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Due to the inherent unpredictability of geological conditions, tunnelling operations are often at risk of encountering water inrushes. Such incidents can lead to construction delays, impose financial strains and pose significant safety threats to the workers involved. Water‐bearing geological formations are the main triggers for such incidents, with factors such as the positioning, water quantity and permeability distribution of these formations being key to predicting the occurrence and severity of water inrush disasters. By leveraging the complex interplay among relaxation time, P‐wave velocity and permeability within the rock's physical properties, a series of indoor tests were conducted on 40 artificial reef limestone cores to extract the necessary parameters. Through the analysis of the data, the comprehensive permeability prediction model was established, and the correlation coefficient was 0.9420 between the model's predictions and actual measurements. At the same time, through theoretical and mechanism analysis, the relationship between permeability and relaxation time and the relationship between permeability and P‐wave velocity were analysed. Finally, 10 natural reef limestone samples were used to verify the accuracy of the model. The prediction model enables an accurate evaluation of tunnel permeability, thus providing a scientific basis for the mitigation of tunnel water inrush hazards. [ABSTRACT FROM AUTHOR]

Barium (Ba) dissolution and mobilization in groundwater are predominantly controlled by sulfate because of the low solubility of barium sulfate (BaSO4) minerals. Naturally present at low concentrations in groundwater, elevated concentrations of Ba can occur as a result of anthropogenic activities, including use of barite in drill operations, and geogenic sources such as leaching from geological formations. No toxicity data exist for Ba with groundwater organisms (stygofauna) to assess the risk of elevated Ba concentrations. The present study measured Ba toxicity to two stygobiont Cyclopoida species: one collected from Wellington and the other from Somersby, New South Wales, Australia. Toxicity was measured as cyclopoid survival over 2, 4, 7, 14, 21, and 28 days in waters of varying sulfate concentration (<1–100 mg SO4/L). When sulfate was present, dissolved Ba concentrations decreased rapidly in toxicity test solutions forming a BaSO4 precipitate until dissolved sulfate was depleted. Barium in excess of sulfate remained in the dissolved form. The toxicity of Ba to cyclopoids was clearly attributed to dissolved Ba. Precipitated Ba was not toxic to the Wellington cyclopoid species. Toxicity values for dissolved Ba for the Wellington and Somersby cyclopoid species included a (21‐day) no‐effect concentration of 3.3 mg/L and an effective concentration to cause 5% mortality of 4.8 mg/L (at 21 days). Elevated dissolved Ba concentrations due to anthropogenic and/or biogeochemical processes may pose a risk to groundwater organisms. Further toxicity testing with other stygobiont species is recommended to increase the data available to derive a guideline value for Ba that can be used in contaminant risk assessments for groundwaters. Environ Toxicol Chem 2024;00:1–14. © 2024 The Author(s). Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

The Carpathian belt is one of Europe's major metallogenic provinces, where magmatic ore mineralization is associated with the past subduction environment. The upper crust is mapped for the first time in the Northeast Carpathian Volcanic Arc using magnetotelluric data inversion. The obtained 3‐D electrical resistivity model is interpreted in conjunction with geological information and magnetic anomaly data. The model illustrates the deep magmatic plumbing system including kilometer‐scale plutonic bodies at a depth of 2–7 km. The model implies that the transport of magma and fluids in the uppermost crust was controlled by pre‐existing faults and décollement horizons. Present ore mineralization, mined since historical times, can be attributed to an electrically conductive conduit that is mapped from the surface to a depth of about 30 km. It is suggested that this conduit connected a shallow magmatic chamber to a deep source region in the southeast during late Miocene time. An observed northwest deflection of the deep magmatic conduit at a depth of more than 10 km may explain the spatial gap in the distribution of the Miocene volcanic activity along the Eastern Carpathians. Plain Language Summary: The Carpathian Mountains have long been exploited for their metal ore deposits, which have been associated with the subduction of tectonic plates. Studying the natural variations of the regional electric and magnetic fields, we estimate the distribution of subsurface electrical resistivity. Subsurface electrical structures are interpreted as deep magma systems and large plutonic bodies. The interpretation implies that regional volcanic activity has been controlled by faults, large fractures in geologic formations, and detached strata. Specifically, historic mining can be attributed to a large conductive body that can be mapped from surface to about 30 km. Data suggest that this body, which could represent a pathway of magmatic fluids, connects to a deep, southeastern mantle source region. Key Points: 3‐D magnetotelluric survey in northeast Carpathian Mountains elucidates the structure of the Miocene volcanic provinceNew data reveal shallow magmatic‐hydrothermal system connected to a deep source region via an inclined conductive conduitCenturies‐old mines align with an electrically conductive layer interpreted as a clay alteration related to hydrothermal activity [ABSTRACT FROM AUTHOR]

