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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]

Introduction: The geological record of the formation and differentiation of our planet has been destroyed by its subsequent evolution, but extremely rare clues may be obtained from other terrestrial planets. Mars provides a unique and accessible example of an early evolutionary path corresponding to that, inaccessible, of our own world. We can investigate it with spacecraft, and samples are available for in-depth analysis on Earth in the form of martian meteorites. So far, the only available martian samples that appear to have recorded the early conditions and the evolution of the planet until the present time are Northwest Africa (NWA) 7034 and its paired stones, nicknamed "Black Beauty". This regolith breccia has been ejected a few million years ago by the formation of a large impact crater, and contains the oldest martian igneous material ever dated: ~4.5 Ga old [1-4]. However, its source and geological context have so far remained unknown. and with it, a region where the earliest geological records of the planet [1-4] are exposed on the surface. Knowing this source region would provide insights into early Mars geological history and crustal extraction [1-4]. This source region may therefore become a high-priority target for detailed orbital analyses and in-situ exploration [5]. Constraints on the meteorite launch site: Following a hypervelocity impact, ejecta materials moving faster than the escape velocity (5 km/s) may get through the martian atmosphere and continue their course into interplanetary space to become martian meteorites [6]. Slower debris fall back on the surface in a radial pattern or ray around the primary crater, forming secondary craters. The presence of 100 meter-size secondaries attests to the freshness of their associated primary craters [7]. Using the size and spatial distribution of more than 90 million impact craters >50 m (both primaries and secondaries) detected using a Crater Detection Algorithm (CDA) [7-8] on the whole surface of Mars from the global Context Camera (CTX) mosaic [9], a previous work [7] identified ray systems of secondary craters <150 m associated with 19 large primary craters, potential source of the ejection of martian meteorites. Here we compare the abundance of K and Th [10-11] as well as the magnetic field intensity and the magnetization of the surface of Mars derived from orbital measurements [12] at the immediate vicinity of each crater candidate with those of the breccia. We also compare the geological context of each of the crater candidates with the chronology and the lithology of the meteorite [e.g. 1-3, 13-14]. The ejection site for Black Beauty: Among the 19 crater candidates investigated, we found that only one match with the characteristics of the meteorite: a 10 km crater located in the north-east of the Terra Cimeria - Sirenum (TCTS) region, between Hesperia Planum and the Tharsis bulge. Our work suggests that clasts contained in the regolith breccia are representative of the TCTS province, making this region a relic of the early crustal processes on Mars [e.g. 15], and thus, a region of high interest for future missions. Details on the identification of the crater source of this unique meteorite, as well a its geological context and broader implications for early crustal processes on Mars will be presented at the conference. [ABSTRACT FROM AUTHOR]