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The Eocene-Oligocene boundary in the Paratethys area represents a period associated with a major extinction event followed by anoxic events. A good understanding of the factors controlling the formation of organic-rich layers is a key for prediction of source rock distributions. An excellent opportunity to study these factors is provided by the Loucka section situated in the Silesian Unit of the Czech Republic. The Menilite Formation is subdivided into the Subchert Member, Chert Member, Dynow Marlstone and Sitbořice Member and comprises non-calcareous shales, marlstones and cherts. The lithological variations reflect strongly depositional environment, which caused strong changes in geochemical parameters and source rock potential. The ratio of total organic carbon to total sulphur (TOC/TS) and methylated 2-methyl-2 (trimethyltridecyl) chroman (MTTC) ratios supported by paleontological evidence show normal marine to brackish water conditions. Pr/Ph ratios indicate strictly anoxic conditions during deposition of the upper part of the Subchert Member and the lower part of the Chert Member. Very low steranes/hopanes ratios reflect strong bacterial activity during deposition of the Chert Member. Very high HI values (>600 mg HC/g TOC) and the apparent absence of terrestrial macerals suggest that high amounts of C29 steranes and long-chain n-alkanes in this member result from the input of algal material. The Menilite Formation contains mainly type II kerogen and typically holds a “good” source rock potential. HI values > 600 mg HC/g TOC are observed in the Chert Member, while values The source potential index (SPI) of the entire succession of the Menilite Formation is about 1.25 t HC/m2, which is significantly lower than SPI determined for the Polish and Ukrainian Carpathians, but mainly due to the lower thickness.

The Most Basin represents a coal basin with a long mining history in the Czech Republic. The majority of palaeo-environmental and geochemical studies have been focused on the upper part of the coal-bearing Most Formation where the coal is generally enriched in As, Cr, Ni, Cu and Zn. This study evaluated the distribution of V, Cr, Ni, Cu, Zn, Pb, Se, As, and Mn from the lower part. Regarding to the transport of inorganic elements into environment, the evaluation of mobility potential was also conducted. The total of 51 samples were collected from the Lower Bench in the Holesice Member. The chemical analyses were performed together with optical microscopy. The X-ray spectroscopy and ICP-MS were used to detect trace element contents in the study set of samples. 4 samples were subjected to the Sequential Extraction Procedure. The prepared leachates were analysed using the ICP-MS method. In total, 13 elements were screened in samples within the study profile. The mode of occurrence is the key factor for identifying a potential source of the trace elements. All evaluated trace elements (V, Cr, Ni, Cu, Zn, Pb, Se, As and Mn) leached most in the oxidisable fraction. On the other hand, As, Mn, Ni, Zn and Cd leached in more mobile fractions, e.g. reducible and acid.

A three-dimensional reconstruction of burial and palaeogeothermal conditions is presented for Miocene sediments of the Carpathian Foredeep beneath the Outer Western Carpathians fold and trust belt in the eastern part of the Czech Republic. The sedimentary units involved include autochthonous Paleozoic sequences, Miocene deposits of the Carpathian Foredeep and of the Western Carpathian nappe system. Reservoir rocks with economic oil and gas accumulations occur in the fractured crystalline basement and in the Neogene Carpathian Foredeep. The studied Vizovice area, is characterized by rocks representing both Variscan and Carpathian orogenic cycles. The 3D thermal maturity and subsidence model presented allows the significance of both tectonic events to be evaluated. The model, calibrated by vitrinite reflectance from eight boreholes proved that eroded units related to the Variscan orogeny approach, in amount, those eroded during the Carpathian orogeny. The thickness of the eroded rocks does not exceed 300 m in either case. Vitrinite reflectance data from representative core samples of the Miocene organic matter show that Rr values increase with depth from 0.36 to 0.58%. A re-evaluation of archival data on the quantity and quality of organic matter shows that total organic carbon ranges from 0.20 to 2.92 wt%, and residual hydrocarbons (S2) from 0.04 to 8.48 mg HC/g rock. These results lead to the conclusion that Neogene Unit II that was interpreted as coastline-through to shallow-marine deposition environment within the Carpathian Foredeep in the Czech Republic is potential source rock for hydrocarbon accumulations.