Geological formations with fractures are frequently encountered in various research fields. Accurately characterizing these fractured media is of paramount importance when it comes to tasks that demand precise predictions of liquid flow and solute transport within them. Since directly measuring fractured media poses inherent challenges, data assimilation (DA) techniques are typically employed to derive inverse estimates of media properties using observable state variables. Nonetheless, the considerable difficulties arising from the strong heterogeneity and non‐Gaussian nature of fractured media have diminished the effectiveness of existing DA methods. In this study, we formulate a novel DA approach known as parameter estimator with deep learning (PEDL) that harnesses the capabilities of DL to capture nonlinear relationships and extract non‐Gaussian features. To evaluate PEDL's performance, we conduct three case studies, comprising two numerical cases and one real‐world case. In these cases, we systematically compare PEDL with three widely used DA methods: ensemble smoother with multiple DA (ESMDA), iterative local updating ES (ILUES), and ES with DL‐based update (ESDL). Notably, in the problems characterized by highly non‐Gaussian features, ESMDA and ILUES produce significantly divergent results. Conversely, employing the DL‐based update, ESDL demonstrates improved performance. However, its estimation uncertainty remains high, potentially attributable to ESDL's updating mechanism. Comprehensive analyses confirm PEDL's validity and adaptability across various ensemble sizes and DL model architectures. Moreover, even in scenarios where structural difference exists between the accurate reference model and the simplified forecast model, PEDL adeptly identifies the primary characteristics of fracture networks. Key Points: A deep learning‐based data assimilation method, named parameter estimator with deep learning (PEDL), is proposed to characterize fractured media with highly non‐Gaussian featuresPEDL outperforms three popular data assimilation methods based on deep learning or the Kalman formulaComprehensive analyses confirm PEDL's validity and adaptability across various ensemble sizes and DL model architectures [ABSTRACT FROM AUTHOR]

The Archean Superior craton was formed by the assemblage of continental and oceanic terranes at ∼2.6 Ga. The craton is surrounded by multiple Proterozoic mobile belts, including the Paleoproterozoic Trans‐Hudson Orogen which brought together the Superior and Rae/Hearne cratons at ∼1.9–1.8 Ga. Despite numerous studies on Precambrian lithospheric formation and evolution, the deep thermochemical structure of the Superior craton and its surroundings remains poorly understood. Here we investigate the upper mantle beneath the region from the surface to 400 km depth by jointly inverting Rayleigh wave phase velocity dispersion data, elevation, geoid height and surface heat flow, using a probabilistic inversion to obtain a (pseudo‐)3D model of composition, density and temperature. The lithospheric structure is dominated by thick cratonic roots (>300 km) beneath the eastern and western arms of the Superior craton, with a chemically depleted signature (Mg# > 92.5), consistent with independent results from mantle xenoliths. Beneath the surrounding Proterozoic and Phanerozoic orogens, the Mid‐continent Rift and Hudson Strait, we observe a relatively thinner lithosphere and more fertile composition, indicating that these regions have undergone lithospheric modification and erosion. Our model supports the hypothesis that the core of the Superior craton is well‐preserved and has evaded lithospheric destruction and refertilization. We propose three factors playing a critical role in the craton's stability: (a) the presence of a mid‐lithospheric discontinuity, (b) the correct isopycnic conditions to sustain a strength contrast between the craton and the surrounding mantle, and (c) the presence of weaker mobile belts around the craton. Plain Language Summary: We introduce a new model of the temperature and composition of the Superior Craton, a stable and ancient (>2.5 billion years old) geological formation, and its neighboring areas, by using an advanced and novel imaging technique. The central