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The Guxiang–Tongmai segment of the Jiali fault is situated northeast of the Namche Barwa Syntaxis in northeastern Tibet. It is one of the most active strike‐slip faults near the syntaxis and plays a pivotal role in the examination of seismic activity within the eastern Himalayan Syntaxis. New study in the research region has yielded a 1:200000 gravity dataset covering an area 1500 km2. Using wavelet transform multiscale decomposition, scratch analysis techniques, and 3D gravity inversion methods, gravity anomalies, fault distributions, and density structures were determined across various scales. Through the integration of our new gravity data with other geophysical and geological information, our findings demonstrate substantial variations in the overall crustal density within the region, with the fault distribution closely linked to these density fluctuations. Disparities in stratigraphic density are important causes of variations in the capacity of geological formations to endure regional tectonic stress. Earthquakes are predominantly concentrated within the density transition zone and are primarily situated in regions of elevated density. The hanging wall stress within the Guxiang–Tongmai segment of the Jiali fault exhibits a notable concentration, marked by pronounced anisotropy, and is positioned within the density differential zone, which is prone to earthquakes. [ABSTRACT FROM AUTHOR]

Geologic carbon sequestration requires CO2 injection into the storage formation at high‐injecting pressure. Such high pressure could induce choked flow accompanying huge variations in thermodynamic properties of CO2 at a converging‐diverging (CD) fractures in the storage formation. In this study, high‐velocity CO2 transport through CD fractures was investigated to quantify the effect of fracture morphology on occurrence of both choked flow and shockwave that constrain the mass flow rate of fluid. In addition, variations in thermodynamic CO2 properties including Mach Number (Ma), defined by the ratio of fluid velocity to sound speed, and shock properties were investigated. The morphological characteristics of CD fractures were determined by nine properties, such as throat diameter, throat length, inlet diameter, outlet diameter, throat diameters of two‐connected CD fractures, fracture wall curvature, roughness amplitude, and frequency. As a result, the throat diameter crucially affected choked flow occurrence and maximum Ma. When the inlet and outlet diameters varied, the profiles for Ma variation were consistent in the converging and diverging segments, respectively. In addition, regardless of change in the throat length, the position of maximum Ma was nearly constant with showing the position length ratio of 0.13–0.14. However, roughness of fracture wall significantly influenced the Ma variation and occurrence of shock. In particular, backflows segregated from the main CO2 flow were observed near the wall roughness. Plain Language Summary: Choked flow is a fluid‐mechanical process that restricts the mass flow rate of fluid and it can be occurred when fluid velocity overcomes its sound speed. When CO2 is injected into the targeted geologic formation, choked flow can occur due to highly pressurized flow within the fractures located near the CO2 injection well. Once choked flow occurred, the shock, which accompanies substantial changes in the thermodynamic properties of CO2, follows in the fractures. In the study, choked flow is generated within the converging‐diverging (CD) fracture which serves as a pathway of injected CO2, and its cross‐sectional area decreases and increases again after the "throat." We assumed that the CD fractures have various morphologic properties and analyzed the relationship between the fracture morphology and shock properties. The results highlighted that the throat diameter and fracture roughness mainly affected choked flow occurrence and shock properties. Findings here are applicable to other site‐specific studies, such as volcanoes, geysers, geothermal fields, and underground hydrogen storage sites where highly compressed fluid often migrates through subsurface fractures or any types of geologic conduits. Key Points: CO2 flow within the fracture was simulated to evaluate the effect of fracture morphology on choked flow and shock generationMorphologic properties including throat diameter and length, inlet and outlet diameter, number of throats, and wall roughness were variedThroat diameter influenced the Mach number (Ma); a complicated trend of Ma and backflow were observed owing to wall roughness [ABSTRACT FROM AUTHOR]

Anomalous solute migrations in fractured rocks are governed by geometric characteristics and flow regimes. Although existing inverse models can describe this behavior, the underlying physics for quantifying key transport coefficients remains largely unexplored. Here, we investigate the quantitative impacts of geometric heterogeneity and flow regimes on solute transport in rock fractures. We conduct numerical experiments to simulate water flow and conservative solute transport in 3D fractures with varying geometric features and Reynolds numbers. Our results show that the non‐Fickian transport is prevalent across the entire flow regime, with Darcy flows attributed to geometric heterogeneity and non‐Darcian flows influenced by additional eddy zones. We employ the mobile‐immobile (MIM) domain model and continuous time random walk (CTRW) model to inversely model simulated breakthrough curves. Inverse analyses demonstrate that both models effectively characterize anomalous transport behaviors. The fitted transport coefficients of the MIM model exhibit stronger quantitative relationships with aperture and roughness parameters, as well as Reynolds number, compared to the CTRW model. By incorporating parameterized transport coefficients, we propose physics‐ and statistics‐based models to directly predict anomalous transport behaviors under different flow regimes. These prediction models accurately reproduce solute transport processes of all simulated cases with acceptable errors. The feasibility of directly predicting solute transport under varying flow regimes using geometric information is thus validated. Our study not only supports the study of substance migration based on geometric structure features, but also serves as a foundation for investigating geological activities based on substance migration information. Plain Language Summary: The migration of substances within geological formations is governed by their geometric pore structure, while information about substance migration can reveal the geometric characteristics of these formations. In this context, these two aspects form an interdependent feedback system. Investigating quantitative relationships and models between the geometry of geological formations and substance migration is thus crucial for understanding various geological processes related to geometric structure changes and hydrogeochemical signals (i.e., chemical information carried by groundwater or surface water, which reflects various natural and anthropogenic geological processes) evolution. Here, we explore the impact of both geometric structure and hydrodynamic conditions on solute transport in rock fractures. We conduct extensive direct numerical simulations to determine the inherent quantitative relationships between key transport coefficients and geometric parameters under different flow regimes. Based on these relationships, we establish upscaling models for directly predicting solute transport processes using only geometric parameters within both physics‐ and statistics‐based frameworks. This research has significant implications for predicting solute migrations using measurable physical properties and offers potential applications for studying geological activities related to fractured rocks through analyzing released hydrogeochemical signals. Key Points: Non‐Fickian transport behaviors in 3D fractures under different Re were characterized within physics‐ and statistic‐based frameworksTransport coefficients within mobile‐immobile and continuous time random walk frameworks were systematically parameterized by geometric and hydrodynamic parametersDirectly predicting solute transport via geometric parameters under different Re is feasible in both physics‐ and statistic‐based frameworks [ABSTRACT FROM AUTHOR]

Study of inclusions in gems from secondary deposits can give valuable clues on the geologic (and sometimes geographic) origin of these displaced materials. For the present study, seven gem quality fancy‐coloured sapphires from Songea, Tanzania, were selected with, rarely observed in these gems, garnet inclusions in order to better understand their formation. Therefore, Raman spectroscopy was used to study garnet, as well as rutile, aluminosilicate and mica inclusions. Garnet composition calculations were made using the MIRAGEM Raman spectra software, which was further improved for the purpose of this study. A couple of garnet inclusions were also analysed by energy dispersive X‐ray spectroscopy (EDS) attached to a scanning electron microscope (SEM). All garnet inclusions presented similar Raman spectra, thus similar chemical composition. Chemical analysis demonstrates that these are pyrope‐rich (>40%) garnets with over 30% of almandine and over 20% grossular without any detectable titanium, chromium and sodium. Calculations made using the updated/improved MIRAGEM software were able to indicate the same composition as compatible with the obtained chemical analyses. Muscovite and sillimanite were also identified using micro‐Raman spectroscopy. This inclusion scene is not similar to those described in fancy‐coloured gem sapphires from other localities. The exact geological formation of these gems is yet not understood but might be eclogite or upper mantle related. [ABSTRACT FROM AUTHOR]

Aim: Adaptation to local environments has been considered a driving force of ecological speciation. Previous phylogenetic studies at higher taxonomic levels have strongly suggested that herbivore diversification occurs through local adaptation to host plants. However, whether similar mechanisms contribute to within‐species diversification remains poorly understood. We reconstructed species expansion processes using the phylogenetic relationships between two Luehdorfia butterflies and their host plants and tested the local adaptation hypothesis during species diversification. Location: Japanese archipelago. Taxa: Luehdorfia japonica and L. puziloi. Methods: We analysed mitochondrial DNA and single‐nucleotide polymorphisms to trace the expansion processes of two species in the Japanese archipelago. We analysed data collected during trans‐host plant feeding experiments to test for local host plant adaptation in L. japonica. Results: Luehdorfia japonica differentiated 17.0 million years ago (MYA) from a group of four Luehdorfia species in East Asia, and L. puziloi differentiated 13.3 MYA from the remaining three species. We observed several genetic groups in both species, reflecting geographical differences among populations. Some host plants had detrimental effects on the pupation rates of L. japonica, demonstrating the presence of genetic barriers between populations of this species. Main Conclusions: Although these two sibling species were influenced by the geological formation of the Japanese archipelago, their present population structures differ greatly: L. japonica expanded its distribution and adapted to local host plants along at least four expansion routes independent of host plant phylogeny, and L. puziloi exhibited a more isolated population structure and was less strongly influenced by gene flow among populations. These results suggest that both isolation by distance and isolation by adaptation have been important drivers resulting in the present‐day population structure of L. japonica. Unidirectional gene flow through local adaptation to the host plant may have played a role in initial speciation. [ABSTRACT FROM AUTHOR]

In this paper, we present the first results obtained after new fieldwork and laboratory studies of chert catchment sources during the Middle and Upper Palaeolithic in inland Iberia, a region that has been traditionally depicted as marginal and sparsely populated during the last glacial due to its harsh ecological conditions compared to the coastal areas of the Iberian Peninsula. Our main aim is to determine the mobility strategies and social networks of the last Neandertals and first modern humans settled in inland Iberia and neighbouring regions, and eventually test the hypothesis that the last glacial human settlement in the Iberian hinterland was more dense and complex than previously thought. In this study, we focus on the cherts exploited at two archaeological sites: the Peña Cabra and Peña Capón rock shelters. These sites are located in the southeastern foothills of the Central System range, in the province of Guadalajara (Spain), and they have yielded a sequence of human occupations from the Middle and Upper Palaeolithic, respectively. To obtain a detailed picture of the mobility patterns and catchment strategies of the hunter‐gatherers settled at these sites, our fieldwork focussed on identifying chert outcrops that could have been frequented and exploited by them. After two field seasons, 22 chert outcrops from eight geological formations were identified and more than 300 samples were collected and analysed. We conducted textural, micropalaeontological, petrographical and geochemical analyses, with the aim of comprehensively characterising the various rock resources available in the study area. Results have shown that different siliceous varieties were available in the area surrounding the sites and both Neandertals and modern humans could have provisioned there. Also, they suggest the potential existence of a network connecting the Tagus and Ebro valleys, but this is a working hypothesis to be tested with future research. [ABSTRACT FROM AUTHOR]

