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The reciprocating shear mechanical properties and strength deterioration mechanisms of rockfill materials are of great research significance for high-fill slope stability analysis. To study the shear strength characteristics of argillaceous siltstone rockfill materials with different fabric characteristics under reciprocating shear loading, we analyzed the shear strength, hysteresis loop area, damping ratio, shear strength parameter, and shear stiffness of coarse-grained soils with different coarse grain contents using a coarse-grained soil direct shear testing machine capable of reciprocating shear and revealed their strength deterioration mechanism. The test results show that the shear strength of argillaceous siltstone rockfill materials is significantly affected by the coarse grain content and the number of reciprocating shears. Specifically, the shear strength increases with the coarse grain content and decreases with the number of reciprocating shears. The hysteresis loop area is positively correlated with the coarse grain content and negatively correlated with the number of reciprocating shears. The damping ratio is not related to the coarse grain content but tends to decrease with the number of reciprocating shears. Soil cohesion and the internal friction angle increase with the coarse grain content and decrease with the number of reciprocating shears. The soil failure shear stiffness is linearly correlated with the coarse grain content, and the normalized shear stiffness is logarithmically related to the number of reciprocating shears. According to these relationships, an empirical formula for the shear stiffness of argillaceous siltstone rockfill materials under different coarse grain contents and different numbers of reciprocating shears can be established to provide a basis for analyzing rockfill stability. [ABSTRACT FROM AUTHOR]

Extra care should be taken when new tunnels pass through an existing tunnel. If it is not handled properly, this will affect the operation safety of the existing line, and bring security risks to the train's operation. In order to study the impact of an under-crossing parallel double-line shield tunnel on the existing shield tunnel structure, the influence of tunnel construction on the deformation of overlying strata was analyzed, and the formula for estimating the formation settlement at depth Z below the surface, caused by the excavation of a double-tunnel parallel tunnel, was deduced. Then, a series of three-dimensional finite element numerical simulations were carried out. We analyzed and systematically studied the adverse effects of the tunnel structure of Guangzhou subway Line 5, caused by the tunneling of subway Line 18, evaluated its structure and operational safety, and provided suggestions for site construction. This research demonstrates the following conclusions. (1) The tunnel structures of subway Line 5 and Line 18 are mainly in the strongly weathered argillaceous siltstone stratum, and lightly weathered argillaceous siltstone stratum, respectively, and the stratum where the Line 18 tunnel is located is relatively safe. (2) According to three-dimensional finite element numerical simulation analysis, during the shield-tunneling process of subway Line 18, the maximum X horizontal displacement, the maximum Y horizontal displacement, and the maximum Z vertical displacement of the tunnel structure in subway Line 5 are 1.09, 3.50, and 4.55 mm, respectively. It is considered that the impact of the shield-tunnel penetration of subway Line 18 on the tunnel structure of subway Line 5 is relatively controllable, and does not affect the structure and operational safety. (3) It is suggested that settlement monitoring should be strengthened within the range of 12 m (about 1.5 tunnel diameter D). before and after the excavation axis of the underpass tunnel, and it is necessary to carry out local reinforcement treatment, to prevent adverse effects on the operation of the existing tunnel. [ABSTRACT FROM AUTHOR]

Kinkasi is one of the oil fields of the DR Congo Coastal Basin. It is essentially formed of two main geological units (A and B) in the Turonian, each composed of a succession of different horizons (Zones) according to the type of siltstone. These two main units contain 6 Zones. Unit A consists of Z6 and Z5 of Coniacian age, while the rest of the reservoir (Z4, Z3, Z2 and Z1) is of Turonian age which is characteristic of Unit B. Indeed, the present study is devoted to the petrophysical characterization of the two zones Z4 and Z3 of the unit B in order to locate the interesting zones to develop this oil field. For this fire, we used the data of 11 wells having the geographical coordinates, the porosity, the permeability as well as the water saturation. The processing and interpretation of these data using the Kriging method allowed us to deduce from the scale of appreciation the areas that contain high values of porosity, permeability and water saturation. Porosity in zones 4 and 3 varies from good to very good, saturation 3 to 59% for zone 4 and 32 to 53% for zone 3 as well as permeability from poor to low for both zones. The combined interpretation of these three properties allowed us to find an interesting zone located towards the east of zones 4 and 3 with high porosity and permeability values and low water saturation values. [ABSTRACT FROM AUTHOR]

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In this study, we used high-resolution optical satellite images on the Google Earth platform to map large-scale landslides in Xianyang City, Shaanxi Province, China. After mapping, a comprehensive and detailed large-scale landslide inventory that contains 2924 large-scale landslides was obtained. We analyzed the spatial distribution of landslides with seven influencing factors, including elevation, slope angle, aspect, curvature, lithology, distance to a river, and distance to the fault. Landslide Number, Landslide Area, Landslide Number Density (LND), and Landslide Area Percentage (LAP) were selected as indexes for the spatial distribution analysis. The results show that the number and area of landslides in the elevation range of 1000–1200 ​m is the highest. The highest number of landslides was observed in the slope angle of 25°–30°. North-facing slopes are prone to sliding. The area and number of landslides are the largest when the slope curvature ranges from −1.28 to 0. The LND and LAP reach their maxima when the slope curvature is less than −2.56. Areas covered by the Tertiary stratum with weakened fine-grained sandstone and siltstone show the highest LND and LAP values. Regarding distance to a river, the LAP peaks in the range of 300–600 ​m, whereas the LND peaks in an area larger than 2100 ​m. The values of LND and LNP rise as the distance from the faults increases, except for the locations 30 ​km away from active faults. This phenomenon is because active faults in this area pass through the plain areas, while landslides mostly occur in mountainous areas. The cataloging of landslide development in Xianyang City provides a significant scientific foundation for future research on landslides. In addition, the spatial distribution results are useful for landslide hazard prevention decisions and provide valuable references in this area. [ABSTRACT FROM AUTHOR]

The Nahr Umr Formation is considered one of the main reservoirs produced in southern Iraq. It is one of the important siliciclastic deposits of the Cretaceous sequence of Iraq oilfields. Zubair oil fields ZB-190 and ZB-047 were chosen to study areas. This study depends on the available core and cutting samples to determine the facies analysis, depositional environments, petrographic characteristics and diagenesis processes. Based on the description of the core and the borehole, six types of facies were distinguished in the Nahr Umr Formation, resulting in an intercalated sandstone and shale with a thin layer of siltstone. The petrographic study of the clastic part of the Nahr Umr Formation showed that the sandstone is composed mainly of quartz arenite. Diagenesis processes affecting the Nahr Umr Formation are two types compaction and cementation processes. The sedimentary environment of the Nahr Umr Formation was represented by the deltaic fluvial environments. These environments appear in the central and southwestern parts of the study area. Sequence stratigraphy in the Nahr Umr Formation is beginning by sequence boundary type one (SB1) and sequence boundary type two (SB2) that appeared in the upper part of the formation. The other surfaces were represented by the end of the deposition of the Nahr Umr Formation and the emergence of the transgressive ravinement surface (TRS) within the transgressive system tract (TST)and The maximum flooding surface (MFS) was distinguished in the middle of the formation and each of these surfaces has a lateral extension along the study section. [ABSTRACT FROM AUTHOR]