aim of the study is to use the present‐day structure (from the surface to 400 km depth) to understand how the craton's lithosphere (the rigid outer layer of the Earth) has evolved over time, and how its deep roots have persisted over billions of years of geological processes. The Superior Craton displays well‐preserved cores with a distinct chemical composition beneath its eastern and western arms, which likely contribute to its long‐term preservation. Isopycnicity (a state of density equilibrium) within the lithosphere is a likely controller of long‐term stability. Additionally, the presence of layering in the lithosphere and weaker structures (e.g., mountain belts, rifts, hotspot tracks) surrounding the edges of the craton emerge as critical factors contributing to the resilience and endurance of the Superior Craton's lithosphere. These findings significantly advance our understanding of the mechanisms governing the evolution and stability of cratonic regions. Key Points: First integrated multi‐observable probabilistic thermochemical model of the lithosphere beneath the Superior craton and environsThe Superior craton shows well‐preserved depleted cores beneath its eastern and western armsLong‐term craton stability is likely controlled by isopycnicity, and the presence of mid‐lithospheric discontinuities and mobile belts [ABSTRACT FROM AUTHOR]

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]

High‐resolution 2D and 3D data remotely acquired by SuperCam's Remote Micro‐Imager and Mastcam‐Z aboard the Perseverance rover enabled us to characterize the stratigraphic architecture and sedimentary record of the Kodiak butte, an isolated remnant of the western delta fan of Jezero crater. Using these data, we build up on previous interpretations of the butte interpreted as a prograding Gilbert‐type deltaic series. We characterize three individual stratigraphic Units 0 to 2 on the eastern and northern faces of the butte. Each Unit displays the same vertical succession of prodeltaic/lacustrine bottomsets, delta slope toesets and foresets, and fluvially influenced topsets of a deltaic plain with a braided river pattern, shown by 11 individual sedimentary facies. We infer that these individual Units record the formation of three distinct deltaic mouth bars successively across time and space. For the first time on another planet than Earth, we are able to construct a precise sequence stratigraphic framework to highlight lake‐level fluctuations at the time the Kodiak butte was emplaced, during the latest stages of deltaic activity. We identify four hydrogeological cycles indicated by alternating rises and falls of the lake‐level on the order of 5–10 m. These were most probably linked to climatic events and variations controlling lake water inputs in probable relation to an astronomical control. Plain Language Summary: Kodiak butte is an isolated remnant of the main western sedimentary fan of Jezero crater. It displays the characteristic structures of a Gilbert‐type delta, a structure that shows deposition of fluvial material into a standing body of water, here interpreted to be a lake within Jezero crater. 11 individual sedimentary facies (textures, grain‐sizes, and structures) of the rocks exposed at Kodiak suggest that the depositional environments ranged from the fluvial plain to a steep subaqueous slope and into the bottom of the shallow Jezero lake. Our observations further show that Kodiak butte is organized into three distinct stratigraphic Units (0–2), each displaying the same vertical succession of bottomsets, toesets, foresets and topsets. This architecture is interpreted as reflecting three distinct deltaic packages, formed consecutively and not at the same time. Using these facies and stratigraphic architecture data, we are able for the first time on another planet than Earth, to precisely construct a sequence stratigraphic framework for the formation of Kodiak. This framework illustrates with unprecedented precision successive episodes of rises and falls of the paleo‐lake‐level (in the order of 5–10 m) involved in the construction and evolution of the western Jezero delta. Key Points: New observations on the Kodiak delta remnant were carried out to characterize its detailed facies and stratigraphic architectureThree deltaic mouth bars are identified showing 4D succession of depositional settings ranging from deltaic plain to slope to shallow lakeThe first ever sequence stratigraphic framework on Mars shows four cycles of alternating rises and falls of the lake‐level within 5–10 m [ABSTRACT FROM AUTHOR]