The Green's function approach (GFA) developed in previous work uses the classical Green's function for point load (Kelvin's fundamental solution, Melan's fundamental solution, and others) and the reciprocity theorem to capture changes in the displacement, strain, and stress fields of a geological formation subjected to the processes of extraction or injection of fluids. The great advantage of this method compared to the classical finite element method (FEM) is that it does not require the imposition of boundary conditions and the problem analysis can be performed considering only the reservoir or other regions of interest. In the original version of the GFA, the displacement field is calculated using an iterative numerical scheme, which decreases the computational performance of the method and may present convergence problems. Such limitations have made it difficult to use the GFA in real problems. The present work proposes a non‐iterative numerical scheme capable of expanding the applicability of GFA and, simultaneously, improving its computational performance. The results presented in this work demonstrate that using this numerical scheme, the GFA consumes up to 17.5 times less CPU time compared to iterative scheme and this relationship can be even greater if the heterogeneity of the material increases. Using a geological profile constructed from seismic images of the Brazilian pre‐salt (Tupi field located in the Santos basin), it is shown that the non‐iterative GFA allows the analysis of complex geological formations. [ABSTRACT FROM AUTHOR]

Thermo‐hydro‐mechanical‐chemical (THMC) interactions are prevalent during CO2 geological sequestration (CGS). In this study, a sequential coupling THMC numerical simulation program was constructed, which can be used to explore the following issues of CGS: fluid and heat flow, solute transport; stresses, displacements and rock failures related to geo‐mechanical effects; equilibrium and kinetic chemical reactions; chemical damage to mechanical properties of the rock. Then, the coupling program was applied to the Ordos CGS Project to study the formation response under the multi‐field interaction caused by CO2 injection. The simulation results show that the mechanical process dominates the short CO2 injection period. Specifically, the formation's permeability near the injection well increases by 43%, due to the reduction of effective stress, which significantly promotes the lateral migration of CO2. When the injection rate exceeds 0.15 million tons per year, the cohesion of the reservoir rock is not enough to resist the shear force inside the rock and rock failure may occur. During the subsequent long‐term sequestration period (200 years), the influence of mineral reactions gradually increases. Due to calcite dissolution, the shear modulus of caprock is predicted to decrease by 7.6%, which will to some extent increase the risk of rock failure. [ABSTRACT FROM AUTHOR]

The storage of fluids in the subsurface is critical for a broad spectrum of applications including managed aquifer recharge, storage of liquefied carbon dioxide and hydrogen, geothermal heat extraction and exploitation of hydrocarbon. It is surprising then, that there has been relatively little measurement of the vertical distribution of poroelastic storage in geologic formations as compared with permeability. We present experiments in which fluid was injected into an important regional aquifer and the depth‐dependent strain response measured using fiber optic distributed acoustic sensing. The formation expansion and contraction in response to fluid injection were several 100 nanostrain. Strain, and the implied storage distribution, was highly localized in specific strata and demonstrated complex, hydromechanical behavior. This new window into fluid‐geomechanical coupling undermines some typically use models and observations currently in practice, but provides potential for complete representation and prediction of fluid storage in the subsurface. Plain Language Summary: A fiber optic cable was used to measure strain in response to water injection and withdrawal in a sandstone aquifer. The strain was found to be focused in limited strata within the aquifer. In some strata, the formation expanded with injection, and in others the formation contracted with injection. This complex behavior is attributed to the interaction between fluid flow and mechanical strain in the porous rock and is contrary to common models of water storage which predict a proportionate expansion of pore space with injection. These results provide important insight into understanding transient flow response to impulse and oscillatory pressure loading of the well. Key Points: Strain and flow direction was correlated or anti‐correlated with injection head, depending on injection intervalInjection and strain behavior was not simply correlated to geophysical or lithologic logsDynamic injection/withdrawal tests are of limited predictive value to managed aquifer recharge [ABSTRACT FROM AUTHOR]

Unconformity‐related uranium (URU) deposits in the Athabasca Basin, Canada, include the highest grade, large tonnage deposits in the world. Recent studies of the Patterson Lake corridor uranium deposits suggest a deep heat source enhances hydrothermal fluid flow and incursion of basinal brines along brittlely reactivated ductile shear zones. However, the spatial extent of the ore systems and lower crustal features capable of driving the hydrothermal cells remained largely unresolved. Three‐dimensional electrical conductivity models derived from inversion of magnetotelluric data and coincident gravity modeling identified a voluminous conductivity anomaly and corresponding gravity low related to a belt of high‐heat producing intrusions that dips below the deposit. Shallow conductive bodies are identified below the deposits and similarly prospective corridors. The volume and location of the intrusive bodies may have provided a source of radiogenic heat that helped drive remobilization of fluids along reactivated structures, redefining the spatial extent of URU systems. Plain Language Summary: The western Athabasca Basin, straddling the border of Saskatchewan and Alberta in Canada, is home to some of the highest‐grade, large tonnage uranium deposits in the world. Recent studies have suggested a spatial connection between uranium ore systems that are found near the earth's surface and geological processes occurring deep within the crust. However, the processes connecting the lower crust to these shallow deposits is poorly understood. This study used 3D models created from magnetotelluric data, a passive a geophysical technique that measures the earth's natural electric and magnetic fields, to image the earth from surface to a depth of 40 km. We identified a voluminous igneous intrusion that extends from the surface to great depths in the earth's crust. We propose that this intrusion may have contributed to the uranium endowment of the basin, and that radiogenic heat from the large igneous body helped circulate uranium‐bearing fluids through the shallow crust along reactivated geologic structures. The modeling, when combined with other geoscientific datasets, showcases the role of high‐heat producing granitic intrusions in driving the hydrothermal fluid cells that formed the deposits. Key Points: Integrated resistivity—gravity modeling over the Arrow uranium deposit in CanadaMagnetotelluric inversion images deep‐seated thermal source and fluid pathways that formed some of the highest‐grade uranium depositsHolistic ore system model illustrates relationship between crustal ore system and lower crustal resistivity anomalies [ABSTRACT FROM AUTHOR]

Summary: Most modern articles in the palaeomagnetism literature are based on statistics developed by Fisher's 1953 paper 'Dispersion on a sphere', which assumes independent and identically distributed (iid) spherical data. However, palaeomagnetic sample designs are usually hierarchical, where specimens are collected within sites and the data are then combined across sites to calculate an overall mean direction for a geological formation. The specimens within sites are typically more similar than specimens between different sites, and so the iid assumptions fail. This article has three principal goals. The first is to review, contrast and compare both the statistics and geophysics literature on the topic of analysis methods for clustered data on spheres. The second is to present a new hierarchical parametric model, which avoids the unrealistic assumption of rotational symmetry in Fisher's 1953 paper 'Dispersion on a sphere' and may be broadly useful in the analysis of many palaeomagnetic datasets. To help develop the model, we use publicly available data as a case study collected from the Golan Heights volcanic plateau. The third goal is to explore different methods for constructing confidence regions for the overall mean direction based on clustered data. Two bootstrap confidence regions that we propose perform well and will be especially useful to geophysics practitioners. [ABSTRACT FROM AUTHOR]

The empirical relationship between the porosity and P‐wave velocity is a useful tool for probing large‐scale underground physical properties and stress states based on P‐wave velocity structures acquired by seismic surveys. In this study, the porosity‐velocity curves were examined using local core sample and logging datasets acquired along the Kumano transect in the Nankai Trough, Southwest Japan. We tested Hashimoto et al.'s (2010) hypothesis that slope apron and accreted sediments have different relationships. Our advantage is using a large amount of logging and core data obtained at multiple sites in the Nankai Trough under various geological conditions, from the incoming oceanic plate to the inner wedge. We identified multiple types of porosity – P‐wave velocity relationships: 1) The first type agrees with the low‐velocity model in the global empirical relation of Erickson and Jarrard 1998), which is observed at lithostatic stress state condition (incoming upper Shikoku basin and slope sediments), 2) The second type consistent with high‐velocity models of the global empirical relation observed at compressive stress state condition (accreted sediments), which have a higher velocity and larger dependence on the porosity than the first type with the same porosity, and 3) The third type for incoming sediments with high smectite content has lower velocity than the first type. Based on our results, the transition between the first and second porosity – velocity relationships occurs in the prism toe, implying that compressive stress due to subduction controls acoustic properties and the lithification process of these sediments. Plain Language Summary: Physical properties of rocks in subduction zones are important factors controlling genesis of earthquakes. Among many kinds of physical properties, this study focuses on the relationship between porosity and P‐wave velocity at the Nankai Trough, Southwest Japan. As this relationship is affected by how the soft sediments are lithified through the subduction process, it has been studied frequently to understand physical properties and stress states of geological formations around plate boundary faults. This study compiles P‐wave velocity datasets acquired by scientific drilling projects in offshore regions, as well as porosity datasets. We tested the hypothesis proposed by a previous study that there are two types of the relationships between the two quantities. We find these two types are consistent with the global empirical relationships observed at lithostatic and compressive stress states respectively. The former includes sediments on the oceanic plate before subduction and slope apron sediments. The latter are sediments accreted toward the Japan arc. We also find that the transition from the former to the latter occurs in the sediments at the tip of accretionary prism. This suggests that compressive stress state due to subduction plays an important role in controlling the acoustic properties of sediments. Key Points: Porosity and P‐wave velocity data were compiled to investigate their relationships at the Kumano transect in the Nankai TroughAccreted sediments have higher P‐wave velocity compared with incoming and slope apron sediments with the same porosityThe stress state in the accretionary prism might be a factor controlling the porosity – P‐wave velocity relationships of sediments [ABSTRACT FROM AUTHOR]

