-water redox conditions. Primary productivity indices (Cu/Al and Ni/Al ratios) suggest relatively low productivity in deep-water slope and basinal facies. Furthermore, the upwelling indicators (EF(Co) × EF(Mn)), varying from 0 to 0.48 for EB1 and 0.05 to 0.18 for Ba1, suggest that preservation conditions played a more significant role than productivity conditions within the deep-water slope and basin. Differential subsidence, with local uplifts and erosion within the Mesopotamian Foredeep Basin likely contributed to spatial variability in organic enrichment. Overall, this study highlights the importance of the redox environment in the development of high-quality hydrocarbon source rocks in unrestricted environments that present upwelling.
The Slovenian Basin was the largest Mesozoic inter-platform deeper-marine palaeogeographic unit of the transitional zone between the present-day Southern Alps and the Dinarides. In this study, we present the sedimentology and biostratigraphy of the Toarcian to Tithonian succession of the last unstudied large outcrop belt of the Slovenian Basin Jurassic rocks, which occurs in the Kneža Valley in the foothills of the Julian Alps in NW Slovenia. The studied succession is typical of the southern part of the Slovenian Basin preserved in the Podmelec Nappe, the lowest thrust unit of the eastern segment of the Southern Alps. In two detailed sections, we logged the hemipelagic limestones of the uppermost Krikov Formation, the clay-rich Toarcian Perbla Formation, siliceous pelagites, and resedimented limestones of the Aalenian to Lower Tithonian Tolmin Formation, and calpionellid-bearing Upper Tithonian to Lower Berriasian Biancone Limestone Formation. The thickness of the Perbla Formation follows the eastward thickening trend typical of the successions along the southern part of the basin. The Tolmin Formation shows a high abundance of resedimented limestones, which is also in accordance with the previously established northward waning of resediments within the entire basin. A distinctive feature of the Kneža Valley succession is the unusually small thickness of the radiolarian cherts of the Tolmin Formation (its Upper Member). This indicates a stratigraphic gap, which is related to the Bajocian-Bathonian collapses of the basin’s southern slopes and the margin of the Adriatic Carbonate Platform.
Environmental geophysical investigations require controlled laboratory experiments to better understand the relationships between the parameters measured in the field and complex physicochemical processes occurring in the subsurface. In this work, we introduce the Geoelectrical Laboratory (GEL) of the Geological Survey of Slovenia. A typical application of the spectral induced polarization (SIP) method, focussing on the detection of electron-conducting minerals disseminated in geologic material is presented. This is demonstrated by the close relationship between the polarization peak values, and chargeability values associated with the second peak (m2) of polarization spectra estimated from a double Cole-Cole fit, and the metal content, either by the mass % concentration of the ore mineral or the chemical composition (Pb, Zn and Fe) estimated by XRF measurements. We illustrate this for synthetic mixtures of quartz sand and pure Pb-Zn ore particles from the Mežica mine (Slovenia), the Mežica Pb-Zn mine waste material (K-material) and sediments collected from streams near the waste deposits (S-material). These results evidence promising capabilities of the SIP method for in-situ detection of metallic particles, both within the mine waste deposits and sediments in the surrounding areas. However, further SIP investigations are needed in a larger number of material samples along with geochemical, mineralogical, and granulometric data to refine the links of polarization and chargeability to both the mass content of ore and the specific geochemical composition of the materials under investigation, as well as to determine the influence of the natural geological materials that constitute both the host rock of Pb-Zn ore and the surrounding sediments (e.g., carbonates).