Progressive climate change may have unpredictable consequences for the Arctic environment. Permafrost catchments off the west coast of Svalbard, described as "thin" and "warm," are particularly sensitive to climate change. The interdisciplinary research on the hydrochemical response of surface and underground water functioning within a small permafrost catchment area focused on the determination of the impact of meteorological conditions (temperature (T), precipitation (P)) on the mean daily discharge (Q), and the lowering of the groundwater table (H). We determined physical and chemical properties (pH and SEC) and concentrations of major elements (Ca, Mg, Na, K) and 23 trace elements (i.a. Cd, Cu, Hg, Pb, Zn) in 280 water samples. The results of the correlation matrix showed that an increase in the average air temperature in the summer of 2021 had a significant impact on the hydrochemistry of both types of waters operating in the catchment. In response to increase in T, the lowering of the H (0.52 < r < 0.66) and a decrease in Q (−0.66 < r < −0.68) were observed what in consequence also leads to changes in water chemistry. The principal component analysis (CA) indicates that chemical weathering and binding of elements to DOC are processes influencing water chemistry. Results of statistical analysis showed that the resultant of the hydrometeorological conditions that prevailed in that season and the type of geological formations on which they were located had a significant impact on the water chemistry at individual measurement points. Significant differences in the concentrations of elements between points on the same geological formations were also found. [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]

Zircon U‐Pb‐He double dating (ZDD) provides the opportunity to derive high temperature crystallization ages and low temperature cooling ages from the very same mineral grain, making it especially attractive for zircon provenance studies. We present the combination of in situ detrital zircon U‐Pb‐He double dating and Raman spectroscopy‐based heavy mineral analysis on different tributaries of the Inn river system applying a new grain embedding technique. The Inn river catchment drains a well‐studied complex nappe pile of the Eastern Alps exposing Austroalpine and Penninic crystalline basement rocks. Igneous formations of different emplacement ages, as well as various metasedimentary units, have experienced Alpine and diverse pre‐Alpine metamorphic overprints. This makes the area ideally suited for testing the sensitivity and potential of ZDD for fingerprinting various lithologically contrasting units with contrasting thermal histories. Results demonstrate that both high‐ and low‐temperature age distributions reflect the major sources and thermotectonic pulses, respectively. More specifically, the rocks of the Tauern Window with Miocene (U‐Th)/He ages as well as the Permian metagranitoids from the Tauern and the Err‐Bernina nappe in the uppermost Inn valley are recorded in the downstream Inn sample. The main mass of zircons in the lower Inn, however, derives from the Ötztal and Silvretta crystalline basement rock with Cadomian U‐Pb and Cretaceous (U‐Th)/He ages. The abundance of heavy minerals derived from metamafic formations shows no correlation to the area of such lithologies on the catchments and the different zircon fertility resulted in the overrepresentation of zircon U‐Pb ages from the Variscan igneous suites. Plain Language Summary: The provenance analysis of sediments addresses the question of their origin, which geological formations were the sources of for example, sand bodies. For this so‐called heavy minerals are used that are specific for some rock types and help identify the major lithologies of the source region. The other method is the determination of the age of the detrital zircon crystals that commonly occur in many rock types and sand samples. In our study, we used a relatively new method that determines both the crystallization age and the cooling age in each individual zircon crystal that is highly specific for the source formations of the sediment. Both the heavy mineral analysis and the zircon "double dating" technique were performed on sand samples from the Alpine Inn river to test the reliability of these methods as the catchment of the river is well known and thus it can be used as a reference region. Key Points: Detrital zircon U‐Pb‐He double dating (DD) can accurately specify the sources of sediment—our test performed on well‐studied Alpine catchmentsCombination of DD and Raman‐based heavy mineral analysis applied to modern sands of the Alpine Inn riverComparison of predicted and measured detrital mineralogy and age spectra [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]