Granular materials often present correlations between particle size and shape due to their geological formation and mechanisms of weathering and fragmentation. It is known that particle shape strongly affects shear strength. However, the effects of shape can be modified by the role the particle plays in a sample given its size. We explore the steady shear strength of samples composed of particles presenting size‐shape correlations and we focus on the case of particle elongation in two opposite scenarios: (A) large elongated grains with finer circular grains and (B) large circular grains with elongated finer grains. By means of numerical simulations, we probe the shear strength of samples of varying particle size span from mono to highly polydisperse and particle aspect ratios varying between 1 and 5. We find that the two correlations tested strongly impact the shear strength as particle size span evolves. Microstructural analyzes allow us to identify how each correlation affects connectivity and anisotropies linked to the orientation of the particles and load transmission. Decompositions of the stress tensor let us identify the sources of the different mechanical behavior in each correlation and determine the contributions of each particle shape to macroscopic shear strength. This study proves that common small‐scaling methods based on truncated or parallel particle size distributions can incur in under/over‐estimations of shear strength if particle shapes are not considered in the scaling process. [ABSTRACT FROM AUTHOR]

The breakup of Pangea fundamentally shaped modern continents and controlled the climatic distribution and biodiversity on Earth. Although our knowledge on the processes that control the assembly and breakup of supercontinents has significantly improved, the timing of supercontinent assembly and breakup initiation remains in some cases controversial. According to the available data, the assembly of Pangea was completed in middle Permian time, resulting in the formation of major orogenic belts and transform faults like the N–S‐trending, dextral, Caltepec fault in Mexico. Pangea breakup initiation is bracketed to early Middle Triassic time. In this work, we present new sedimentological, structural and U‐Pb geochronological data from a fluvial unit, the Matzitzi Formation of southern Mexico, the age and tectonic setting of which have remained an enigma for the past century. Our data document that the Matzitzi Formation is the stratigraphic record of a late Permian, anastomosing fluvial system that flowed in a—NNE‐trending extensional trough developed on top of the Caltepense belt, a transpressive belt formed along the Caltepec fault. We propose and discuss three possible scenarios for the tectonic setting of the Matzitzi Formation. In the first scenario, the unit is the stratigraphic record of the Caltepec fault late activity, which caused local NW–SE extension along the western margin of Pangea during its final assembly. In the second scenario, the Matzitzi Formation was deposited in an extensional basin formed by slab rollback along the western equatorial Pangea margin. In the third scenario, the extensional basin of the Matzitzi Formation was formed in the framework of the Pangea breakup. In this case, our data would suggest that Pangea breakup initiation must be dated back to late Permian time, which is ca. 15 m.y. older than the Middle Triassic age documented by the previous work. Considering that evidence of Permian extension has also been reported along the Appalachian belt, we suggest that the Matzitzi Formation was deposited during regional‐scale extension of western equatorial Pangea; therefore, we preliminarily support the third scenario. The distribution of Permian extension along suture belts developed during Pangea assembly highlights the fundamental role played by pre‐existent zones of weakness in the breakup of a supercontinent. [ABSTRACT FROM AUTHOR]

The expansion of agricultural frontiers has increased the use of sandy soils as cropping areas; however, the water‐retention capacity (WRC) of the soil is a crucial factor. Thus, fast and accurate methodologies, such as spectroscopy, have gained importance to identify physical‐hydric and other attributes related to the WRC. Some theories indicate the micromorphometry of particles is an important factor in sandy soils. This study (I) investigated the WRC of sandy soils from distinct geologic formations and the influence of particle micromorphometry on the WRC; (II) evaluated the sensitivity of Vis–NIR and MIR spectra to characterise physical‐hydric attributes and particle micromorphometry; and (III) quantified physical‐hydric attributes of sandy soils from their physical attributes, particle micromorphometric indices, and the visible‐near infrared‐mid infrared (Vis–NIR‐MIR) spectra. We determined the values of field capacity (FC), permanent wilting point (PWP), available water (AW), clay, sand, silt, sand fractions, and OM as well as the micromorphometric indices and Vis–NIR and MIR reflectance of 29 sandy soil profiles. Soil attributes were correlated with each other and with the Vis–NIR and MIR spectra to understand their relationship with the WRC. The correlation and the principal component analyses (PCA) were performed to understand the relationship between Vis–NIR and MIR spectra and sand grain micromorphometry. Mathematical models were developed to estimate FC, PWP, and AW using soil attributes, micromorphometry, Vis–NIR, and MIR as predictor variables. Roughness of sand particle greatly influenced the WRC of sandy soils. The MIR region showed high sensitivity to identify different WRC patterns and particle micromorphometry in sandy soils. The Vis–NIR and MIR spectra presented high accuracy to predict FC and PWP of sandy soils. The mathematical models that used soil attributes + micromorphometry presented excellent calibration parameters; however, they did not show accuracy in the validation set. Highlights: The influence of particle roughness on water retention of sandy soils was proven.Roughness had a greater influence on water retention than texture proportions for highly sandy soils.MIR spectra correlate strongly with the roughness of the very fine sand fraction.MIR spectra and roughness can estimate sandy soils water retention with high accuracy. [ABSTRACT FROM AUTHOR]

The oil industry uses Portland cement in their wells, which is manufactured predominantly in accordance with American Petroleum Institute classifications. Also, cements following standards applied in civil/construction engineering are used, which gain importance recently. A field case is reviewed where a cement plug job was performed across the Zechstein formation of a well in a Rotliegend Group and chemical interactions between the cement slurry and a geological formation could be observed. Furthermore, examples for methods to characterize the porosity of the dry cement powder are referenced. [ABSTRACT FROM AUTHOR]

The Lower Carboniferous sediments at Wadi Abu El Mogheirat consist of four stratigraphic formations, from base upwards: Um Bogma, El Hashash, Magharet El Maiah and Abu Zarab formations. The most‐concentrated radioactive anomalies at Wadi Abu El Mogheirat are in the middle member of the Um Bogma Formation. The gibbsitic marl in this formation shows the highest uranium contents (around 710 ppm). Gibbsitic marl and black gibbsite of the middle Um Bogma Formation show higher enrichment in Co, Cu, Mn, Ni, Pb, Zn, U, V, Ce and Th. Black gibbsite contains the highest total rare earth elements concentration, especially in terms of LREEs, while gibbsitic marl contains the highest content of HREEs. Anomalous contents of gold at Wadi Abu El Mogheirat are recorded for the first time in the gibbsitic marl (content: 10.4 ppm), black gibbsite (2.8 ppm) of the middle member of the Um Bogma Formation and in the siltstones of the El Hashash Formation (0.6 ppm). Gibbsitic marl shows the presence of uranothorite, celestite, zircon, atacamite, barite, xenotime and rutile. These characteristic demonstrate that the middle member of the Um Bogma Formation constitutes a potential source for gold. This conclusion is reinforced by the potential to exploit other metals such as Co, Cu, Mn, Ni, Pb, Zn, U, V, Th and Ce as by‐products. [ABSTRACT FROM AUTHOR]

Induced earthquakes caused by hydraulic fracturing are a growing concern, with risks that are often managed by traffic light protocols (TLPs). Here, we apply a risk‐informed strategy for choosing TLP red‐light thresholds. We utilize a combination of probabilistic maximum magnitudes, formation depth, site amplification, ground motion relationships, felt/damaging shaking tolerances, and population information to simulate the spatial distribution of nuisance and damage impacts. We apply this approach to many of the prominent North American shale plays that have caused earthquakes: the Horn River Basin, the Duvernay Formation, the Montney Formation, the Utica Shale, the Marcellus Shale, the SCOOP & STACK play in Oklahoma, the Eagle Ford Formation, and the Delaware Basin. We find that induced earthquake impacts are spatially heterogeneous, depending most strongly on population density. These spatial heterogeneities vary on different length scales, depending on if they are related to nuisance (longer range, 100s kms) or damage (shorter range, 10s kms). Because of this variability, we suggest an approach that sets red‐light magnitudes based on tolerances to nuisance and damage risks (varying between Mw 2.0–5.0). Comparison of the results between North American shale plays where TLPs have been enacted suggests that nuisance risks have been an influencing factor in determining red‐light thresholds. Our method provides quantitative guidelines for traffic light protocols designed in a risk‐informed manner that retains the implementational simplicity of magnitude‐based thresholds. In addition, our results provide a benchmark for jurisdictional nuisance tolerances that future TLPs could be guided by. Plain Language Summary: Subsurface injection operations, like hydraulic fracturing, have the potential to cause earthquakes. Typically, the risks of these earthquakes are managed through a traffic light protocol (TLP): a system that prescribes an operational stopping point (red‐light) for injection operations. We have devised a method to inform the choice of the red‐light threshold quantitatively in a risk‐informed manner, by considering nuisance and damage potential from earthquake ground shaking that could occur after well shut‐in. We apply this approach to the major shale plays of North America that have caused earthquakes. These risks are spatially heterogenous, so choosing a single earthquake magnitude for a red‐light would not be fair. A fairer approach would be to choose tolerances for nuisance and damage and then set the (spatially varying) magnitude such that these tolerances are not exceeded. We compare our results within shale plays, but also at a continental play‐by‐play scale. Generally, the red‐light thresholds adopted by jurisdictions reflects these differences (justifying a risk‐based approach). Examination of these differences in risk tolerances suggests consistencies within plays that could be used as guidelines for future TLPs. Overall, our method provides a means to determine red‐light thresholds, depending on a jurisdiction's tolerance to earthquake risks. Key Points: We apply a risk‐informed method for choosing induced earthquake red‐light thresholds to shale plays in North AmericaNuisance and damage risks are spatially heterogeneous both between and within the considered shale playsRed‐light magnitude thresholds based on these risks vary spatially (Mw 2.0–5.0), which argues against the use of a single threshold [ABSTRACT FROM AUTHOR]

