Czech Academy of Sciences, Institute of Geology

Coal represents a crucial energy form within the carbon cycle of the Earth's lithosphere and serves as a significant reservoir for hydrocarbon energy sources, such as natural gas. As a plastic stratum, coal rock governs the formation of structural fractures under intense stress conditions in deep strata, thereby influencing the accumulation of oil and gas. In recent years, China National Petroleum Corporation (CNPC) has extended its coalbed methane exploration from depths shallower than 1,000 meters to those exceeding 2,000 meters, achieving large-scale production in the Junggar Basin and the Ordos Basin. This endeavor has become a pivotal business segment for the company in enhancing its reserves and production capacity.The coal reservoirs in the Middle-Lower Jurassic of the Kuqa Depression in the Tarim Basin are buried at depths ranging from 0 to 8,000 meters. The cumulative thickness of coal seams is 40 to 260 meters, with a single layer thickness of 1 to 19.5 meters. The coal reservoirs buried at depths of 1,500 to 5,000 meters are relatively continuously distributed, covering an area of 5,730 km². Based on experimental analysis such as CT scanning, scanning electron microscopy, nuclear magnetic resonance, and nitrogen adsorption, outcrop and drilling samples have been conducted. It is reported that the coal reservoirs in this area have developed cleats, which are distributed in a linear and networked manner. There are 8 to 15 surface cleats per 10 cm and 13 to 24 end cleats per 10 cm. The reservoir spaces are connected, with microfractures being developed, indicating good reservoir conditions. The microfractures are mainly vertical and interlayer fractures, with good connectivity. The surface porosity ranges from 2.32% to 12.32%, and the connected porosity is 5.12%.Scanning electron microscopy reveals the development of cellular pores, primary pores, and hydrocarbon-generating pores. The matrix porosity is 10.4% to 15.5%, with the development of micro-pores (less than 10 nm) and mesopores (10 to 1,000 nm), which is conducive to the occurrence of adsorbed gas and free gas. Micropores (less than 2 nm) account for 63.4%, serving as the main adsorption space, while macropores with diameters ranging from 100 to 3,000 μm are the main occurrence space for free gas. Under the later strong thrust nappe action, the concentrated development area of coal is a regional differential structural deformation and strike-slip transformation zone, which controls the generation of fractures and the development intensity of structural fractures, and is a potential sweet-spot for reservoir development.

The chemical composition and temperature conditions of chlorite formation in metasomatic rocks of the Karagaykul ore occurrence, located in the Main Ural Fault zone in the Southern Urals, were studied. The chlorite composition was determined using a TESCAN VEGA Compact scanning electron microscope with an Xplore 15 energy-dispersive spectrometer (Oxford Instruments) at the Institute of Geology, Ufa Federal Research Center, Russian Academy of Sciences, Ufa. A geothermometer was used to estimate the temperatures of chlorite formation [Cathelineau, 1988]. It is shown that in barren propylites, chlorite is represented by ripidolite, brunsvigite, clinochlore, and pennine. The formation temperature of ripidolite is estimated at 330–364 °C, brunsvigite at 292–294 °C, clinochlore at 234–254 °C, and pennine at 208 °C. Chlorite of ore-bearing propylites corresponds to ripidolite, pycnochlorite, and diabantite, which crystallized at a temperature of 204–350 °C. Ripidolite of barren propylites is more ferruginous (X(Fe) = 0.60–0.93) compared to ripidolite of ore-bearing propylites (X(Fe) = 0.37–0.45). The main mechanism of isomorphic substitution in the chlorite structure, which controlled the changes composition chlorite from ripidolite to pennine/diabantite, is represented by the substitution of Mg2+Fe2+ in octahedral layers. In addition to the isomorphic substitution of Mg2+Fe2+ in chlorite, chermakite substitution has been established with a decrease in its share in the chlorite of ore-free (pennin) and ore-bearing (diabantite) propylites. In propylites, the change in chlorite composition was controlled by the temperature and composition of the mineral-forming fluid. In ore-free propylites, temperature played an important role in the substitution of Mg2+Fe2+ in chlorite. In ore-bearing propylites, the change in the composition of chlorite, in addition to temperature, was influenced by the activity of sulfide sulfur. Propylite chlorite crystallized in the temperature range of 204–364 °C corresponds to the temperature range of formation of propylite biotite-actinolite, epidote-chlorite and albite-chlorite-calcite facies. Their formation took place under mesothermal conditions