This work is focused on the Almonte‐Marismas aquifer located within Doñana Natural Space (SW Spain); this aquifer is threatened by droughts, irrigation‐driven groundwater overexploitation, urban use, and the potential reactivation of gas extraction and storage projects. We present ground deformation measurements from Sentinel‐1 Interferometric Synthetic Aperture Radar (InSAR) data ranging from 1 to 2.5 cm, covering ∼2,500 km2 from 2014 to 2020. Detecting spatially distributed ground deformation over this agricultural area is challenging due to the low‐coherence radar signals; consequently, the ground movement results are on the same order of magnitude as the errors associated with InSAR data. We have approached this issue by considering auxiliary information such as groundwater levels, climatic time series, and pumping rates and analyzing their spatio‐temporal connections to ground displacements. We correlate InSAR and hydrogeological information through wavelet analysis, developing a Python package that allows applying the same methodology in other similar study areas. For the first time in the Doñana area, a significant relationship between distances to pumping wells and the displacement extent is detected. Moreover, other subsidence‐related triggering factors are identified, such as the soil moisture balance, clay shrinking‐swelling processes, and creep of geological formations. These results are highly valuable to support aquifer management decisions in the Doñana Natural Space; in this border region, three groundwater bodies were officially declared overexploited in 2020. Our findings provide a ground motion baseline assessment to help differentiate historical variations from any future anthropogenic effect in this complex marsh land ecosystem. Plain Language Summary: This work is focused on Doñana Natural Space (SW Spain), which integrates the Doñana National Park and the Doñana Natural Park in a single space. Doñana has acquired the highest protected area categories that a natural area can receive from international conservation organizations. However, Doñana's ability to support biodiversity is under constant threat due to droughts, groundwater overexploitation for irrigation, urban use, and the reactivation of a gas extraction and storage project. This study presents ground deformation measurements in the Doñana area derived from Earth observation data ranging from 1 to 2.5 cm from 2014 to 2020. The work relates ground displacement, groundwater and climatic information through mathematical tools. For the first time in the Doñana area, a significant relationship between distances to pumping wells and the displacement extent is detected. These results are highly valuable to support aquifer management decisions in the Doñana Natural Space. Our findings provide a ground motion baseline assessment that will help differentiate historical variations from any future anthropogenic effect in this complex marsh land ecosystem. Key Points: Integrated Interferometric Synthetic Aperture Radar and hydrogeological analysis has shown displacements up to 2.5 cm/year on the aquifer that hosts the Doñana Natural SpaceWavelet method with a new Python package allows for integrated displacement, groundwater level, climatic and pumping time series analysesThe results provide a ground motion baseline to differentiate natural variations from future anthropogenic effects in the Doñana area [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 Mars 2020 Perseverance rover landed in Jezero crater on 18 February 2021. After a 100‐sol period of commissioning and the Ingenuity Helicopter technology demonstration, Perseverance began its first science campaign to explore the enigmatic Jezero crater floor, whose igneous or sedimentary origins have been much debated in the scientific community. This paper describes the campaign plan developed to explore the crater floor's Máaz and Séítah formations and summarizes the results of the campaign between sols 100–379. By the end of the campaign, Perseverance had traversed more than 5 km, created seven abrasion patches, and sealed nine samples and a witness tube. Analysis of remote and proximity science observations show that the Máaz and Séítah formations are igneous in origin and composed of five and two geologic members, respectively. The Séítah formation represents the olivine‐rich cumulate formed from differentiation of a slowly cooling melt or magma body, and the Máaz formation likely represents a separate series of lava flows emplaced after Séítah. The Máaz and Séítah rocks also preserve evidence of multiple episodes of aqueous alteration in secondary minerals like carbonate, Fe/Mg phyllosilicates, sulfates, and perchlorate, and surficial coatings. Post‐emplacement processes tilted the rocks near the Máaz‐Séítah contact and substantial erosion modified the crater floor rocks to their present‐day expressions. Results from this crater floor campaign, including those obtained upon return of the collected samples, will help to build the geologic history of events that occurred in Jezero crater and provide time constraints on the formation of the Jezero delta. Plain Language Summary: The Mars 2020 Perseverance rover, along with the Ingenuity Helicopter technology demonstration, landed in Jezero crater, Mars on 18 February 2021. Here, we detail results from the first science campaign of the mission, the purpose of which was to explore the enigmatic Jezero crater floor. By the end of the campaign, Perseverance traversed more than 5 km, created seven abrasion patches, and sealed a total of nine samples and a witness tube for return to Earth. Analysis of the rocks in the