The electrical resistivity‐porosity relationship of porous media is critical for reliable formation evaluation. Archie's equation is empirical, and uses only porosity as pore‐space property, neglecting the spatial variability of the pore space; its fitting parameters may have unclear physical meaning and be nonconstant over a wider porosity range or in spatially complex rocks. We use microfluidics augmented with pore‐network modeling to investigate the effects of pore‐space properties and their evolution processes on electrical resistivity‐porosity relationships. Both a flow‐pattern parameter and a measure of porosity efficiency are implemented to quantify the spatial variability of the flow field and the conduction efficiency of porous media. Results indicate that both pore‐size distribution and pore‐space evolution impact the electrical behavior considerably. In cases of unimodal pore‐size distributions, a larger pore‐size variation or a higher porosity reduction in small pores results in higher values of Archie's porosity exponent, m; the flow pattern becomes more heterogeneous, and the efficiency of porosity to conduct electricity decreases. For cases of bimodal pore‐size distributions, the formation factor‐porosity relationship is nonlinear in log–log plots; the flow behavior is primarily affected by the fraction and connectivity of large pores. Results suggest that using porosity alone as pore‐space characteristic is inadequate to describe the electrical behavior of complex porous media. Petrophysical classification based on flow patterns and porosity efficiency is an effective alternative to differentiate the results. We introduce the electrical quality index as an effective parameter for petrophysical classification, which is verified with core data for both Fontainebleau sandstones and carbonates. Plain Language Summary: The electrical current conducts mainly through the pore fluid in a saturated porous medium. The formation factor—ratio of the electrical resistivity of saturated porous media to the electrical resistivity of the pore fluid—contains information of the pore space in subsurface rocks valuable for petroleum engineers and earth scientists. The widely used Archie's equation relates porosity and formation factor. However, Archie's equation is empirical, uses only porosity to represent a complex pore space, and ignores how the electrical current travels in the pore space. We study effects of pore‐space properties on electrical resistivity in porous media using well‐designed pore space characterized by statistical pore‐size distributions. The electrical resistivity of the pore space is measured experimentally in micromodels—a pore space fabricated on glass chips, and simulated in pore networks—a virtual lattice of pores. Results show that the electrical flow field is heterogeneous even at pore scale, and both pore‐size distribution and diagenetic processes impact the electrical behavior considerably. We propose parameters to quantify the spatial variability of the flow field and the conduction efficiency of the pore space. These parameters provide additional information of the quality of the pore space in conducting flow and can be used in petrophysical rock classifications. Key Points: Effects of pore geometry and its evolution on electrical resistivity is investigated by microfluidic experiments and pore‐network modelingThe use of porosity alone as pore‐space property in Archie's equation is inadequate to describe the electrical behavior in porous mediaParameters are introduced to quantify the flow heterogeneity and conduction efficiency in the pore space and for electrical rock typing [ABSTRACT FROM AUTHOR]

Fluid flow through geological formations is often concentrated on distinct preferential flow paths owing to the presence of fractures or large‐scale permeability structures. However, the existence of such structures is not a mandatory condition of preferential paths formation. Pore‐scale spatial fluctuations of pore size and/or pore connectivity in statistically stationary porous media, if sufficiently large, can also lead to the concentration of fluid flow on distinct pathways. In this paper, we attempted to establish the conditions of formation of preferential flow paths in heterogeneous porous media in terms of pore‐size heterogeneity and pore connectivity. We simulated steady‐state flow through stochastically constructed two‐ and three‐dimensional pore networks, in which the width of the pore radius distribution and the pore coordination number (a measure of pore connectivity) were varied. We developed new techniques based on graph theory to identify potential preferential flow paths and characterize them. We observed a gradual transition from approximately uniform flow fields in low heterogeneity/high connectivity networks to flow localization on preferential paths with increasing pore‐size heterogeneity and decreasing connectivity. The transition occurred at lower heterogeneity levels in three‐dimensional than in two‐dimensional simulations and was less influenced by pore connectivity variations. These results were summarized in a phase diagram in pore‐size heterogeneity/pore connectivity parameter space, which we found consistent with relevant real rocks data. Plain Language Summary: In general, fluid flow underground is unevenly distributed. Most of the flow occurs in distinct channels called preferential flow paths, which are often associated with large‐scale structures such as highly permeable layers or fractures. Preferential flow paths can also form in rock formations in which such features are absent. The only requirements are a sufficiently high level of pore size heterogeneity and/or partial disconnection of the pore space. In this study, we simulated fluid flow through heterogeneous and partially connected pore networks and used graph theory to identify and characterize the possibly existing preferential flow paths, that formed owing to the randomness of the pore space. We were thus able to establish a phase diagram showing the regions in heterogeneity/connectivity parameter space where fluid flow is evenly distributed and where it is concentrated on preferential flow paths. These two regions are separated by a broad transition zone where the flow morphology is intermediate between the two extremes. By comparing our results to those of previously published studies, we found that the phase diagram appeared consistent with real rocks data. Key Points: A gradual transition from approximately uniform flow field to flow localization on preferential paths was observedThe graph‐theoretical algorithm was applied to identify and characterize the potential preferential flow pathsA phase diagram was constructed for quantifying the transition from uniform flow field to flow concentration in pore networks and real rocks [ABSTRACT FROM AUTHOR]

Focused fluid flow shapes the evolution of marine sedimentary basins by transferring fluids and pressure across geological formations. Vertical fluid conduits may form where localized overpressure breaches a cap rock (permeability barrier) and thereby transports overpressured fluids towards shallower reservoirs or the surface. Field outcrops of an Eocene fluid flow system at Pobiti Kamani and Beloslav Quarry (ca 15 km west of Varna, Bulgaria) reveal large carbonate‐cemented conduits, which formed in highly permeable, unconsolidated, marine sands of the northern Tethys Margin. An uncrewed aerial vehicle with an RGB sensor camera produces ortho‐rectified image mosaics, digital elevation models and point clouds of the two kilometre‐scale outcrop areas. Based on these data, geological field observations and petrological analysis of rock/core samples, fractures and vertical fluid conduits were mapped and analyzed with centimetre accuracy. The results show that both outcrops comprise several hundred carbonate‐cemented fluid conduits (pipes), oriented perpendicular to bedding, and at least seven bedding‐parallel calcite cemented interbeds which differ from the hosting sand formation only by their increased amount of cementation. The observations show that carbonate precipitation likely initiated around areas of focused fluid flow, where methane entered the formation from the underlying fractured subsurface. These first carbonates formed the outer walls of the pipes and continued to grow inward, leading to self‐sustaining and self‐reinforcing focused fluid flow. The results, supported by literature‐based carbon and oxygen isotope analyses of the carbonates, indicate that ambient seawater and advected fresh/brackish water were involved in the carbonate precipitation by microbial methane oxidation. Similar structures may also form in modern settings where focused fluid flow advects fluids into overlying sand‐dominated formations, which has wide implications for the understanding of how focusing of fluids works in sedimentary basins with broad consequences for the migration of water, oil and gas. [ABSTRACT FROM AUTHOR]

Estimating the longitudinal dispersion coefficient DL in flow through heterogeneous porous media is paramount to many problems in geological formations. Moreover, although it is well‐known that DL is sensitive to the morphology of such formations, it has been very difficult to establish a firm link between the two. We describe a novel deep convolutional neural network (DCNN) for estimating DL. The inputs for training of the network are a large and diverse set of data consisting of three‐dimensional images of porous media, as well as their porosity, and the associated DL values computed by random‐walk particle‐tracking (RWPT) simulations. The trained network predicts DL very rapidly, and its predictions are in excellent agreement with the data not used in the training. Thus, a combination of the DCNN and RWPT simulation provides a powerful tool for studying many flow‐related phenomena in geological formations, and estimating their properties. Plain Language Summary: Measuring or computing the dispersion coefficient DL in flow through porous media, a fundamental characteristic of transport in geological formations and risk analysis, is a time‐consuming endeaver. Moreover, although DL is sensitive to the morphology of a pore space, a direct link between the two has been missing. We proposed a deep convolutional neural network for predicting DL, using 3D images of porous media and their porosities. The accuracy of the predictions for the actual data indicates that the ability of the network for estimating the important flow and transport properties of porous media for new input data. The present work was at the core scale, on the order of the physical sizes of the sandstones used in our study. The same approach may be used at the eld scale. In that case, one generates the input data by following the same procedure, except that the data should be generated for models in which the permeability and porosity of the formation vary spatially, and represent correlated fields. Work in this direction is in progress. Key Points: Dispersion coefficientConvolutional neural networkFlow through porous media [ABSTRACT FROM AUTHOR]

This paper makes a call for an urban political ecology (UPE) which engages more extensively with Earth's geological formations. As a material at the centre of global urbanisation process, sand is offered as a geological entry point. The paper presents an analysis of the urbanisation of sand, or the ways in which sand is brought into the urban realm, grounding this reading in Accra—a growing city on Ghana's Atlantic coast. Drawing from 14 months of ethnographic fieldwork, the paper charts the socio‐natural politics through which sand is first unearthed from the edges of the city—an extractive processes otherwise known as "sand winning" in Ghana. By examining the forms of power which govern uneven revenue flows to communities, the displacement of farming groups, the widespread loss of farmland and a contested regime of governance, the analysis exposes the socio‐natural politics through which the city's geological baseline is first unearthed. [ABSTRACT FROM AUTHOR]

Objectives: The Willwood Formation of the southern Bighorn Basin, Wyoming is a fluvial rock sequence that spans approximately 3 million years of early Eocene time. It has yielded one the largest collections of fossil mammals in the world including thousands of dentitions of extinct lemur‐like primates known as notharctines. In the southern Bighorn Basin, specimens of these primates have been collected on numerous paleontological expeditions and the stratigraphic levels yielding the dentitions have been carefully recorded. Notharctine dentitions represent a rare opportunity to study morphological variation in a single anatomical system through time among closely related individuals. Materials and Methods: Prior studies of Bighorn Basin notharctines through time produced measurements of hundreds of specimens but I report here results from measurement and comparison of the dentitions and dentaries of more than 3,000 specimens, all stratigraphically mapped. Results: Variation in premolar and molar area and variation in dentary depth are apparent throughout the section. Specimens with relatively small teeth and dentaries are known from the older part of the section. In younger rocks, variation in tooth area among specimens increases. Variation in tooth area is continuous and overlaps extensively both within and between stratigraphic levels. Other dental variables examined by inspection change in a mosaic and continuous fashion through the section. These features include variation in the presence and number of paraconids on the lower fourth premolar (p4), the size and shape of the entoconid notch on the lower first and second molars, and the relative development of the pseudohypocone, mesostyle, and cingula on the upper molars. Discussion: These broad patterns can be identified despite notharctine alpha taxonomy being in need of extensive revision and, importantly, simplification. Such revision is beyond the scope of this article but is essential if we are to develop a taxonomy that is both free of stratigraphic influence and useful for rapid, repeatable species assignment. Boundaries among the patterns of tokogenesis, anagenesis, and cladogenesis are blurred in this dense sample of extinct primates. While pattern of evolution, a population‐level phenomenon, may be difficult to falsify in the fossil record, this notharctine sample suggests that in the rare instance such as this, when the fossil record is densely sampled, change through time is continuous and more consistent with gradual evolution. [ABSTRACT FROM AUTHOR]