The topmost Lower and Middle Jurassic formations of organic-rich clastics with minor carbonate deposits were recognized as very significant source/reservoir rocks in the North Western Desert of Egypt. Although several studies are devoted to their source rock characteristics and petroleum potential, the depositional paleoenvironment and paleoredox conditions are still poorly understood. In the current study, these sediments were assessed in terms of their organic matter richness, hydrocarbon generative potential and thermal maturity, total sulfur (TS) contents and organic petrographic characteristics. Depositional paleoenvironment was investigated using dinoflagellate cysts (dinocysts) and the composition of particulate organic matter along with organic petrographic characteristics. Redox conditions were assessed based on TS- total organic carbon (TOC) relationship and type of kerogen that was derived mainly from palynofacies analysis. TOC contents show fair to excellent generative potential of hydrocarbons mainly of kerogen type III (gas-prone). The thermal maturity, based on Tmax and Rr, indicates mature stage of oil window. Palynological analysis yielded poor to rich intervals of moderately-preserved, biostratigraphically useful dinocysts in the upper part of the Khatatba Formation. An assemblage of 81 species belonging to 54 genera of moderately diverse dinocysts, spores and pollen grains was identified. Freshwater algae, acritarchs and microforaminiferal test linings are sporadically documented within the studied interval. Based on the first downhole appearance (FDA) of the recovered marker dinocyts, the upper part of the Khatatba Formation was palynologically dated as late Bathonian-Callovian. The depositional environment was interpreted and three environments were deduced. The lower interval representing the topmost Ras Qattara and Yakout Red Shale Member was deposited in a fluvial-lacustrine environment, where oxic conditions prevailed as deduced from the color of reddish-brown sandstone and red shale. The middle interval spans Unit IIB, Kabrit and Unit III, which accumulated in a deltaic to shallow marine environment under dysoxic-suboxic settings. The upper interval covers Unit I and Unit IIA that have been deposited in a fluvio-deltaic to shallow marine with high paleoproductivity under suboxic conditions. One sample in the upper interval in Unit IIA reflected anoxic setting.

The deep boreholes in the Upper Silesian Coal Basin provide a valuable material to evaluate thermal maturity of the present Carboniferous units. 17 boreholes were used for evaluating expected paleothicknesses of the missing units and the maximum temperatures reached via 1D modelling. The models consider the geological evolution concepts accepted for the region. The reliability of the final thermal models was calibrated with vitrinite reflectance data. Vitrinite reflectance varies between 0.46 and 2.32 %Rr indicating thermally early mature to over mature organic matter for the Ostrava Fm. and Karvina Fm. The coal rank increases from the east to the west. Based on the data from RockEval pyrolysis all samples from the Ostrava and Karvina Fm. belong to type III kerogen. The RE results show that the source potential of the Carboniferous sediments was not spent in full as part of the Variscan tectogen. Burial and thermal history on the Czech side of the Upper Silesian Coal Basin was reconstructed. The set of several 1D simulations proved that the thickness of the missing Palaeozoic Molasses association is 2,500 to 3,400 m in the foreland and 1,800 to 2,000 m for the platform. The maximum burial is expected at the end of the Westphalian. The consequent sedimentation of the Carpathian Foredeep and nappe thrusting did not change the Palaeozoic thermal maturity pattern within the tested area of the USCB.

In this study a Rock-Eval pyrolysis, a petrographic composition of organic matter, vitrinite reflectance and gas chromatography were undertaken on borehole cores from the Mikulov Marls in order to define the organic matter type and determine the thermal maturity. The analyzed samples covered a depth interval of between 2,300 m and 4,500 m. The studied sediments were dark-colored, moderately laminated shale’s throughout which appear uniform upon visual examination. The geochemical analyses revealed that the source rock potential of the Mikulov Marls is from fair to good. According to the Rock-Eval pyrolysis, the organic matter in the samples was classified as kerogen type II-III. This classification is not supported by the results from the other used methods. The evaluation of the organic macerals demonstrated the dominant role of liptinite with prevailing liptodetrinite accompanied by a variable content of alginite, bituminite, and sporadic sporinite and resinite. The alginite consists mainly of lamalginite, derived from colonial planktonic or benthonic algae. Based on these results, the Mikulov Marls represent the kerogen type II. These results are also supported with a strong n-alkane odd-carbon-number predominance at n-C15, n-C17 and n-C19 range on the gas chromatography.