Copyright of Spanish Journal of Palaeontology is the property of Socieadad Espanola de Paleontologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The discovery of Santonggou manganese deposit is an important breakthrough in manganese prospecting in East Kunlun. The detrital zircon from two siltstone samples of Santonggou manganese deposit were used for LA-ICP-MS U-Pb dating. The detrital zircon U-Pb ages are ranging from(1 497±17)Ma to(427±4)Ma, with two peaks of 441 and 473 Ma, respectively. The youngest detrital zircon age is(427±4)Ma, indicating the age of Santonggou manganese deposit is later than 427 Ma. The age peaks of detrital zircon are consisting with Early Paleozoic Naji Tal Group, and indicate that the detritals provenance are the middle strata of Naji Tal Group. The Re-Os isochron age of black shale from Santonggou manganese deposits are(387.4±6.2)Ma, indicating that the age of burial diagenesis is Middle Devonian, and the initial precipitation of manganese is earlier. Based on isotopic dating results, the sedimentary age of Santonggou manganese deposit is limited in Late Silurian-Middle Devonian. The relationship between the mineralization of Santonggou manganese deposit and the subduction of Proto-Tethys ocean is discussed based on the main view about genesis of Early Paleozoic marine sedimentary manganese deposit. It is considered that the subduction and closure of Proto-Tethys ocean in Early Paleozoic is the main reason for the mineralization of Santonggou manganese deposit, and the metallogenic age of Santonggou manganese deposit is basically consistent with the closure time of Proto-Tethys ocean. [ABSTRACT FROM AUTHOR]

The formation of oxalates in soils and rocks under conditions of cryoarid climate, permafrost and taiga vegetation was studied. Whewellite and weddellite were found in four areas associated with the mining industry: on the kimberlite deposit of the Daldyn territory, in the lower reaches of the Markha River of the Central Yakut Plain, and on the coastal outcrop of the Allah-Yun Sellah-Khotun ore cluster. Whewellite was found in the upper organic horizon of Skeletic Cryosol (Thixotropic) (sample 151) and as a film on the surface of plant remains of Humic Fluvisols (sample 1663). Weddellite was found as an extensive encrustation on the surface of the soil and vegetation cover of Stagnic Cryosols Reductaquic (sample 984) and on a siltstone outcrop (sample KM-6-21). Calcium oxalates were identified by X-ray phase analysis, photographs of the samples were taken on a polarizing microscope, and the crystal morphology was studied on a scanning electron microscope. To determine the chemical composition of soils and rocks, the classical wet-chemical method was used; the physical properties of the studied samples were studied using a pH meter, the photoelectric colorimetric method, and a synchrotron thermal analysis device. The source of calcium for the formation of salts is the parent layers of the studied soils, represented by carbonate and carbonate clastic rocks, which cause neutral and slightly alkaline environments. High humidity, which is provided by the seasonal thawing of the permafrost, has a key role in the formation of the studied oxalates in Yakutia with a sharply continental cryoarid climate. Based on the studies, it was found that the first two samples are the products of lichen activity, and the third and fourth are at the stage of initial soil formation by micromycetes. In addition, the formation of these oxalates, in our opinion, is the result of the protective function of vegetation, in the first two cases, with a sharp increase in the load on lichens under technogenic impact, and in the second and third cases, when favorable conditions arise for initial soil formation, but under conditions of toxic content of heavy metals and arsenic. [ABSTRACT FROM AUTHOR]

The purpose of this study was to identify the ostracod assemblage from a 43 m thick section of the Bizeljsko Formation, which constitutes the middle part of the Upper Miocene Posavje Group. The succession comprises sandstone, siltstone, and marlstone, deposited in a delta front environment. The determined ostracods belong to the families Cyprididae, Cytheridae, Darwinulidae, and Loxoconchidae. In total, 30 species were identified. Additionally, 8 morphotypes were determined at the genus level. The most common genera are Candona, Hemicytheria, and Cyprideis. The assemblage belongs to the Caspiocypris labiata subzone from the upper Pannonian. The ostracod assemblage from the Krsko Basin is similar in species composition to Pannonian ostracod assemblages from Croatia and Serbia. [ABSTRACT FROM AUTHOR]

The present study aims to investigate petrography characteristics and sedimental environments of upper Olenekian-middle Anisian deposits of Nakhlak group in the sedimentary-structural zone of central Iran. To this end, a section of these deposits with a thickness of 720 meters was first selected, and 190 samples were taken from this section for preparing thin sections. Also, quantitative and qualitative laboratory tests were performed and 25 samples of sandstone were selected for point counter analysis. The results indicated that the major deposits of this formation are related to siliciclastic, carbonate, and pyroclastic types, which are in the form of two facies associations. The facies association A at the bottom of the studied section with the thickness of 90 meters has a periodicity of clastic, carbonate, and pyroclastic facies. The clastic facies of this association consists of fine-grained sandstone. In addition, the carbonate facies in association A are characterized by two microfacies consisting of intraclast oolitic grainstone and oolitic grainstone. Further, tuffite is the only pyroclastic facies related to association A, which has a laminate structure, cross-bedding lamination, herringbone bedding, and upward-thinning and thickening cycles. The facies association, B which is deposited later, is more in the middle and top part of the section. The facies association B is 660 meters thick and has a periodicity of clastic and limestone facies. Clastic facies of this association includes four lithofacies such as conglomerate, pebble coarsegrained sandstone, medium-grained sandstone to thin layer siltstone and shale. The carbonate facies consists of four microfacies such as sandy intraclastic wackestone and mudstone. Furthermore, slumping structures, cross bedding, turbulence, boudinage structure, and convolute of sediments, along with the effects of erosional channels are observed in facies B. Field and laboratory studies conducted on this succession indicate the structure of facies association A was deposited in a mixed siliciclastic carbonate ramp. Finally, submarine canyons and submarine fan environments were left by increasing the depth of the facies association B in the deep part of sea and turbidity systems. [ABSTRACT FROM AUTHOR]

The Middle-Upper Eocene Hamra Formation, covering the northern plateau of the Bahariya Oasis, northwestern Desert, comprises two informal (lower and upper) members; the lower member (Upper Middle Eocene, 34.5-m thick) is made up entirely of fossiliferous limestone rocks (Nummulites gizehensis, Nummulites champolioni), while the upper member (Late Eocene, 38-m thick) consists of an intercalation of limestone with thin beds of sandstone, siltstone, and claystone. The upper member is highly fossiliferous with Turrittella, Carolia palcnoids, and Ostrea multicostata. Seven carbonate and three clastic microfacies have been recognized in five measured sections of the Hamra Formation. The carbonate microfacies were deposited on the proximal ramp setting of a warm and shallow sub-tropical environment. The lower member can be correlated with the (Upper Middle Eocene) Sath El Hadid and Fashn formations, while the upper member is correlated with the Upper Eocene Beni Sueif Formation. The reduced thickness of both members of the Hamra Formation compared with the corresponding rock units to the east reflects the structural uplift prevailed in the north of Bahariya Oasis during sedimentation. [ABSTRACT FROM AUTHOR]

Santonian-Campanian tuffaceous siltstone, epiclastic siltstone, arkose, and fossiliferous mudstone occur in a 45-m-thick section of well 1-BRSA-37-RJS drilled in the southern Campos Basin, offshore SE Brazil. Well log data and petrographic and lithogeochemical data obtained from cutting samples were used to propose a schematic model of the volcano's sedimentary paleoenvironment. The volcaniclasts in the tuffaceous siltstone and epiclastic siltstone are scoria basalts, typical of spatter cones associated with monogenetic fields worldwide. The combination of these features with the petrographic ones of the arkoses found in the same well interval is likely to be related to volcaniclastic processes taking place on the continental shelf. Ratios between the immobile trace elements of the volcaniclastic rocks can be explained by mixing between sources in the upper continental crust adjacent to southern Campos and the scoria basalts extruded in the monogenetic fields. The little differentiated, olivine-rich basalts extruded from the scoria and spatter cones suggest a rising asthenosphere mantle extending from hundreds of kilometers eastwards till southern Campos in the Santonian-Campanian. This may have resulted in regional discordances in the Santonian, both in the Campos and Santos basins, and also places the petroleum systems in the southern Campos Basin under the thermal influence of such a rising asthenosphere in the Santonian-Campanian. [ABSTRACT FROM AUTHOR]