The Yunkai low uplift with low exploration degree is close to the Baiyun sag, and has hydrocarbon exploration potential in the deepwater area of the Pearl River Mouth Basin. Based on seismic and drilling data, balanced profiles and growth strata, this paper mainly discusses geological structures and formation processes of the Yunkai low uplift, and also analyzes the characteristics of fault system and their influence on hydrocarbon migration and accumulation. The EW‐trending basement faults divide the Yunkai low uplift into two parts, i.e. the southern sector and the northern sector. The northern sector is a relatively wide and gentle uplift, while the southern sector is composed of two secondary half‐grabens with faulting in the south and overlapping in the north. The Yunkai low uplift experienced three major formation stages, including the rapid uplifting stage during the deposition period of the Eocene Wenchang Formation, the slow uplifting stage during the deposition period of the Late Eocene‐Middle Miocene Enping‐Hanjiang formations, and the whole burial stage from the Middle Miocene to present. The extensional faults in the Yunkai low uplift and its adjacent areas strike mainly along the NW, NWW and near‐EW directions. Also, the strikes of faults present a clockwise rotation from the deep to the shallow strata. According to effects of faults on hydrocarbon accumulation, the faults in the Yunkai low uplift and its adjacent areas can be divided into trap‐controlled faults and source‐controlled faults. The trap‐controlled faults control trap development and can effectively seal oil and gas. The source‐controlled faults connect directly source rocks and reservoirs, which are highly active during the rifting stage and weakly active since the Miocene. This activity features of the source‐controlled faults is beneficial to migration of the early crude oil from the Baiyun sag to the high part of the Yunkai low uplift, but is not good for migration of the late natural gas. In the Yunkai low uplift and its adjacent areas, the traps in the deep Zhuhai and Enping formations that are close to source rocks in the Baiyun sag should be the favorable exploration objectives. [ABSTRACT FROM AUTHOR]

In 2011, the German Bundestag decided to phase out nuclear energy. The resulting waste will remain highly radioactive for many hundreds of thousands of years and represents a considerable danger for future generations. This radioactive waste is to be safely disposed of in deep geological formations (e. g. salt, clay or crystalline). The repositories will be sealed by means of engineered barrier systems. The impermeability of these structures is indispensable. In the current research phase, various materials are being investigated and methods for monitoring the structures are being developed. In this context, the investigation of cracks is a priority topic. In recent years, extensive experience in the investigation of in‐situ test objects in full scale were gained. The measurements were performed in the Morsleben repository for radioactive waste at the test structure for the in‐situ experiment "Sealing structure in rock salt" and in the Teutschenthal mine at the large‐scale GV2 test structure. With a newly developed ultrasonic measuring system it has been possible to achieve penetration depths of up to approx. 9.0 m. Measurements with the Large Aperture Ultrasonic System in combination with the Synthetic Aperture Focusing Technique reconstruction method show that the non‐destructive testing of sealing structures is possible and the use of the measuring system for quality assurance in the construction of sealing structures is promising. [ABSTRACT FROM AUTHOR]

The Palaeocene–Eocene boundary (PEB) interval has been recognized in the Patala Formation, Nammal Gorge Section, Pakistan using lithostratigraphy, stable carbon isotope stratigraphy and integrated biostratigraphy. Four distinct lithological units are identified in the Patala Formation in stratigraphic order from bottom to top; unit‐1 to unit‐4. The top of unit‐3 hosts three closely spaced unconformities demarcated as U1, U2, and U3. The PEB interval is represented by a negative shift of 1.61‰ in δ13CV‐PDB representing the carbon isotopic excursion (CIE) in unit‐2. Based on the encountered foraminifera, dinocysts, and calcareous nannoplanktons, the following biozones are identified across the PEB; two larger benthonic foraminiferal (LBF) zones (SBZ4 and SBZ5), the zonal boundary slightly postdating the CIE, two smaller benthonic foraminiferal zones (BB1 and BB2), three planktonic foraminiferal zones (P4/P5 + E1), four dinocysts zones (Pak‐DV, Pak‐DVI, Pak‐DVII, Pak‐DVIII), and two calcareous nannoplankton subzones (NP9a and NP9b). The following protist, dinocyst and calcareous nannoplanktons encountered in the studied interval advocates for the placement of the possible PEB at the level between samples NAM‐SH‐07 and 08; 1—presence of the smaller benthonic foraminifera Angulogavelinella avnimelechi diagnostic of the base of the CIE and the benthonic extinction event (BEE) Tethys wide, 2—presence of the cosmopolitan and the PEB diagnostic dinocyst species 'Axiodinium augustum', 3—presence of the PEB diagnostic Rhomboaster‐Discoaster calcareous nannoplankton assemblage. The LBF species Alveolina vredenburgi [a marker species of the Larger Foraminiferal Turnover (LFT) associated with the Palaeocene Eocene Thermal Maximum (PETM) and PEB in western Tethys] occurs slightly above the onset of the CIE. Previously reported compositional change in the LBF assemblage from the Salt Range [i.e. the replacement of the Palaeocene orbitoidiform LBF (Setia and Orbitosiphon) by the Eocene LBF (Orthophragminids, Alveolina, Nummulites and Assilina)] also postdates the PEB interval here. The late appearance of Alveolina vredenburgi and the compositional change in the LBF after the onset of the CIE are attributed to the facies variation across the PEB reflecting fluctuating depositional environment due to the active tectonic across this interval. This fluctuation is evident from the smaller benthonic and planktonic foraminiferal dominating assemblages in unit‐2 representing bathyal settings followed by LBF dominating unit‐3 representing shallow carbonate platform settings. The change in LBF assemblage closely resembles the well‐known LFT associated with the PETM as well as the carbonate platform stage III and the PEB reported from other Tethyan sections. [ABSTRACT FROM AUTHOR]

This study demonstrates the use of ASTER data for the mapping of gypsum deposits and associated geological formations that occurred in the Thumrait region of southern Oman. The measurement of spectra over samples of gypsum in the 1,300–2,500 nm wavelength using a PIMA spectrometer showed the presence of distinct absorptions at 1400–1600, 1750, 1940, 2,100, and 2,400 nm characteristics to OH stretching, H2O combinations, and SO bending overtones and stretching, respectively. Studying the unique spectral absorption characters of gypsum samples, we developed a false color composite (FCC) and an image by decorrelation stretch using the spectral bands 7, 3, and 2 of ASTER. The results FCC showed the regions of gypsum occurrences, and the decorrelated image discriminated the gypsum occurrences from other geological formations of the area. The study of surface mineralogy of the region using the VNIR‐SWIR bands by the spectral angle mapper method showed the presence of sulfate, carbonate, and clay minerals of the geological formations in the study area. We compared the results of ASTER with the results obtained using spectral bands 12, 8, and 4 of Sentinel‐2A processed by the same methods. The study showed that the spectral bands of ASTER can be used for mapping the gypsum and associated geological formations. [ABSTRACT FROM AUTHOR]

Geologic carbon storage is required for achieving negative CO2 emissions to deal with the climate crisis. The classical concept of CO2 storage consists in injecting CO2 in geological formations at depths greater than 800 m, where CO2 becomes a dense fluid, minimizing storage volume. Yet CO2 has a density lower than the resident brine and tends to float, challenging the widespread deployment of geologic carbon storage. Here, we propose for the first time to store CO2 in supercritical reservoirs to reduce the buoyancy‐driven leakage risk. Supercritical reservoirs are found at drilling‐reachable depth in volcanic areas, where high pressure (p > 21.8 MPa) and temperature (T > 374°C) imply CO2 is denser than water. We estimate that a CO2 storage capacity in the range of 50–500 Mt yr−1 could be achieved for every 100 injection wells. Carbon storage in supercritical reservoirs is an appealing alternative to the traditional approach. Plain Language Summary: Geologic carbon storage, which consists in returning carbon deep underground, should be part of the solution to effectively reach carbon neutrality by the middle of the century to mitigate climate change. CO2 has been traditionally proposed to be stored in sedimentary rock at depths below 800 m, where CO2 becomes a dense fluid, minimizing the required storage volume. Nevertheless, CO2 is lighter than brine in the traditional concept, so a rock with sufficient sealing capacity should be present above the storage formation to prevent leakage. Indeed, one of the main hurdles to deploy geologic carbon storage is the risk of CO2 leakage. To reduce this risk, we propose a novel storage concept that consists in injecting CO2 in reservoirs where the pore water stays in supercritical conditions (pressure and temperature higher than 21.8 MPa and 374°C, respectively) because at these conditions, CO2 becomes denser than water. Consequently, CO2 sinks, leading to a safe long‐term storage. This concept, which could store a significant portion of the total requirements to decarbonize the economy, should start being implemented in deep volcanic areas, given that supercritical reservoirs are found at relatively shallow depths between 3 and 5 km. Key Points: We propose a novel geologic carbon storage concept that reduces the buoyancy‐driven CO2 leakage riskBy injecting CO2 in reservoirs where the resident water stays in supercritical conditions, CO2 sinks because it is denser than pore waterSupercritical reservoirs are found at relatively shallow depths between 3 and 5 km in deep volcanic areas [ABSTRACT FROM AUTHOR]