The characterized territory belongs to the edge of the East European Platform, adjacent to the Fore-Ural foredeep. The Yuryuzan River valley from the mouth of the Air River to the Sabakai Riverside cliff has a north-northwest direction, cutting through the southeastern part of the Ufa Plateau composed of Lower Permian rocks. The Duvan reef facies of the Sakmarian Stage is described in the Idelbaevo 1, Baganatash 1, and Baganatash 2 sections; the Yuryuzan suite of the Sakmarian Stage is known in the Kosoi Kamen, Urmantau, Manshei, Karagaitash, and Sabakai sections. The Sakmarian Stage is overlain by Lower and Upper Artinskian deposits. The outcropping in the river valley deposits form the impressive vertical riverside cliffs. The Yuryuzan River in this territory has a permanent right tributary, the Atavka River, a drying up left tributary, the Ageryav River, and a right tributary, the Koshelevka River (below Sabakai Riverside cliff). A narrow, beautiful river valley with cliffs on both sides and a plateau covered with coniferous and mixed forests are the main attractions of this area for the travellers. The authors hope that identifying and characterizing natural features will help travelers, increase interest in exploring new territories within the country, and serve as a teaching aid for local history and geography in schools.

The ichnofossil record of the early Emsian limestone-dominated succession in the Prague Synform, including the Bohemian Graptolite Event beds, was studied with a focus on ichnofabric development and its sedimentological and diagenetic implications. The studied interval yields a diverse ichnoassemblage comprising Balanoglossites, Zoophycos, Planolites, Taenidium, Phycosiphon, Trichichnus, Polykladichnus, Caulostrepsis, and possibly Trypanites, along with indeterminate biodeformational structures. The trace fossil distribution and fabric arrangement indicate a combined depositional regime characterized by episodic turbiditic influx followed by periods of relative quiescence. Some ichnological features, such as the co-occurrence of Zoophycos and Trichichnus, are shared between the Bohemian Graptolite Event interval and the uppermost part of the Dvorce-Prokop Limestone, suggesting similar environmental conditions, likely influenced by reduced oxygenation. Notably, the slightly nodular (“knobby”) structure of the studied limestones is closely linked to the presence of a Balanoglossites-dominated ichnofabric. This ichnofabric also significantly influenced subsequent diagenetic pathways, including selective dolomitization and silicification.

Taxonomic composition and biostratigraphic distribution of organic-walled microfossils and trace fossils are analyzed in Skvieryki-1s and Vychulkovskaya-201 boreholes at the southern Podlassko-Brest Depression in Belarus. The studied sections host three assemblages: two of the Lower Cambrian age corresponding to Rovno–Lontova and Dominopol’–Vergale–lower Rausve regional stages and one in the Lower–Middle Cambrian strata (upper Rausve–Kybartai regional stages). The new data expand the paleontological characteristic of the Lower Cambrian. For the first time, isolated sclerites of Wiwaxia sp. and undescribed microfossils provisionally interpreted as fragments of a mollusk radula are found in the Bug and Velikovichi formations in Belarus. These stratigraphic units also host horizontal and vertical burrows. These biostratigraphic data will help for future paleobiological, stratigraphic and paleogeographic studies.

ABSTRACT The floors of sunken houses can provide important insights into how these spaces were used and into the processes that shaped them, thereby contributing to broader interpretation at an archaeological site. When the floors are homogeneous, and the palimpsest of individual occupational horizons is difficult to distinguish, a combination of analytical methods is required. The infill of the La Tène sunken house at Němčice, Czech Republic, was analysed using a combination of sedimentology, micromorphology, geochemical analyses and frequency‐dependent magnetic susceptibility. The sediment is interpreted as an organic‐rich, homogeneous and bioturbated former floor. Its uniform character likely resulted from moisture, the availability of suitable elements for microfauna and the absence of regular maintenance. Homogenisation processes probably took place during the occupation of the house. Occasional precipitation percolating through the roof increased moisture in the sediment, while the low light conditions inside the house prevented vegetation from growing. Based on our data, we suggest that the NE quadrant served as a storage area and that the entrance to the house was located on the SW side. Interpretation of special use depends strongly on the sampling strategy applied to the floor. They must always consider the geological substrate and its topographical position in the landscape, local climatic conditions and the formation processes associated with both the use and abandonment of the floor.