San Cayetano Formation, of Lower Jurassic?- Upper Jurassic (Oxfordian) age, constitutes the oldest and most extensive stratigraphic unit in the Guaniguanico Mountain Range (western Cuba) and is part of: Alturas de Pizarra del Sur (APS) and Sierra del Rosario/Alturas de Pizarra del Norte/Esperanza (SR/APN/E), separated by carbonate sequences. Lithologically, it is composed by shale, siltstone and sandstone, in apparently monotonous and somewhat metamorphosed sections; towards the upper part limestone and conglomerate interbedding is reported. Information on mineralogical composition and sediments source area for sandstones has been limited. A review and reinterpretation of these rocks is carried out, with special attention to the petrographic characterization of quartz, lithoclasts, feldspars and zircon grains (with age reports from the Paleoproterozoic to early Devonian). As a result, it is found that the source area for these rocks classifies as from: internal craton and recycled orogens. Based on these results, and the report of a granitic intrusive recorded at site M0077A with an age of 326 ± 5 Ma (25 km from the Yucatan coastline), it is possible to specify some parts of the Maya block as the source area (northern part, currently under the Chicxulub impact structure and its coverage). It is also shown that the APS sequences resemble flood and shoreline sediments (predominance of pelites) while those of SR/APN/E are more varied: fan, slope and foot-slope sediments (sandstones predominate). [ABSTRACT FROM AUTHOR]

This article discusses the prospects for using large-format ceramic stones in the construction of contemporary homes, as well as an overview of raw materials and technologies for production. The most promising technology is stiff extrusion with the ability to load the raw products on firing trolleys and accelerate the processes of firing and drying. Characteristics of Eastern Donbass waste heaps processing screenings are given, which are coal mining by-products and are considered to be main raw material for the production of large-sized ceramic stone. It is shown that as a result of introduction of waste heaps into the production of ceramic stones with the lowest prime cost, the density of the resulting products will be less than 800 kg/m3, the thermal conductivity will be less than 0.20 m·°C/W, and the strength grade will be M150 and higher. Thus, the use of ceramic stones in total volume of wall products for residential construction will reach the level of 80% and will increase the competitiveness of the material, especially when compared with gas silicate products, as used in Western Europe. High economic feasibility of the production of such materials based on by-products of waste heap processing is shown as well. [ABSTRACT FROM AUTHOR]

Large earthquakes breaking the frontal faults of the Himalayan thrust system produce surface ruptures, quickly altered due to the monsoon conditions. Therefore, the location and existence of the Mw8.3 1934 Bihar–Nepal surface ruptures remain vividly disputed. Even though, previous studies revealed remnants of this surface rupture at the western end of the devastated zone, ruptures extent remains undocumented in its central part. Evidence for recent earthquakes is revealed along the frontal thrust in this region. The Khutti Khola river cuts an 8 m-high fault scarp exposing Siwalik siltstone thrusted over recent alluvial deposits, with faults sealed by a colluvial wedge and undeformed alluvial sediments. Detrital charcoals radiocarbon dating reveals that the last event occurred between the seventeenth century and the post-bomb era, advocating for the 1934 earthquake as the most recent event. In the hanging wall, fluvial terraces associated with fault scarps were abandoned after a penultimate event that happened after the tenth century, a rupture we associate with the historic earthquake of 1255CE. Slips of 11–17 m and 14–22 m for the 1934 and 1255 earthquakes, respectively, compare well with the ~ 10–15 m slip deficit accumulated between the two earthquakes, suggesting that most of the deformation along the front is accommodated by surface-rupturing earthquakes. [ABSTRACT FROM AUTHOR]

This study reports the detrital zircon U–Pb ages of the post collisional Chitarwatta Formation, exposed along the western margin of the Indian plate at the Sulaiman fold–thrust belt (SFB), Pakistan. The Chitarwatta Formation overlies the shallow marine carbonate sequence of the Kirthar Formation and represents an Oligocene–Miocene transitional marine sequence. The sequence consists of sandstone, siltstone, and mudstone. The sandstone consists predominantly (79–82%) of quartz grains. The framework grains are sub-angular to sub-rounded and show recycled orogenic provenance. The detrital zircon U–Pb age data show the dominant population between 390 Ma and ~1100 Ma, which is ~70% of the total population. In addition to this, a significant percentage of the younger detrital ages exist between ~40 Ma and ~120 Ma. This younger age cluster indicates the northern sources, including the Kohistan–Ladakh arc (KLA) and Karakoram block (KB), whereas the provenance for the 390–1100 Ma detrital zircon is likely the Higher Himalaya (HH), with contribution from Tethyan Himalaya (TH). This post-collisional scenario suggests that the Chitarwatta Formation received detritus from the northern sources through a drainage system, named as the Indus drainage system. A comparison with the coeval units in the north (Murree Formation, Dagshai Formation, and Dumre Formation) suggests that the sediments may have been delivered through the same drainage system that shares similar detritus. Relying on the contribution of the HH detritus, we propose that the HH uplifted during the Oligocene–Miocene along the Main Central Thrust (MCT) and provided detritus to the foreland basin. [ABSTRACT FROM AUTHOR]

The slurry–earth pressure balance dual-mode shield has an earth pressure balance (EPB) and slurry shield functions. Based on a shield tunnel project of Guangzhou Metro Line 12 in China, this study investigates the clogging prevention of a slurry–earth pressure balance dual-mode shield in a composed stratum with medium–coarse sand and argillaceous siltstone. The results show that the slurry mode was not applicable to the composed stratum with medium–coarse sand and argillaceous siltstone. The excavated soil accumulated easily in the slurry chamber, causing shield clogging. The total thrust force of the shield increased significantly, the tunneling speed gradually decreased to 0, and the torque of the cutterhead increased slightly after the slurry shield was clogged. The fluctuation in the total thrust force, the cutterhead torque, and the tunneling speed also increased significantly. The EPB mode is recommended for composed strata with medium–coarse sand and argillaceous siltstone. The dispersible foam agent and water needed to be used for soil conditioning. The injection amount of foam and water was determined according to the status of the mud discharged by the screw conveyor. Water absorption can be used to characterize the water absorption capacity of particles larger than 0.15 mm. The ideal soil state was that the consistency index of the particles smaller than 0.15 mm was less than 0.5 to prevent the EPB shield from clogging. The water absorption of soil with a particle larger than 0.15 mm should be removed when calculating the consistency index. [ABSTRACT FROM AUTHOR]

Compressive strength and tensile strength are the critical parameters to determine rock performance, which can reflect the rock's resistance to deformation and damage. Brazilian indirect tensile and uniaxial compression tests were carried out on rocks under different water immersion conditions to study acoustic emission (AE) characteristics and crack propagation during rock fracture. The test results show that water has a deteriorating effect on the argillaceous siltstone, with significant attenuation of both compressive and tensile strengths. With the increase in moisture content, the number of AE events decreased, the cumulative AE ringing count showed a gradual rise in steps, and the proportion of AE peak frequencies in the range of 0-200 kHz gradually increased. Natural rock samples are more brittle than water-saturated rock samples. The higher frequency of AE events and the higher energy released during the destruction of natural rock samples reflect in the clustering of high-energy AE source locus near the main rupture surface. The AE source locus is 1-2 energy levels higher in the vicinity of the fracture surface than in the water-saturated rock samples. The rock samples exhibited random packing of mineral particles and contained many clay minerals by SEM analysis of fracture microstructure. Water dissolves mineral particles and cementitious materials, producing microcracks with propagation potential. Analysis of the AE time sequence based on fractal theory reveals that fractal dimension value varies with the increase of moisture content. The variation of the fractal dimension D values for the water-saturated rock samples ranges from 0.4 to 0.65. This indicates that the number of microcracks is higher and their propagation more complex when the moisture content of the specimen is higher. The failure characteristics of the rock samples in the above research can provide a reference for monitoring rock mass stability under tunnel water inflow. [ABSTRACT FROM AUTHOR]