Despite the abundance of shales in the Earth's crust and their industrial and environmental importance, their microscale physical properties are poorly understood, owing to the presence of many structurally related mineral phases and a porous network structure spanning several length scales. Here, the use of coherent X‐ray diffraction imaging (CXDI) to study the internal structure of microscopic shale fragments is demonstrated. Simultaneous wide‐angle X‐ray diffraction (WAXD) measurement facilitated the study of the mineralogy of the shale microparticles. It was possible to identify pyrite nanocrystals as inclusions in the quartz–clay matrix and the volume of closed unconnected pores was estimated. The combined CXDI–WAXD analysis enabled the establishment of a correlation between sample morphology and crystallite shape and size. The results highlight the potential of the combined CXDI–WAXD approach as an upcoming imaging modality for 3D nanoscale studies of shales and other geological formations via serial measurements of microscopic fragments. [ABSTRACT FROM AUTHOR]

Studying lithic raw material sourcing, processing and distribution is helpful when trying to reconstruct the territory, ecology, and cultural practices of Neanderthal groups. The use of multiple methods in such analyses allows for more refined characterizations to be made, helping to distinguish between materials better than any single method. Although 85% of the raw materials making up the Mousterian assemblage at the Navalmaíllo Rock Shelter (Pinilla del Valle, Madrid Region of Spain) correspond to the available local geological resources, 10% is made of white/beige chert, which is not registered in regional geological cartography. Petrographic and scanning electron microscopy with energy dispersive X‐ray spectroscopy analyses were performed to determine the origin of this white/beige chert and thus shed light on the procurement strategies of the Neanderthal groups that occupied the rock shelter. The results show this chert to correspond to three different types of rock: quartz–kaolinite rocks from dykes, cretaceous marine cherts, and quartz fillings of cavities/fractures. These findings are in accordance with the geological features and formations present in the Lozoya valley, as recorded during a geoarchaeological survey, and indicate that the Neanderthals occupying the center of the Iberian Peninsula possessed a detailed knowledge of the landscape that allowed them to exploit its resources during MIS5a–early MIS4. [ABSTRACT FROM AUTHOR]

Understanding the causes of the Sino‐Japanese disjunctions in plant taxa has been a central question in eastern Asian biogeography, with vicariance or long‐distance dispersal often invoked to explain such patterns. Diabelia Landrein (Caprifoliaceae; Linnaeoideae) comprises four shrubby species with a Sino‐Japanese disjunct distribution. The species diversification time within Diabelia, covering a long geological history of the formation process of the Sino‐Japanese flora, dated back to the middle Oligocene, therefore, Diabelia would be an ideal model to elucidate the biogeographic patterns of Sino‐Japanese disjunctions with climate fluctuation. In this study, we analyzed complete plastome sequence data for 28 individuals representing all four species of Diabelia. These 28 plastomes were found to be highly similar in overall size (156 243–157 578 bp), structure, gene order, and content. Our phylogenomic analysis of the plastomes supported a close relationship between Diabelia ionostachya (Nakai) Landrein & R.L. Barrett var. wenzhouensis (S.L. Zhou ex Landrein) Landrein from eastern China and Diabelia spathulata (Siebold & Zucc.) Landrein var. spathulata from Japan. Diabelia serrata (Siebold & Zucc.) Landrein was identified as sister to a population of Diabelia sanguinea (Makino) Landrein from Tochigi in central Japan and D. spathulata Landrein, from Toyama, central Japan. Most Diabelia lineages were estimated to have differentiated 8–28 Mya. Our results indicate that two independent vicariance events could explain the disjunction between Japan and Korea in the mid to late Miocene, and between Zhejiang and Japan in the early Miocene. [ABSTRACT FROM AUTHOR]

To reach the reduced carbon emission targets proposed by the Paris agreement, one of the widely proposed decarbonizing strategies, referred to as negative emissions technologies (NETs), is the production and combustion of bioenergy crops in conjunction with carbon capture and storage (BECCS). However, concerns have been increasingly raised that relying on the potential of BECCS to achieve negative emissions could result in delayed reductions in gross CO2 emissions, with consequent high risk of overshooting global temperature targets. We focus on two particular issues: the carbon efficiency and payback time of bioenergy use in BECCS and the potential constraints on the supply of bioenergy. The simplistic vision of BECCS is that 1 tonne of CO2 captured in the growth of biomass equates to 1 tonne of CO2 sequestered geologically, but this cannot be the case as CO2 is emitted by variable amounts during the lifecycle from crop establishment to sequestration below ground in geological formations. The deployment of BECCS is ultimately reliant on the availability of sufficient, sustainably sourced, biomass. The two most important factors determining this supply are land availability and land productivity. The upper bounds of the area estimates required correspond to more than the world's harvested land for cereal production. To achieve these estimates of biomass availability requires the rapid evolution of a multitude of technological, social, political and economic factors. Here, we question whether, because of the limited sustainable supply of biomass, BECCS should continue to be considered the dominant NET in IPCC and other scenarios achieving the Paris targets, or should it be deemed no longer fit for purpose? [ABSTRACT FROM AUTHOR]

The rate of carbon dioxide (CO2) dissolution in saline aquifers is the least well‐constrained of the secondary trapping mechanisms enhancing the long‐term security of geological carbon storage. CO2 injected into a heterogeneous saline reservoir will preferentially travel along high permeability layers increasing the CO2‐water interfacial area which increases dissolution rates. We provide a conservative, first‐principles analysis of the quantity of CO2 dissolved and the rate at which free‐phase CO2 propagates in layered reservoirs. At early times, advection dominates the propagation of CO2. This transitions to diffusion dominated propagation as the interfacial area increases and diffusive loss slows propagation. As surrounding water‐filled layers become CO2 saturated, propagation becomes advection dominated. For reservoirs with finely bedded strata, ∼10% of the injected CO2 can dissolve in a year. The maximum fraction of CO2 that dissolves is determined by the volumetric ratio of water in low permeability layers and CO2 in high permeability layers. Plain Language Summary: To limit global warming to 2°C, it is likely that large amounts of carbon dioxide (CO2) will need to be stored underground. A significant fraction of the total possible storage space for CO2 is in salt water reservoirs, kilometers beneath the surface. It is important that once the CO2 has been injected underground, it is securely trapped, otherwise, there is a risk that it could leak back to the surface. After the CO2 is injected into these reservoirs, it can dissolve in the surrounding water, greatly reducing the risk of leakage, although complete dissolution of all the injected CO2 may take millions of years. However, preferential flow of CO2 along more permeable layers in geological formations creates a complex front between the water and CO2 which increases the surface area available for dissolution. This study calculates the minimum amount of injected CO2 that can dissolve in such a reservoir and how far it travels. Using injection of CO2 for enhanced oil recovery at the Salt Creek Field in Wyoming as an example, we find that in one year around 10% of the total injected CO2 can dissolve into the surrounding water by this process and become trapped. Key Points: Injection of carbon dioxide into finely bedded reservoirs leads to enhanced contact area with water and hence enhanced dissolution ratesPropagation rates of free‐phase carbon dioxide transition from advection to diffusion dominated as the contact area with water increasesFor injection into the Salt Creek reservoir, Wyoming, nearly 10% of the injected carbon dioxide is predicted to dissolve in one year [ABSTRACT FROM AUTHOR]

The dynamic properties of freestanding rock landforms are a function of fundamental material and mechanical parameters, facilitating noninvasive vibration‐based structural assessment. Characterization of resonant frequencies, mode shapes, and damping ratios, however, can be challenging at culturally sensitive geologic features, such as rock arches, where physical access is limited. Using sparse ambient vibration measurements, we describe three resonant modes between 1 and 40 Hz for 17 natural arches in Utah spanning a range of lengths from 3–88 m. Modal polarization data are evaluated to combine field observations with 3‐D numerical models. We find outcrop‐scale elastic moduli vary from 0.8 to 8.0 GPa, correlated with diagenetic processes and identify low damping at all sites. Correlation of dense‐array measurements from one arch validates predictions of simple bending modes and fixed boundary conditions. Our results establish use of sparse ambient resonance measurements for structural assessment and monitoring of arches and similar freestanding geologic features worldwide. Plain Language Summary: Natural rock arches vibrate under ambient conditions with a unique set of frequencies controlled by geometry, host material, and interactions with nearby bedrock. Recent rockfall events at well‐known arches in Utah have highlighted the need to develop noninvasive assessment methods to better understand how these sensitive landforms evolve. To reduce site impacts, we employed limited instrumentation to measure ambient vibrations of 17 arches across Utah for identification of resonant frequencies. We combine direct observations with predictive numerical models to visualize resonant mode shapes and describe the controlling material properties and structural boundaries. In defining the first three modes of each site, we are able to characterize dynamic properties at arches encompassing several geologic formations and a range of length scales. These results establish a versatile method for structural evaluations of arches and other significant freestanding geologic features. Key Points: Single‐station ambient vibration data and numerical modeling describe the dynamic response of natural arches with limited site accessDense seismic array directly resolves resonant mode shapes, validating predictions of simple bending modes and fixed boundary conditionsSandstone arches in Utah resonate between 1 and 40 Hz, exhibit low damping, and have stiffness that vary with diagenetic conditions [ABSTRACT FROM AUTHOR]

Dynamic topography due to mantle flow contributes to shaping Earth's evolving landscapes by affecting sediment routing, which has rarely been explored in source‐to‐sink contexts. Here we design a generic model to investigate the impact of dynamic topography on both landscape evolution and stratigraphic formations. An imposed wave of dynamic topography propagates laterally under a fixed continent, exerting transient surface uplift and subsidence. We find that a migrating dynamic topography can induce significant drainage reorganizations and affect sediment routing from source to sink. Variations in sediment supply driven by the lateral migrating dynamic topography contribute to the formation of diachronous unconformities along the margin. The predicted sediment flux histories are then put into perspective with the Cretaceous sedimentary records along the Southern African margins. Finally, we demonstrate that correlating offshore depositional hiatuses and unconformities has the potential to constrain the spatiotemporal evolution of past dynamic topography events. Plain Language Summary: Convective motion within Earth's interior result in transient uplift and subsidence of the surface is called dynamic topography. This process slowly shapes landscapes over millions of years and identifying its fingerprints in the rock record remains a challenge. This study uses numerical modeling to investigate the erosional and depositional response of landscapes to sea level change and to mantle flow. We show that unlike sea level change, dynamic topography reorganizes river flows and changes sediment supply to offshore regions, generating various stratal patterns. We model a simple circular landscape that evolves similarly to the southern African landscape between 140 and 66 million years ago and suggest sedimentary fingerprints to link the evolution of the Earth's surface to the dynamics of its deep interior. Key Points: A propagating wave of dynamic topography can induce significant drainage reorganizations and affect sediment routing from source to sinkVariations in sediment supply driven by the migration of dynamic topography can create diachronous unconformities along continental marginsOur model predicts sediment flux histories comparable to that along the Southern African margins during Cretaceous times [ABSTRACT FROM AUTHOR]