crater floor revealed two distinct geologic formations, named the Máaz and Séítah formations. Both formations were determined to be igneous in origin, the former likely from a series of lava flows and the latter formed from a slowly cooling melt or magma body. The composition of the Máaz and Séítah formation rocks also indicate that they experienced significant alteration from water in the past, consistent with Jezero crater having once been filled with water. Results from Perseverance's Jezero crater floor campaign, including those obtained upon return of the collected samples to Earth, will help build the geologic history of Jezero crater and reveal its past habitability. Key Points: The Máaz and Séítah formations are igneous, with Séítah representing olivine‐rich cumulates and Máaz representing separate lava flowsCrater floor rocks have been variably altered to produce carbonates and other alteration minerals during multiple aqueous episodesPost‐emplacement processes tilted these rocks near the Máaz‐Séítah contact, and erosion produced varied textures and olivine‐rich regolith [ABSTRACT FROM AUTHOR]

We use a scaling relationship between fault length and scalar moment to predict seismicity from the Cerberus Fossae graben using shear modulus and fault lengths. Cerberus Fossae is 20–40° (1,200–2,300 km) from the InSight lander and matches the location of 21 recorded seismic events with Mw ≥ 3. These unique seismic observations make an ideal laboratory to test our method of predicting seismicity on another planet using surface fault observations. Terrestrial faults have observed patterns of rupture depth distributions and segmentation. We use these patterns and magnitudes of detected marsquakes to predict moment release of events in Cerberus Fossae over a range of plausible Martian rupture vertical slip extents (VSEs) of 2, 20, and 40 km, which are rooted in estimates of crustal thickness, elastic thickness, and seismicity depth. We sum individual events for each case to determine cumulative moment release and use deformation duration to determine annual moment release. Predicted seismicity rates are dependent on the duration of deformation, which in this case is well constrained to 2–10 Ma. We compare our results to events recorded at Cerberus Fossae by InSight and find that seismicity rates for the cases with a 40 km maximum VSE or no limit on VSE are within an order of magnitude of observed seismicity. Faults with maximum VSEs of 2 km best match observed magnitudes. Our approach, using only observed fault lengths, segmentation, seismogenic thickness estimates, and deformation duration, produces seismicity estimates that are as accurate as methods that take rupture offset into account. Plain Language Summary: We develop a method to estimate the magnitudes and frequencies of quakes on Mars in the Cerberus Fossae region using a scaling relationship between fault length and quake magnitude. Our method estimates quake magnitude for each fault length, and ultimately estimates cumulative seismic moment release, or total energy released by the formation of the geologic structure. We calculate seismicity rate by dividing the cumulative moment release by the time of deformation for the geological structure. Our method to estimate seismicity requires fewer assumptions and assumed geophysical constants than previously proposed methods. We use Leonard's (2010, https://doi.org/10.1785/0120090189) aspect ratio of fault length and width. Thus, a maximum faulting depth informs the maximum vertical slip extent (VSE), which in turn limits the maximum fault length and the maximum allowable quake magnitude. Segmentation patterns of the faults inform the magnitude‐frequency distribution of marsquakes but do not account for a high enough occurrence of small quakes. Resulting seismicity rates are within an order of magnitude of what has been measured by the InSight seismometer with a VSE of 40 km or no VSE, and marsquake magnitudes are best represented by a VSE of 2 km. Key Points: We estimate seismicity using a fault length‐moment release scaling relationship. Our results align with InSight seismometer observationsMarsquake magnitudes are limited by vertical slip extents, which are constrained by likely faulting depthsMarsquake magnitude distribution is constrained by segmentation patterns of the graben. Seismicity rate is constrained by deformation time [ABSTRACT FROM AUTHOR]