Ancient hydrocarbon-seep sites known as "Calcari a Lucina" are common in Miocene strata of northern Italy and typically consist of carbonate deposits dominated by large lucinid, bathymodiolin, and vesicomyid bivalves. Here we report two new sites found in Upper Miocene strata at Monte Mauro near Brisighella in the Emilia-Romagna province. One is unusual by being embedded in unconsolidated siltstone without any carbonate, but yet, consisting of the typical, seep-restricted bivalves Bathymodiolus moroniae and Archivesica aharoni vesicomyid clams and bathymodiolin mussels. The second deposit is dominated by the lucinid Megaxinus bellardianus, which has never been reported from a Miocene seep deposit in this region, despite being common in coeval siliciclastic sediments nearby. This species emphasizes biogeographic relationships between Upper Miocene seep faunas in the Mediterranean region and the tropic Indo-West Pacific Ocean. [ABSTRACT FROM AUTHOR]

The article presents the results of the research on mining production waste in the Chervonohrad Mining Area. For the first time the water extracts from certain types of waste rock, namely: burned and unburned argillite, siltstone, siliceous siltstone, coal, and sandstone were investigated. The studies covered the main chemical composition, as well as the pH and concentration of the main components of the aqueous extracts. Based on the obtained results, the properties of the investigated mining wastes were characterized, taking into account the impact on the environment. According to the obtained results, it can be stated that there is high content of Mg2+, SO42-, HCO3- in argillite and sandstone within the tericon of the central coal enrichment plant "Chervonohradska" and burnt argillite from the tericon of the Vizeyska mine. [ABSTRACT FROM AUTHOR]

Pipe jacking has been widely used in utility tunnel constructions as an environment-friendly method in China. This study is focused on the critical technologies used in the pipe jacking for the utility tunnel in Huanggang Mingzhu road. The inner and outer diameters of this utility tunnel are 4m and 4.8m respectively, which is the largest circular pipe jacking project in China at present. This utility tunnel is designed under the urban main road with heavy traffic, so the control accuracy of pipe jacking construction is required to be high. According to the characteristics of the project and actual construction technical measures, the key construction technologies including pipe jacking equipment selection, launching of small spacing, slurry circulating, drag reduction technology, and the control of surface settlement are discussed in this paper. Meanwhile, the jacking force and surface settlement during pipe jacking construction are monitored. The results show that the selected pipe jacking machine has good adaptability to the geological conditions of the project. The actual jacking force is much smaller than the theoretical value, and the two intermediate jacking stations are not activated. In addition, the road surface deformation is -8 -- 5mm during the whole process of pipe jacking construction, which has no impact on surface traffic. [ABSTRACT FROM AUTHOR]

The consideration of events of marine invasion within the continental Gondwanaland in the Indian subcontinent during the Permian is often doubted due to lack of appropriate fossil record. The Permian Barren Measures Formation within the Lower Gondwana Supergroup in eastern India is considered as deposited in a fluvio-marine estuarine setting, interpreted mostly based on sedimentological signatures in terms of marine tide and wave imprints within the so-called continental fluvial deposits. Fossilized shells of marine Gastropoda genus Baylea DeKoninck, 1883, are reported here from the siltstone beds of the prodeltaic sediments of the Barren Measures Formation, West Bokaro Basin. The in-situ preservation of the marine invertebrate fossils Baylea sp. provides definite proof of marine link of the West Bokaro Basin during the Barren Measures sedimentation. The present fossil record, when combined with sedimentological attributes, clearly signifies a marine inland encroachment event during the Permian time. [ABSTRACT FROM AUTHOR]

Joints and fissures in deep enclosing rocks impact the stability of the rock mass considerably. Therefore, understanding the deformation and damage mechanics of deep fissured soft rocks is crucial to ensuring the safety and efficiency of any project that involves them. Similar material testing is a commonly used method used to study rock strength and fissure evolution. In this study, we performed orthogonal tests to determine the similar material ratio of cement:sand:water:talc as 2:2.5:2:2 for the siltstone-like material found in the water-rich soft rock roadway enclosing rock in the fault fracture zone of the Hongqingliang coal mine. In addition, a fabrication method for prefabricated fissure specimens with appropriate water stability was designed based on sodium glutamate crystals. Subsequently, triaxial compression tests with high confining pressures were carried out on the prefabricated siltstone-like fissure specimens with different integrity indices. It was found that the peak stress of the specimens decreased with the decreasing integrity index, while the plasticity increased. As the integrity index decreases, the probability of decay in compressive strength also decreases, and the compressive strength shows a negative exponential correlation with the integrity index. The modulus of elasticity of the specimens at each integrity level shows varies directly with the confining pressure. In the case of a specimen with low integrity index, this phenomenon is obvious with certain fluctuations. Both Poisson's ratio and the internal friction angle show a good linear correlation with the integrity index, whereas cohesion shows a clear exponential decay trend. These results are of great significance in the study of rock strength damage and fissure evolution. [ABSTRACT FROM AUTHOR]

• Pressurized sealed shales were used to reveal in-situ oiliness and mobility. • TOC exhibits the opposite effects on the oiliness and mobility of shale oil. • The mobility of free oil is affected by adsorbed oil content and microcracks. • The movable threshold of free oil or OSI increases with increasing adsorbed oil content. Oiliness and mobility are key indicators to evaluate the sweet spots of shale oil. Due to the complex oil occurrence states and the lack of in-situ oiliness related experimental methods, the relationship between oiliness and mobility of shale oil is still unclear, which affects the evaluation of movable oil and the optimization of sweet spots. In this paper, the Upper Cretaceous Qingshankou Formation of lacustrine shale in the Changling Sag, the southern Songliao Basin is taken as the research object. Two-dimensional nuclear magnetic resonance (2D-NMR) experiments were performed on pressurized sealed cores before and after centrifugation to accurately characterize the effective porosity, oiliness, and oil mobility of shale reservoirs, these properties' international relationships and controlling factors were discussed, and then a suitable model for evaluating the movable oil was proposed. Based on 2D-NMR and pressurized sealed samples, shale in-situ oiliness can be accurately revealed, with a free oil content 2.48 times that of pyrolysis free hydrocarbons (S 1), which makes the previously used OSI (S 1 /TOC) calculated by pyrolysis S 1 unable to assess shale oil mobility. The correlation between effective porosity, oiliness, and oil mobility was better in siltstone and limestone interlayers and worse in shale reservoirs. Microcracks can significantly promote the mobility of shale oil, while adsorbed oil has the binding effect on the move of free oil, resulting in that shale oil can move until free oil or OSI reaches a certain threshold. The movable thresholds were redefined through the relationship between movable oil and free oil content, we found that as TOC or the adsorbed oil content increases, the movable thresholds for free oil and OSI also gradually increase, shale oils within different lithologies correspond to different movable thresholds, and using a fixed movable threshold for mobility discrimination will misjudge the sweet spots of shale oil interval. Based on the movable threshold of free oil, a model related to the maximum mobility of shale oil has been developed in this study, which has better applicability and is more accurate than the existing OSI method. The results of the present study are very important for deepening the understanding of the mobile mechanism and guiding the selection of sweet spots for shale oil. [ABSTRACT FROM AUTHOR]