The geographical name of Monegros has traditionally been used to describe a high‐quality, dark‐coloured chert originating in a carbonate lacustrine environment, being one of the most important long‐distance tracers in south‐west Europe during prehistory. This chert type outcrops in the Monegros region, situated in the Ebro Basin (north‐eastern Iberia), but not only there, as cherts with the same descriptions are found in other regions, some far from the homonymous area. Nevertheless, prehistorians working on the characterization of lithic sources have frequently used the term 'Monegros' to define this chert, basing their attributions solely on macroscopic descriptions. These are not sufficient as they do not allow cherts from the Monegros region to be distinguished from cherts from other regions. In this study, the area where Monegros cherts outcrop was delimited and fieldwork was carried out to identify the origin of the geological formations and the preserved outcrops. The classic approach has proved to be insufficient for this purpose, so geochemical fingerprinting using energy‐dispersive X‐ray fluorescence (ED‐XRF) spectroscopy was performed. The results obtained after this first geochemical approach show that some differences can be found between the different formations in the Monegros region in terms of their major and minor components. [ABSTRACT FROM AUTHOR]

In the area around Angkor, Cambodia, several ceramics kilns dating from the ninth to 15th centuries ce have been discovered since 1995. The technical, typological and compositional characterization of their production has been one of the main goals of the Cerangkor Project. Samples of green‐glazed 'Kulen‐type' stoneware and non‐glazed stoneware produced in five kiln sites in the Angkor region were analysed chemically by wavelength‐dispersive X‐ray fluorescence spectrometry (WDS‐XRF) and also petrographically. The data indicate that some workshops used similar raw materials for the same types of ceramics, suggesting the exploitation of the same geological formations in the whole region. Several references groups were established for each type of stoneware offering an important database for future provenance studies of sherds from consumption sites. [ABSTRACT FROM AUTHOR]

Intact soil columns can bridge the gap between field studies and idealized laboratory investigations of flow and transport in macropores and fractured media. However, the value of intact column studies is often hampered by shortcomings such as lack of column intactness, small column size, and column rim flow, which can cause serious artifacts and hamper system understanding. The flexible‐wall pressurized large undisturbed column (LUC) method overcomes these limitations and is a valuable approach to analyze fluid flow and solute transport in macroporous and fractured geological formations. The method investigates subsurface processes in complex media, mimicking in situ conditions and facilitating the control of system boundary conditions including effective stress. In recent years, considerable experience has been gained through different applications of the LUC approach. Modeling tools have also been developed for a detailed interpretation of flow and transport processes in LUC systems. This paper describes the steps of the LUC method from column excavation in the field to experimental setup in the laboratory. The description encompasses the key features of the sampling of LUCs in field excavations, the laboratory setup, the procedure for hydraulic and transport experiments, as well as practical challenges and potential issues during operation of an LUC system. Application examples with a fully three‐dimensional numerical model of LUC tracer experiments are also presented to illustrate the quantitative interpretation of transport processes in macroporous clayey tills. Article impact statement: Illustration, discussion, and modeling interpretation of a unique method to investigate flow and transport in macropores and fractured media. [ABSTRACT FROM AUTHOR]

Enterolithic structures are stratigraphically localized folds in gypsum beds found in certain saline evaporitic sedimentary units in a wide variety of basins. Different models of formation have been proposed, all related to inorganic processes. These models include: diagenetic transformation of gypsum beds producing either displacive growth of crystals or volume changes; mechanical folding caused by compressional stress; and folding produced by slumping. The analysis of three Cenozoic evaporite sequences in Spain reveals that none of the previous models explains their origin and existence. In these outcrops, gypsum enterolithic structures occur in horizontal beds with parallel troughs and crests of the folds. They appear in shoreline facies of lacustrine environments and did not undergo major diagenetic transformations after the primary lithification of the original sediment. Based on these observations, together with the study of a modern analogue in Minorca, Spain, a new model is proposed for the genesis of enterolithic structures. This new model is based on the existence of a microbial mat exposed to brine concentration–dilution cycles and strong wind events. The high wind flow events enhanced folding of the microbial mat that became subaerially exposed and lithified due to subsequent evaporation. Therefore, the presence of enterolithic structures could be used as an indicator of shallow water environmental conditions subject to variations in brine concentration in areas with strong wind flow events. Previous studies of some evaporitic successions should be revisited, taking into account the proposed model, which would imply new depositional environment interpretations. At the same time, the proposed model could explain the existence of Kinneyia‐type structures, also known as wrinkle structures, formed beneath microbial mats in peritidal zones. Moreover, considering enterolithic structures as microbially induced sedimentary structures could be useful as evidence of microbial life in the ancient geological record and on other planets such as Mars. [ABSTRACT FROM AUTHOR]

The upper reaches of the Minjiang River are in the eastern margin of the Tibetan Plateau, where active faults are well developed and earthquakes frequently occur. Anomalous climate change and the extremely complex geomechanical properties of rock and soil have resulted in a number of geohazards. Based on the analysis of remote sensing interpretations, geological field surveys, geophysical prospecting and geological dating results, this paper discusses the developmental characteristics of the Gamisi ancient landslide in Songpan County, Sichuan Province, and investigates its geological age and formation mechanism. This study finds that the Gamisi ancient landslide is in the periglacial region of the Minshan Mountain and formed approximately 25 ka BP. The landslide initiation zone has a collapse and slide zone of approximately 22.65×106–31.7×106 m3 and shows a maximum sliding distance of approximately 1.42 km, with an elevation difference of approximately 310 m between the back wall of the landslide and the leading edge of the accumulation area. The landslide movement was characterized by a high speed and long runout. During the sliding process, the landslide body eroded and dammed the ancient Minjiang River valley. The ancient river channel was buried 30‐60 m below the surface of the landslide accumulation area. Geophysical prospecting and drilling observations revealed that the ancient riverbed was approximately 80‐100 m thick. After the dam broke, the Minjiang River was migrated to the current channel at the leading edge of the landslide. The Gamisi ancient landslide was greatly affected by the regional crustal uplift, topography, geomorphology and paleoclimatic change. The combined action of periglacial karstification and climate change caused the limestone at the rear edge of the landslide fractured, thus providing a lithological foundation for landslide occurrence. Intense tectonic activity along the Minjiang Fault, which runs through the middle and trailing parts of the Gamisi ancient landslide, may have been the main factor inducing landsliding. Studying the Gamisi ancient landslide is of great significance for investigating the regional response to paleoclimatic change and geomorphologic evolution of the Minjiang Fault since the late Pleistocene and for disaster prevention and mitigation. [ABSTRACT FROM AUTHOR]

Estimating flow and transport properties of porous media that undergo deformation as a result of applying an external pressure or stress is important to a wide variety of processes, ranging from shale formations into which a fracking liquid is injected to CO2 sequestration in geological formations. We propose a novel model for estimating the effective permeability of such porous media. Given the pore‐size distribution (PSD) of a porous medium before deformation, as well as the Young's modulus of its grains, the model uses Hertz‐Mindlin theory of contact between grains to compute the new PSD that results from applying an external pressure P to the medium and utilizes the updated PSD in the effective‐medium approximation to estimate the effective permeability at P. Comparison between the predictions and experimental data for several types of sandstones indicates excellent agreement between the two. Key Point: This demonstrates the first application of the effective‐media approximation to estimating the permeability of deforming porous media [ABSTRACT FROM AUTHOR]

Earthquakes caused by human activities have been observed for decades. Often these are related to industrial activities pumping fluids into deep geologic formations, like with wastewater disposal. The simplest theory connecting these processes to earthquakes is straightforward: injection leads to fluid pressure changes that either reduce the strength of preexisting faults or generate new faults. In practice, the conditions that lead to induced earthquakes are not always clear in ways that can be generalized. Kao et al. (2018, https://doi.org/10.1029/2018GL079288) show how the distribution of induced earthquakes in Western Canada relate to natural rates of deformation in the crust. Using these new results, they discuss an intriguing paradox: induced seismicity can cause short‐term increases in the seismic hazard that are followed by a period of reduced seismic hazard. Such hazard‐reducing scenarios are plausible but hinge upon simplifying assumptions about how the crust stores and releases strain energy in the form of earthquakes. Key Points: Geodetic data indicate a close relationship between crustal strain rates and induced earthquakesInduced earthquakes might reduce the seismic hazard in the long runHazard‐reducing scenarios hinge critically on a few major assumptions [ABSTRACT FROM AUTHOR]

In geologic media, fluids exist in gas, liquid, and supercritical phases, generating multiphase and multicomponent systems. As fluids migrating through geologic fractures reach the speed of sound, choked flow can be developed in microfractures. To elucidate such choked flow, thermodynamic analysis and numerical simulations were conducted with CO2, H2O, and CO2‐H2O mixtures at various phases ranging from supercritical to gaseous CO2 and liquid H2O. Compressible CO2, with a relatively low speed of sound (~225 m/s at 31.1 °C and 7.38 MPa), demonstrated significant changes in thermodynamic properties with small pressure and temperature variations. In contrast, H2O, having a relatively high speed of sound (1,524 m/s), showed little thermodynamic variation. For CO2‐H2O mixtures, a small addition of CO2 (or H2O) dramatically reduced the speed of sound relative to those for pure H2O or CO2. For an idealized converging‐diverging microfracture with CO2 flow, choked flow and a shock wave were generated as outlet pressure was decreased to less than 6.8 MPa. The H2O flow did not generate choked flow at any outlet pressures. For CO2‐H2O mixtures, choked flow was generated when the CO2 void fraction was greater than 0.7 with an outlet pressure of 6.5 MPa, indicating that presence of H2O inhibited occurrence of choked flow. Choked flow and shock waves can occur in various geologic environments including geologic CO2 sequestration, geothermal energy development, geysers, and volcano eruptions. Key Points: Numerical simulations were performed on CO2, H2O, and CO2‐H2O mixtures to characterize choked flow in microfracturesThe sound speed of the CO2‐H2O mixture is significantly smaller than those of pure CO2 or H2OWhen CO2 is injected to subsurface, choked flow was harder to generate in the CO2‐H2O mixture flow than in CO2 flow [ABSTRACT FROM AUTHOR]