Injecting CO2 into deep geologic formations for storage purposes induces large pressure build‐up that risks caprock integrity. Naturally occurring faults or pressure‐induced fractures in the caprock can act as conductive leakage pathways resulting in potential contamination of the overlying shallow aquifers. Previous studies explored using brine extraction to manage such elevated pressure in the storage formation. In this paper, we extended the use of this technique to control far‐field brine leakage. Extraction wells are placed in the storage zone to reduce the leakage flow through reversing the pressure‐gradient locally, while minimizing the brine concentrations in the escaped‐fraction by utilizing the dilution capacity of the overlying formations. The developed approach incorporated the Genetic Algorithm with transport model simulations to optimize well‐placements and extraction‐rates. An approximately 8m long intermediate‐scale tank designed to mimic brine leakage migration in the field was used to validate this approach as field data are not available. We further evaluated the approach numerically using a hypothetical leakage scenario at the Vedder storage formation in San‐Joaquin basin to assess its practicality for field implementation. The results showed that storage zone heterogeneity and fractures' permeabilities can significantly affect the optimum locations and pumping rates of the extraction wells. Brine leakage can be controlled by extracting a native‐brine volume less than 50% of the injected CO2 volume. The target concentrations in the shallow aquifer determines the extraction rates required to control a leakage through a fracture or a buried thrust fault. The study is useful to develop remediation strategies for carbon storage operations. © 2022 Society of Chemical Industry and John Wiley & Sons, Ltd. [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]

The Mars Science Laboratory rover, Curiosity, explored the clay mineral‐bearing Glen Torridon region for 1 Martian year between January 2019 and January 2021, including a short campaign onto the Greenheugh pediment. The Glen Torridon campaign sought to characterize the geology of the area, seek evidence of habitable environments, and document the onset of a potentially global climatic transition during the Hesperian era. Curiosity roved 5 km in total throughout Glen Torridon, from the Vera Rubin ridge to the northern margin of the Greenheugh pediment. Curiosity acquired samples from 11 drill holes during this campaign and conducted the first Martian thermochemolytic‐based organics detection experiment with the Sample Analysis at Mars instrument suite. The lowest elevations within Glen Torridon represent a continuation of lacustrine Murray formation deposits, but overlying widespread cross bedded sandstones indicate an interval of more energetic fluvial environments and prompted the definition of a new stratigraphic formation in the Mount Sharp group called the Carolyn Shoemaker formation. Glen Torridon hosts abundant phyllosilicates yet remains compositionally and mineralogically comparable to the rest of the Mount Sharp group. Glen Torridon samples have a great diversity and abundance of sulfur‐bearing organic molecules, which are consistent with the presence of ancient refractory organic matter. The Glen Torridon region experienced heterogeneous diagenesis, with the most striking alteration occurring just below the Siccar Point unconformity at the Greenheugh pediment. Results from the pediment campaign show that the capping sandstone formed within the Stimson Hesperian aeolian sand sea that experienced seasonal variations in wind direction. Plain Language Summary: The Mars Science Laboratory rover, Curiosity, explored a valley called Glen Torridon on the lower slopes of a sedimentary mountain within Gale crater, Mars, between January 2019 and January 2021. The rocks within this shallow valley are part of a sequence of rock layers whose mineral composition could imply a transition from a wetter to drier environment more than 3 billion years ago. This paper reports on the exploration campaign designed to understand the local geology, document evidence of past climate change, and investigate if the ancient environments may have been amenable to biological activity. Curiosity found that many rocks were deposited in the bottom of a lake, but also that river deposits occur frequently in this area, suggesting that the environmental conditions changed through time. Curiosity observed evidence for multiple cycles of water interacting with the sediments that chemically changed the elemental and mineralogical compositions of the rock layers. Curiosity collected 11 drill holes over the course of the campaign and found abundant clay minerals, as predicted, as well as a wide variety of organic molecules, suggesting that the ancient environment contained many of the necessary conditions to support life. Key Points: Sedimentary facies within Glen Torridon record a transition from low‐energy lacustrine mudstones to higher‐energy fluvial sandstonesGlen Torridon hosts the highest clay mineral abundances observed thus far by Mars Science Laboratory (MSL) while remaining in family with the Mount Sharp groupGlen Torridon drill samples contain the greatest diversity of organic compounds yet detected by the MSL mission [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 mineral trapping of CO2 in geological formation is the most promising and safe mechanism for permanent carbon storage. The chlorite shows a great influence on the form and capacity of carbon storage in