• The strength effects under various cyclic loads were divided into low-stress weakening, low-cycle weakening, strengthening, and fatigue effects. • The correlation between the axial and circumferential ultimate strain, peak strength, and upper limit stress of cyclic load was established. • The mechanisms of rock strengthening and fatigue effects were revealed by AE energy and sources analysis. The purpose of this paper is to reveal the influence mechanism of various cyclic loads on siltstone strength, by conducting a series of coupled cyclic-monotonic loading tests. Firstly, it was found that the peak strength of rock depends on the upper limit and cycle number of cyclic load. The peak strength of siltstone shows low-stress weakening effect, low-cycle weakening effect, strengthening effect, chaotic effect, and fatigue effect. Secondly, the ultimate strain of siltstone under cyclic load is controlled by the peak strain of uniaxial compression test. The peak strength is linearly with the peak strain, and the peak strain under uniaxial compression can be regarded as the critical threshold for fatigue failure. Then, the decrease of AE b value reflects the aggregation of micro cracks, which can predict the damage and failure of siltstone earlier than the burst of AE signals. The propagation paths of cracks under these strength effects show significant differences, by comparing the evolution of three-dimensional AE sources with different energy levels. Finally, the fracture mechanism of the strengthening and weakening effects was discussed through electron microscopy scanning. The results indicate that the micro structures are adjusted by cyclic loadings, its fracture and energy release mode was changed, resulting in the increase of peak strength. [ABSTRACT FROM AUTHOR]

To quantitatively represent the deterioration law of the mechanical properties of siltstone after exposure to supercritical CO 2 (SC-CO 2), experiments were conducted to test the mechanical parameters of rocks under the coupling effect of CO 2 –water–rock interactions. The purpose of this study is to determine the evolution law and damage characteristics of each siltstone mechanical parameter under the action of SC-CO 2. In combination with numerical simulation results, this study revealed the damage evolution characteristics of rocks in a CO 2 geological storage reservoir. The research findings indicate that SC-CO 2 exhibits a certain time effect and causes non-uniform damage to siltstone. Both the deterioration law of the mechanical parameters and soaking time exhibited an exponential relationship. With increasing soaking time, both the uniaxial compressive strength and elastic modulus showed a decreasing tendency, whereas the Poisson's ratio showed a varying degree of increase. The total degree of deterioration gradually increased as the soaking time increased and approached a stable value. After exposure to SC-CO 2 , the damage deformation and failure mode transitioned from brittle to plastic in the siltstone samples. In addition, there was a shift from a single axial crack failure pattern to a complex failure mode with multiple cracks. This study also derived a uniaxial compressive strength prediction model for siltstone based on soaking time, constructed an elastic modulus damage model, and established a fluid–solid coupling model considering damage in the CO 2 geological storage process. The experimental and numerical simulation results revealed that microstructural alterations occurred in the siltstone after exposure to SC-CO 2. Furthermore, it was discovered that damage accumulation from the micro- to macroscale ultimately led to a gradual deterioration in mechanical properties. The research results provide a theoretical basis for mechanical stability evaluation in CO 2 geological storage. • By analyzing the peak stress evolution law of uniaxial loading failure of sandstone samples soaked in supercritical CO 2 , combined with the characterization results of sample failure modes, the uniaxial loading failure mechanism of sandstone considering the effect of soaking time was revealed. • Based on the degradation law of mechanical properties of sandstone after supercritical CO 2 immersion, a prediction model for uniaxial compressive strength and elastic modulus damage of sandstone based on immersion time were established. • A stress seepage damage coupling model for supercritical CO 2 geological storage was established, and the coupling relationship between reservoir stress and damage variables was analyzed, revealing the evolution characteristics of CO 2 geological storage reservoir damage. [ABSTRACT FROM AUTHOR]

Determining the transmission rate of radon gas in overburden strata is crucial for conducting a comprehensive study of radon gas's longitudinal and long-distance migration mechanisms. This study investigates the mineral components of rocks in the underground strata of the mining area using the X-ray diffraction method. Additionally, it examines the pore structure parameters of the rocks at different depths using the low-temperature nitrogen adsorption method. This research introduces an approach to inversion calculate the radon gas transmission rate through the activity ratio of radon's characteristic daughters based on the decay law and activity balance of 210Po and 210Pb daughters. In addition, it determines the transmission rates of radon gas in overlying strata at various depths through this method. The relationship between the rock's mineral composition and pore structure is investigated, and the effects of pore structure and mineral composition on the radon gas transmission rate are analyzed. The findings indicated that the pore structure exerts a dual impact on radon gas transport: macropores serve as channels for upward radon gas transport, while micropores offer most of the adsorption area. In contrast, the radon gas transmission rate is indirectly influenced by the mineral composition content associated with the medium's adsorption capacity and pore structure. In the studied lithologies, an increase in quartz content promotes radon gas transmission, while an increase in clay mineral content impedes it. Finally, the mechanisms of radon gas transport, daughter adsorption, and the impacts of rock pore structure and mineral composition on the radon transmission rate are discussed. [Display omitted] • The radon daughter measurement method that can effectively estimates the radon gas transmission rate was proposed. • How the pore structure and mineral components of rock in the underground strata affect radon gas transport rates. • The average radon gas transmission rate across different lithologies is siltite > shale > mudstone > sandstone > limestone. • An increase in quartz content promotes radon transport, while an increase in clay mineral content inhibits it. [ABSTRACT FROM AUTHOR]

Sedimentary rock deposits such as siltstone have been attracting interest due to their potential to store and control the movement of sequestered CO2. An understanding of weak caprocks is required to guarantee the safety of CO2 geo-sequestration projects where weak rocks are encountered. The cost and challenge of obtaining intact samples of weak caprocks from depths relevant to potential geo-sequestration targets has resulted in relatively little data on their mechanical behaviour being available. This paper describes the manufacture and characterisation of artificial siltstones, with properties typical of weak rocks, at stress levels relevant to geo-sequestration. It is shown that the artificial siltstones with properties typical of weak rocks can be simply produced from mixtures of sand, feldspar fines, plaster and water. [ABSTRACT FROM AUTHOR]

In order to extract gas accurately in Yue Nan coal mine and prevent gas over limit and gas accidents, a combination of theoretical analysis and numerical simulation was used to investigate the height of the overburden caving zone and fracture zone in the working face, using 215102 working face as the engineering background. The results show three key strata in the 215102 working face, namely siltstone, sandy mudstone, and sandy mudstone. The empirical formula's calculation results are in good accord with the findings of the theoretical analysis, which indicates that the height of the water-conducting fracture zone created by mining in 215102's working face is 87.35 m. The plastic zone, stress distribution and displacement variation of the model overburden of the working face were analyzed separately in the numerical simulation. The results of the plastic zone simulation show that the caving zone's maximum height is about 15.96 m, and the fracture zone's maximum height is approximately 82.39 m. The stress distribution shows that the caving zone's greatest height is around 13.65 m, while the fracture zone's maximum height is roughly 77.24 m. The amount of overburden subsidence proves that the caving zone's maximum height of about 10.08 m, and the fracture zone's maximum height of approximately 82.69 m. The height of the overburden caving zone and fracture zone of 215102 working face are ultimately found to be 14.02 m and 76.42 m, respectively, based on theoretical analysis, empirical formula calculation, and numerical simulation findings. [ABSTRACT FROM AUTHOR]