The Zafra de Záncara anticline (also known as the El Hito anticline), located in the Loranca Cenozoic Basin (part of the Tagus Basin, Central Spain), had been studied by several oil companies during the late 1960s and early 1970s. In 2009, within the 'Plan for selection and characterization of suitable structures of CO2 geological storage', this anticline was selected as a potential CO2 storage site. A preliminary three‐dimensional geological model, based on five geological cross sections that were constrained with the interpretation of the available seismic profiles (that are rather old and do not have very good quality), was created. With the aim of improving the geological knowledge of the Zafra de Záncara anticline and helping to investigate the suitability of a nearby anticline, namely La Rambla, as another structural closure that might make it a possible CO2 storage site, a local gravity survey (1 station every km2) was carried out in the area, seven new geological cross sections, based on these existing seismic profiles and field geology, were build, and a new three‐dimensional geological model that included both anticlines, improved through three‐dimensional stochastic gravity inversion, was constructed. The densities needed for the geological formations of the model come from the analysis of rock samples, logging data from El Hito‐1 drillhole and petrophysical information from Instituto Geológico y Minero de España database. The inversion has improved the knowledge about the geometry of the anticlines' traps and seals as well as the geometry of the basement relief and the structural relationship between basement and cover. [ABSTRACT FROM AUTHOR]

The Tongling ore district is one of the most economically important ore areas in the Middle–Lower Yangtze River Metallogenic Belt, eastern China. It contains hundreds of polymetallic copper–gold deposits and occurrences. Those deposits are mainly clustered (from west to east) within the Tongguanshan, Shizishan, Xinqiao, Fenghuangshan, and Shatanjiao orefields. Until recently, the majority of these deposits were thought to be skarn‐ or porphyry–skarn‐type deposits; however there have been recent discoveries of numerous vein‐type Au, Ag, and Pb‐Zn deposits that do not fall into either of these categories. This indicates that there is some uncertainty over this classification. Here, we present the results of several systematic geological studies of representative deposits in the Tongling ore district. From investigation of the ore‐controlling structures, lithology of the host rock, mineral assemblages, and the characteristics of the mineralization and alteration within these deposits, three genetic types of deposits (skarn‐, porphyry‐, and vein‐type deposits) have been identified. The spatial and temporal relationships between the orebodies and Yanshanian intrusions combined with the sources of the ore‐forming fluids and metals, as well as the geodynamic setting of this ore district, indicate that all three deposit types are genetically related each other and constitute a magmatic–hydrothermal system. This study outlines a model that relates the polymetallic copper–gold porphyry‐, skarn‐, and vein‐type deposits within the Tongling ore district. This model provides a theoretical basis to guide exploration for deep‐seated and concealed porphyry‐type Cu (–Mo, –Au) deposits as well as shallow vein‐type Au, Ag, and Pb–Zn deposits in this area and elsewhere. [ABSTRACT FROM AUTHOR]

Analysing S‐wave splitting has become a routine step in processing multicomponent data. Typically, this analysis leads to determining the principal directions of a transversely isotropic medium with a horizontal symmetry axis, which is assumed to be responsible for azimuthal anisotropy, and to the time delays between the fast and slow S‐waves. These parameters are commonly estimated layer‐by‐layer from the top. Errors in layer stripping occurring in shallow layers might propagate to deeper layers. We propose a method for S‐wave splitting analysis and compensation that consists of inverting interval values of splitting intensity to obtain a model of anisotropic parameters that vary with time and/or depth. Splitting intensity is a robust attribute with respect to structural variations and is commutative, which means that it can be summed along a ray (or throughout a sensitivity kernel volume) and can be linearly related to anisotropic perturbations at depth. Therefore, it is possible to estimate anisotropic properties within a geological formation (e.g. the reservoir) by analysing the differences of splitting intensity measured at the top and at the bottom of the layer. This allows us to avoid layer stripping, in particular, for shallow layers where anisotropic parameters are difficult to estimate due to poor coverage, and it makes S‐wave splitting analysis simpler to apply. We demonstrate this method on synthetic and real data. Because the splitting intensity attribute shows usefulness in S‐wave splitting analysis in transversely isotropic media, we extend the splitting intensity theory to lower symmetry classes. It enables the characterization of tilted transversely isotropic and tilted orthorhombic media, opening new opportunities for anisotropic model building. [ABSTRACT FROM AUTHOR]

Penecontemporaneous dissolution has been considered as the dominant origin of reservoir formation, whereas epigenetic dissolution has also played certain roles in the improvement of reservoir capacity in the Upper Cretaceous Mishrif Formation in the Middle East. Here, we report a possible new reservoir origin based on a case study in the Halfaya oilfield of Iraq, that is, facies‐controlled eogenetic karstification. The most representative evidence is that early selective dissolution is not only present in relative high‐energy categories of rocks but also in low‐energy ones in the cored intervals. Meanwhile, the occurrence frequency of karstification varies among different environments and associated lithologies. In grainstones and packstones, spongy‐like dissolution pores and irregular karst channels are widely developed, with fillings and massive plastic breccias. In contrast, in wackestones, lots of high‐angle karst channels are developed based on biological burrows, and the karst is more frequently observed in the shoal environment than in the low‐energy environments. These characteristics are indication of eogenetic karstification. The model of this karstification can be attributed to a multiple superimposition of short‐term exposure during the penecontemporaneous stage and the medium‐term exposure after the shallow burial stage. The karst has impact on reservoir capacity, according to which 3 areas are divided in the increasing order, namely, the tight bedrock area, spongy‐like dissolution pores area, and karst channels and vugs‐filled area, among which the karst channels and vugs‐filled area is the most favourable for oil accumulation. This understanding might be general to the Mishrif reservoirs in the entire Middle East. [ABSTRACT FROM AUTHOR]

At the south‐western margin of the North China Craton (NCC), there existed a lot of Mesoproterozoic strata. However, it is hardly known about the Mesoproterozoic stratigraphic sequence and deep structures of the south‐western part of NCC (most is the Ordos Block) due to the thick Phanerozoic sedimentary cover above the Precambrian basement and strata. Combining the drilling well data, seismic profiles, and outcrops around the whole Ordos Block, it becomes possible to reveal the deep structure and distribution of Mesoproterozoic strata. The distribution and sedimentation of Mesoproterozoic at the southwestern margin of NCC were controlled by a series of NE–SW extension deep faults just existed in Mesoproterozoic Changcheng System and Jixian System. According to the drilling well data, the Changchang System includes several various thickness volcanic rocks, and the stratigraphic sequence and lithological combination are similar to the Yanliao Rift. During the sedimentation from Longjiayuan Formation to Duguan Formation, the water got deeper revealed by the content of Ce element gradually decreasing. However, the content of Ce element unusually increases during the steady subsidence of the Mesoproterozoic basin, while the Xunjiansi Formation sedimented. The deposition of tephra or hydrothermal might contribute a lot to the increase of the Ce element's content. Besides that, numerous soft‐sediment deformation structures developed in carbonate rocks of Mesoproterozoic Xunjiansi Formation at the south‐western margin of NCC. What's more, the Xunjiansi Formation with soft‐sediment deformation structures can be regarded as a marker bed for the comparison with the Wumishan Formation in Yanliao Rift. Besides that, there is a set of residual sandstone conformably covered the dolomite of Mesoproterozoic Fengjiawan Formation. It corresponds with Xiamaling Formation of Building System in Yanliao Rift System based on the stratigraphic sequence and relative sedimentary time limited by the youngest zircon U–Pb age peak 1,511.1 ± 10 Ma (n = 7) and single zircon U–Pb age 1,436 ± 28 Ma. Therefore, the south‐western part of NCC have high similarity of stratigraphic sequence and sedimentary framework with Yanliao Rift. Moreover, the development of volcanic rocks in Changcheng System, soft‐sediment deformation structures, and Ce abnormal increasing in Xunjiansi Formation might suggest that there developed an active Mesoproterozoic Rift in the south‐western part of the NCC similar to Yanliao Rift. Generally, the south‐western part of NCC share similar tectonic background with Yanliao Rift. [ABSTRACT FROM AUTHOR]

The Zhunmubutai ophiolitic mélange is a newly discovered ophiolite suite located between the Solonker‐Linxi ophiolite belt and the Erenhot‐Hegenshan‐Xi‐Ujimqin ophiolite belt, the central part of Xilinhot Microcontinent (XLMC). It was composed of plagiogranite, pyroxene peridotite, pillow basaltic andesite, and associated mafic rocks and surrounded by a quartz diorite pluton and mélange zone containing sandstones and slates of Early Permian Shoushangou Formation. In this study, zircon grains from a quartz diorite and a plagiogranite yield 206Pb/238U ages of 313 ± 1 Ma (MSWD = 1.60, n = 20) and 328 ± 1 Ma (MSWD = 0.9, n = 93), respectively. Sixty‐four zircons from the slate yielded ages ranging from 307 to 2,313 Ma, and with a peak at 340 Ma. These data indicate the Zhunmubutai ophiolitic mélange formed 300 to 340 Ma. The Zhunmubutai plagiogranites that have low contents of K2O (0.07–0.33 wt.%), K2O/Na2O (0.02–0.09), and Rb/Sr (0.01–0.05) show an oceanic plagiogranites affinity. They are also characterized by low contents of TiO2, Nd, Ta, and significant LREE enrichment. Furthermore, the εHf (328 Ma) values range from 14.23 to 18.87. These features suggest that the plagiogranite was originated by the anatexis of amphibolites and with crustal contamination. Combined with previous studies, suggest that the Zhunmubutai ophiolitic mélange may have formed in an extensional environment during the early stages of opening of an ocean basin. [ABSTRACT FROM AUTHOR]