Proppant crushing and embedment in hydraulically-induced fractures is a major drawback to the recovery of unconventional oil/gas and geothermal energy production. This study provides a grain-scale analysis of the fracture evolution mechanisms of proppant crushing, rock fracture damage during proppant embedment, the influence of realistic reservoir/fracture fluid on proppant embedment, and the behaviour of proppant packs subjected to in-situ stresses using a discrete element modelling (DEM) approach. The results of this study reveal that the selection of an appropriate proppant type based on the nature of the reservoir formation plays a vital part in quantifying the degree of proppant crushing and embedment within fractures. The utilisation of frac-sand proppants instead of ceramic proppants in shallow soft sedimentary-based siltstone formations reduces proppant embedment up to 88%. However, whatever the depth of the fracture, the injection of ceramic proppants into granite-based geothermal formations is preferred to that of frac-sand proppants due to their lower proppant embedment and greater crush resistance. DEM analysis detected rock-spalling during the proppant embedment process, which ultimately led to the initiation of tensile-dominant secondary fractures in rocks. Fracture initiation, propagation, and coalescence during proppant crushing are analysed using calibrated DEM proppant-rock assemblies. Importantly, this study reveals that the saturation of formation rocks with fracturing/reservoir fluids may cause a significant increase in proppant embedment. Furthermore, proppant crushing, embedment, and re-arrangement mechanisms in proppant packs with different proppant distributions are analysed in this comprehensive numerical study. [ABSTRACT FROM AUTHOR]

Slope stability is the primary factor in designing a stable slope. The strength of the disposal slope relies on the characteristic of the dump materials. The rock shear strength denotes the rock's ability to withstand the burden, both constant and dynamic load. The weakest material used as a reference in designing the disposal slope is siltstone in Pulaubalang formation (location-04). The safety value in locations 04 and 02 tend to drop quickly as the inclination increase, while the safety in locations 01 and 03 tend to fall slowly. This indicates that rocks with a lower plasticity index tend to be stronger in steeper slope conditions. The slope geometry was designed to be 10, 15, 20, and 25 m high with a slope angle of 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, and 60° . The slope geometry is considered stable and safe. However, this study suggests that the most effective slope design is the slope with 25 m high, an overall slope of 25.3° ; a single slope of 35° ; a berm width of 4.66 m, bench height of 5 m, with a safety factor value of 4.30 (SF= 4.30). [ABSTRACT FROM AUTHOR]

The paper presents results of modeling the chemical interactions of Quaternary meteoric waters with siltstones of the upper part of the Vendian Padun Formation of the Mezen Syneclise, Arkhangelsk region, Russia. Equilibrium and equilibrium-kinetic approaches were applied. It is shown that under conditions of intensive water exchange and low temperature, due to low rates of interaction of minerals with water, the redox buffer of rock-forming minerals at this stage of the process makes a subordinate contribution to the dissolution of uranium. Therefore, for a sufficiently long time, the main agent of mobilization of uranium in rocks is oxygen dissolved in water. [ABSTRACT FROM AUTHOR]

This manuscript pivots around the durability results at the laboratory scale for the rocks of the sub-Himalayas. The sedimentary origin rocks of sub-Himalayas comprising sandstone, siltstone, claystone, mudstone, and silt-shale induce weathering-based failures in the cut and natural slopes. The higher weathering/slaking rates of incompetent lithologies such as claystone and mudstone cause failures in overlying competent sandstone/siltstone/silt-shale, units. During the geotechnical investigations, defining the descriptive categories of the rocks with any classification is the initial step. Slake Durability Tests are commonly used to classify and characterize clay-bearing rocks. This research utilized three different durability-based systems, and rocks were characterized. These classification systems are based on the slake durability index, disintegration ratio, and relative slake durability index. The research concludes that the relative slake durability classification over-estimates the durability of the rocks. This manuscript also concludes that a durability-based classification and detailed investigations should also be initiated for the sub-Himalayan region. [ABSTRACT FROM AUTHOR]

Due to the transfer of Lannigou gold mining from shallow to deep, a series of stability problems of surrounding rock have been caused. The drilling pressure relief technology has unique advantages in the control of mine pressure in high-stress roadways. In order to explore the damage effect of borehole pressure relief technology on rock, uniaxial compression and acoustic emission tests were carried out on siltstone specimens with borehole diameters of 8 mm, 12 mm, and 16 mm, respectively, and the acoustic emission signals of the whole process were collected simultaneously to explore the uniaxial compression of siltstone specimens with prefabricated holes in this paper. According to the statistical characteristics of acoustic emission, the damage law of siltstone specimens with prefabricated holes was explored from the microscopic point of view and the damage effect of drilling on siltstone specimens reflected by the acoustic emission phenomenon was revealed. The research results show that there are multiple stress drops before the deformation and failure of the rock sample with prefabricated drill holes; there is a positive correlation between the diameter of the drill hole and the power law index of the stress drop distribution; the acoustic emission activity of the rock during the deformation and failure process can be indirectly reflected the evolution of microfractures; the energy probability density function under different borehole diameters conforms to the power law distribution; the critical exponent obtained by the maximum likelihood estimation has an optimal plateau value, which can accurately characterize the power exponent of the energy distribution; the launch waiting time and aftershock sequence have a good power-law distribution in logarithmic coordinates. The research results provide a certain theoretical basis for the application of drilling pressure relief technology in southwestern Guizhou. [ABSTRACT FROM AUTHOR]

In order to study the weakening mechanism of mechanical properties and the evolution of fracture of water-bearing rocks, cylindrical standard siltstone samples with four moisture contents (0, 2.85, 3.87, and 4.25%) were prepared, and the mechanical properties, damage mode, AE characteristics, and fractal law of water-bearing rock samples were studied by means of uniaxial compression test and acoustic emission (AE) monitoring technique, and based on the test findings, a constitutive model of the entire process of rock deformation and damage under uniaxial compression was built with different moisture content of rock. The results show that with the increase of moisture content, the peak stress, the stress threshold of void compaction stage, and the stress threshold of elastic stage of the rock samples decreased linearly, elastic modulus decreased exponentially as a function, and the peak strain, the strain threshold of void compaction stage, and the strain threshold of elastic stage increased linearly. The higher the moisture content, the weaker the AE signal intensity and the smaller the AE count value. From dry to saturated, the damage form of rock samples gradually transitioned from predominantly tensile damage to predominantly shear damage. The fractal dimension of the broken block linearly decreases as the moisture content rises. The model constructed in this paper has good applicability to the deformation characteristics of water-bearing rocks under uniaxial compression before the peak stress; it especially can express the rock void compaction stage, but it cannot accurately describe the postpeak deformation characteristics. [ABSTRACT FROM AUTHOR]

In this paper, the mechanical behaviors of different lithological rocks of coal measure strata from Shanxi Formation in the eastern margin of the Ordos Basin, China, were investigated through uniaxial compression tests, and the deformation characteristics and failure modes of different lithological rocks were investigated. On this basis, the energy evolution of different lithology rocks was also discussed. The results show that there are obvious differences in the mechanical properties of different lithology rocks in coal measure strata, resulting in different wellbore instability prevention measures and fracturing measures in different lithology strata. Under the uniaxial compression condition, the peak strain of different lithological rocks is obviously different, and the denaturation characteristics are also obviously different, and the failure modes of rocks are mainly the tensile fracture mode, suggesting that the rock samples have strong brittle characteristics. With the increase of the strain, the total energy of different lithological rocks of the coal measure strata increases, and the elastic energy first increases and then decreases rapidly, whereas the dissipated energy first increases slowly and then increases rapidly. Each energy at the peak point is different, and the average total energy of shale, silty shale, siltstone, fine sandstone, and coal is 0.022 J/cm3, 0.045 J/cm3, 0.052 J/cm3, 0.042 J/cm3, and 0.003 J/cm3, respectively, indicating that there are obvious differences in the energy evolution laws of the different lithological rocks. [ABSTRACT FROM AUTHOR]

An accurate understanding of how water can affect the time-dependent deformation is important to assess the long-term stability of geotechnical projects. Triaxial compression rheological tests with different water contents were carried out to investigate the effects of water content and stress level on the creep strain, creep rate, long-term strength, and creep failure mode. Our experiments show that the time-dependent characteristics of rock are gradually activated with the increase of water content and stress level. The water content and stress level greatly increase the instantaneous strain, creep strain, and the steady creep strain rate, however, shorten the time to dilatancy and the time to failure. The creep curves and the creep rate versus time curves of argillaceous siltstone in the accelerated creep stage show a trend of "brittle-to-ductile" transformation. A modified steady-state creep rate tangent method was proposed and the analysis proves that the long-term strength of the rock decreases continuously with increasing water content. With the increase of water content, the rock exhibits a regularization of the main fracture surface, a gradual decrease of the number of secondary cracks, and a gradual disappearance of the shear slip phenomenon as observed. Our explanation is that since the clay minerals of T3sn argillaceous siltstone are mainly kaolinite, the main softening mechanism of the rock at low water content (0 ~ 1.14%) is the lubricating effect of the bound water film. The softening mechanism of clay-rich siltstone at high water content (1.14–3.35%) is dominated by the hydraulic fracturing action of pore water and Rehbinder effect. Highlights: The triaxial compression creep properties of argillaceous siltstone with different water contents are exposed. A modified steady-state creep rate tangent method for the determination of the long-term strength of soft rocks such as argillaceous siltstone is proposed. The softening mechanism of clay-rich siltstone with different water contents is analyzed and revealed. [ABSTRACT FROM AUTHOR]

Enclaves constitute a key tracer guide to assess the magmatic source and evolutionary processes of Cu–Mo–Au porphyry-type deposits. In this study, four types of enclaves were identified in the Baogutu reduced Cu porphyry-type deposit, West Junggar, Northwest China: gabbroic enclaves (Type 1) and schist enclaves (Type 2) are proposed to be restites and immiscible enclaves, respectively, which confirm the contributions of mantle components and sediments in the reduced Cu porphyry-type deposit. Fine-grained dioritic enclaves (Type 3) have a similar mineral composition and texture to the dioritic host rocks, which are probably autoliths derived from inhomogeneous fractional crystallization. Tuffaceous siltstone enclaves (Type 4) with a zircon U-Pb age of 339.2 ± 7.5 Ma (MSWD = 0.55), the formation age of which is in agreement with the host early Carboniferous rock unit, indicate that these tuffaceous siltstone enclaves might have formed in a contamination process. Moreover, the schist enclaves, together with the newly discovered 2691.3 ± 12.3 Ma inherited zircon in tuffaceous siltstone enclaves, further indicate that the Baogutu arc could be a continental arc. [ABSTRACT FROM AUTHOR]

The traditional grouting support technology presents fatigue and failure during the process of excavation of underground works passing through water-rich soft rock. Based on the above idea, a new grouting reinforcement method, "self-solution grouting reinforcement method," is proposed in this paper. The method uses the surrounding rock water body as the hydrolysis and transportation medium of cement, and realizes slurry diffusion through the circulation of water system in the surrounding rock. This paper independently designed the self-dissolved grouting reinforcement indoor test device through continuous debugging and optimization, which can meet the requirements of the indoor test. The feasibility and mechanism of the self-dissolved grouting reinforcement method are explored and studied by laboratory test. Four kinds of consolidation bodies were obtained by self-dissolving grouting and traditional grouting on water-rich broken argillaceous siltstone and granite, and the mechanical properties of the grouting solid are compared and analyzed. It is found that the effect of self-dissolution grouting method in the water-rich soft rock like argillaceous siltstone is obviously better than that of traditional grouting method, and the uniaxial compressive strength and the elastic modulus are increased obviously. [ABSTRACT FROM AUTHOR]

Fossil remains of chondrichthyan tooth bases (roots) were found in Lower Permian beds exposed along the forest road between Dovje and Plavški Rovt. These layers are part of the clastic development of the Trogkofel Group beds. They are composed of an alternation of dark to light-grey shales, siltstone, and sandstone with rare beds of the conglomerate. Within the clastic succession, layers or lenses of dark-grey to black limestones (biosparitic, biomicritic and oolitic) and limestone breccias occur. The limestone consists remains of algae, fusulinids, brachiopods, and mostly crinoids (Palermocrinus and Entrochus). Detail study has shown that two remains of tooth bases belong to the genus Petalodus, one of them to the species Petalodus ohioensis. The bases are tongue-shaped and come to a rounded point in the distal (base end) edge. On the surface of the base, the typical oval-shaped foramina are visible. In addition, the osteodentine is visible on the cross-section of one specimen. Teeth of Petalodus are often the most common chondrichthyan fossil vertebrate remains reported from the Carboniferous and Permian rocks of the USA, Europe, and Russia. In Slovenia, Petalodus ohioensis has been recorded only from Upper Carboniferous beds. The new record of Lower Permian remains contributes to the knowledge of this cosmopolitan but still common genus of Late Paleozoic chondrichthyans. [ABSTRACT FROM AUTHOR]

Red-bed argillaceous siltstone is a common soft rock in the drawdown area of water diversion project extending from the Yangtze to Huaihe Rivers, with the characteristics of water softening and disintegration, which directly threatens the stability and safety of the diversion project. To better understand the effect of cyclic drying–wetting on the disintegration characteristics and mechanism, disintegration experiments were conducted on the red-bed argillaceous siltstone from the Tongcheng area of the water diversion project extending from the Yangtze to Huaihe Rivers. Experimental results indicated that, with an increasing number of drying–wetting cycles, the red-bed argillaceous siltstone was gradually crushed, large particles gradually transformed into small particles. A microstructural analysis showed that a continuous drying–wetting process resulted in the sample surface becoming disordered and complicated, and new micro-fractures and pores were generated. Notable changes in the concentrations of ions in the soaking solutions indicated continuous dissolution of the minerals, and a large amount of mineral loss under the action of cyclic drying–wetting. Furthermore, the evolution of disintegration parameter further indicated that the disintegration of red-bed argillaceous siltstone was gradually intensified by the increasing number of drying–wetting cycles. The fractal dimension D and the incremental surface energy gradually increased with an increase in the number of drying–wetting cycles. Thus, the proposed energy dissipation model effectively describes the disintegration characteristics of red-bed argillaceous siltstone under the cyclic drying–wetting, and thus, it can be used to guide engineering practices. [ABSTRACT FROM AUTHOR]

Lower and middle Cambrian strata of the eastern Mackenzie Mountains, Northwest Territories, Canada, were deposited in a semi-enclosed basin along the eastern flank of the Mackenzie Arch. The Mount Clark Formation is predominantly composed of nearshore sandstone and is overlain by deeper water siltstone, mudstone, and carbonates of the Mount Cap Formation. The contact between these formations is interpreted as a flooding surface. Trilobite biostratigraphy indicates the presence of the traditional upper Olenellus through Glossopleura zones (Cambrian Series 2, Stage 4–Miaolingian, Wuliuan) and suggests the flooding surface is diachronous, spanning the Dyeran-Delamaran boundary. Above the Olenellus Zone, the Amecephalus arrojosensis-Eokochaspis nodosa Zone, the new Aitkenaspis keelensis Zone, the new Albertelloides mischi Zone, and the Glossopleura walcotti Zone are recognized. Whereas the older zones are comparable to those in other areas of Laurentia, the trilobite faunas in the Albertelloides mischi and Glossopleura walcotti zones show a greater abundance of zacanthoidids and dolichometopids. They also have a lower diversity of ptychoparioids and oryctocephalids, and lack agnostoids, eodiscoids, dorypygids, and ogygopsidids. This suggests that zacanthoidids and dolichometopids were able to tolerate conditions that were unfavorable to the other groups, probably related to semi-restricted conditions in the basin. Four endemic species exhibit characteristics that are considered paedomorphic. This developmental process took place in three separate lineages, suggesting that heterochrony was also environmentally provoked. New taxonomic names are authored by Handkamer and Pratt. New genera are Eobathyuriscus, Sahtuia, Mexicaspidella Aitkenaspis, Dodoella, and Mackenzieaspis. New species are Bolbolenellus dodoensis, Eobathyuriscus mackenziensis, E. macqueeni, Glossopleura youngi, Sahtuia carcajouensis, Aitkenaspis keelensis, Albertelloides eliasi, Dodoella kobayashii, Mackenzieaspis parallelispinosa, and M. divergens. UUID: http://zoobank.org/a10a2470-853c-4ce8-bf62-7de1d2c99fab. [ABSTRACT FROM AUTHOR]

Characterization of reservoir petrophysical properties provides critical insights into reservoir deliverability and field development strategy. The main objective of this work is to present a comprehensive core-based petrophysical assessment of the Cenomanian Bahariya Formation and the Turonian Abu Roash (AR-D and AR-E, respectively) Members of the Abu Gharadig field situated in the Western Desert, Egypt. The AR-D is water-wet and consists of micro- to mesoporous shallow marine limestone lithofacies with moderate porosity (Φ), poor horizontal permeability (Kh) with poor permeability anisotropy due to the presence of vertical fractures, while the nano- to mesoporous argillaceous limestone lithofacies is very tight. Both the lithofacies exhibit primary and secondary depositional fabrics. Overall, the AR-D member exhibits impervious to poor reservoir quality, and so a suitable stimulation strategy will be essential to produce from this interval. The AR-E interval implies a tidal depositional environment. The calcareous sandstone lithofacies of the AR-E is macro- to megaporous and exhibits moderate to high porosity (> 15%) and excellent permeability (up to 305 mD). The meso- to microporous glauconitic siltstones of the AR-E have poor porosity and permeability. Both lithofacies are characterized by high water saturation, preserve primary depositional fabrics and consist of isotropic pore system along with some connected horizontal pores yielding higher permeability anisotropy. The Bahariya Formation consists of fine to medium grained massive sandstone lithofacies with minor siltstone intercalations, indicating a channel deposit in a coastal or fluvio–deltaic environment. It exhibits high porosity (~ 20%) and permeability (up to 649 mD) but shows very high water saturation. It preserves the primary depositional fabrics with isotropic pore system. The thin siltstone intercalations may act as vertical barriers. Based on the petrophysical assessment, we made recommendations on the reservoir development aspects. [ABSTRACT FROM AUTHOR]

The formation of oxalates in soils and rocks under conditions of cryoarid climate, permafrost and taiga vegetation was studied. Whewellite and weddellite were found in four areas associated with the mining industry: on the kimberlite deposit of the Daldyn territory, in the lower reaches of the Markha River of the Central Yakut Plain, and on the coastal outcrop of the Allah-Yun Sellah-Khotun ore cluster. Whewellite was found in the upper organic horizon of Skeletic Cryosol (Thixotropic) (sample 151) and as a film on the surface of plant remains of Humic Fluvisols (sample 1663). Weddellite was found as an extensive encrustation on the surface of the soil and vegetation cover of Stagnic Cryosols Reductaquic (sample 984) and on a siltstone outcrop (sample KM-6-21). Calcium oxalates were identified by X-ray phase analysis, photographs of the samples were taken on a polarizing microscope, and the crystal morphology was studied on a scanning electron microscope. To determine the chemical composition of soils and rocks, the classical wet-chemical method was used; the physical properties of the studied samples were studied using a pH meter, the photoelectric colorimetric method, and a synchrotron thermal analysis device. The source of calcium for the formation of salts is the parent layers of the studied soils, represented by carbonate and carbonate clastic rocks, which cause neutral and slightly alkaline environments. High humidity, which is provided by the seasonal thawing of the permafrost, has a key role in the formation of the studied oxalates in Yakutia with a sharply continental cryoarid climate. Based on the studies, it was found that the first two samples are the products of lichen activity, and the third and fourth are at the stage of initial soil formation by micromycetes. In addition, the formation of these oxalates, in our opinion, is the result of the protective function of vegetation, in the first two cases, with a sharp increase in the load on lichens under technogenic impact, and in the second and third cases, when favorable conditions arise for initial soil formation, but under conditions of toxic content of heavy metals and arsenic.

The separation and investigation of plastic dissipation energy and damage dissipation energy, and the exploration of the association between energy dissipation and crack development, contribute to revealing the essence of rock failure. In this study, triaxial cyclic loading and unloading tests were performed on porous siltstone widely distributed in mining areas in western China. According to the characteristic stresses and energy evolution characteristics, the failure process of siltstone was divided into five stages. The cumulative energy dissipation ratio shows a spoon-shaped evolution characterized by a significant decline, slight decline, slow increase, significant increase, and stable trend. Importantly, a method for separating plastic dissipation energy and damage dissipation energy was proposed and applied to investigate the evolution characteristics of plastic dissipation energy and damage dissipation energy. Corresponding to the energy characteristics, the acoustic emission activity exhibits significant phased characteristics in five stages. Furthermore, the analysis of crack evolution based on acoustic emission parameters reveals that the proportion of tensile cracks increased significantly near peak failure, and the development of tensile cracks substantially contributed to the damage of load-bearing structures. In particular, the evolution of shear cracks exhibited a strong correlation with the cumulative plastic dissipation energy, while the evolution of tensile cracks showed a strong correlation with the cumulative damage dissipation energy. Finally, the energy dissipation mechanisms of tensile cracks and shear cracks were revealed.Highlight [ABSTRACT FROM AUTHOR]

Oil migration in shale formations across multiple scales from nanometers to meters, a topic without receiving sufficient attention, is of great significance to the accumulation and production of shale oil. Compared with oil migration in conventional reservoirs usually with a long distance, shale oil migration is much shorter, which challenges the applicability of conventional characterization methods for shale formations. In addition, shale oil migration in different types of shale formations occurs at different scales, and their source-reservoir configuration, accumulation mechanism, and exploration plans are also different, greatly complicating a cost-effective and sustainable exploitation of shale oil resources. Accordingly, this review summarizes the experimental methods for characterizing the shale oil migration across multiple scales, and reveals the migration characteristics in three different types of shale oil formations of typical basins in China and USA. The shale oil migration distance in "pure shale-type" formation is the shortest and mainly in nanometer-microns scale. The migration characteristics of "pure shale-type" shale oil are difficult to reveal directly due to its ultra-short migration distance, which may be indicated by the microscale compositional changes at the surface of minerals being interacted with organic fluids and requires additional innovations on the shale oil migration characterization methods with a high accuracy. The shale oil migration distance in laminated-type shale oil formation is at the lamina (micron-millimeter) scale and the shale oil migrates from the organic matter-rich to -lean laminae. The lamina type (felsic, carbonate, or clayey) significantly affects the migration and enrichment of shale oil by providing different types of pore spaces and migration pathways. The shale oil "composition change" method effectively indicates the migration characteristics of shale oil among different laminae, while the "hydrocarbon expulsion efficiency" method is not accurate for the laminated-type shale oil. The migration distance of sandwich-type shale oil is at the millimeter-meter scale, which is the largest among three types of shale oil formations. The reservoir space is mainly intergranular pores and the shale oil migrates from the overlying or underlying organic matter-rich shale to the siltstone interlayer. Both "hydrocarbon expulsion efficiency" and "composition change" methods can be used to clarify the migration characteristics of sandwich-type shale oil. This review overall has a great significance for deeply understanding the characterization methods and migration characteristics of different types of shale oil formations at multiple scales. [ABSTRACT FROM AUTHOR]