sandstone reservoirs due to its wide distribution and strong chemical activity. In this paper, to better understand the dissolution process of chlorite after the injection of CO2 and its potential impacts on carbon mineral trapping patterns, two sets of hydrothermal batch reactions toward chlorite and CO2 fluid are conducted at elevated temperature‐pressure conditions (120 °C/180 °C, 18 MPa), considering the effects of extra calcite addition and the initial concentration of Ca2+ in solution. During reactions, the changes in water chemistry and mineral surface morphology are monitored through effluent sampling and scanning electron microscope (SEM) observation, respectively and they are further analyzed in PHREEQC by the method of mineral saturation index. It is found that the simultaneous dissolution of chlorite and calcite in CO2 saturated solutions will lead to a competition for H+, and the formation of massive surface complex CaHCO3– by Ca2+ in the initial solutions will lead to the consumption of H+. These inhibit the proton‐promoted dissolution of chlorite. But when the concentration of Ca2+ is increased to meet the requirements for ankerite precipitation, the demand of ankerite precipitation for elements Fe and Mg will conversely promote the chlorite dissolution. Besides, the concentration of Ca2+ required for the precipitation of ankerite is relatively low, which implies that the injected CO2 can be mineralized and trapped by the chlorite dissolution process easily. © 2022 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Geological carbon sequestration mitigates climate change by capturing and storing carbon dioxide (CO2) emissions in deep geologic formations. Dissolution trapping is one mechanism by which CO2 can be trapped in a deep formation. However, heterogeneity can significantly affect the dissolution efficiency. This work addresses the injection of CO2 in perfectly stratified saline formations under uncertainty. Monte Carlo two‐phase flow compositional simulations involving the dissolution of CO2 into brine and evaporation of water into the CO2‐rich phase are presented. We systematically analyzed the interplay between heterogeneity σY2 $\left({\sigma }_{Y}^{2}\right)$ and gravity factor (G), which is shown to control the migration of the CO2 plume as well as the temporal evolution of dissolution efficiency. Results show that when G is important, vertical segregation controls the overall behavior of CO2, diminishing the influence of small‐scale heterogeneity on dissolution. However, when G is relatively small compared to σY2 ${\sigma }_{Y}^{2}$, CO2 migrates preferentially through high permeability layers and dissolution efficiency increases with σY2 ${\sigma }_{Y}^{2}$ due to the stretching of the CO2 plume that enhances mixing. As a result, in this situation, the upscaling of permeability leads to an underestimation of the dissolution efficiency. A review of field sites shows that dissolution is heterogeneity‐controlled in most real systems. Knowing that most numerical models cannot afford to represent heterogeneity at an adequate scale, results indicate that dissolution efficiency can be typically underestimated by a factor close to 1.5. Key Points: Mont Carlo simulations of geological carbon sequestration (GCS) in randomly stratified porous mediaIn heterogeneity‐controlled systems, permeability stratification enhances CO2 dissolution efficiency by stretching the interface between gas and brine phasesThe upscaling of permeability can lead to an underestimation of the dissolution efficiency [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]

Tropical dry forests experience pronounced seasonal changes in precipitation manifested in varied plant phenologies. At landscape scales, geologic substrate—one of the least understood abiotic factors interacting with precipitation—may modulate phenological responses in these forests through a combination of mechanisms regulating water and nutrient use. We leveraged a phenological dataset from the semiarid island of Curaçao to examine the extent to which plant phenology at multiple levels of biological organization diverge under different geologies. Monthly observations over a 30‐month period of leaves, flowers, and fruits of 69 plant species of different life forms at three nearby sites differing in their underlaying geology were used to examine intra‐ and inter‐annual plant responses at species, community, and system levels. The integration of leaf, flower, and fruit observations at intra‐annual scales revealed diverse phenological strategies among species, broad associations with geologic substrate, and the extent of intra‐specific variation as a function of geology. The community‐ and system‐level analyses at inter‐annual scales showed a reduction in mean leaf scores during the 30‐month period, a weak and strong leafless period in 1993 and 1994, respectively, and differences among geologic substrates. Finally, we observed significant and positive relationships between precipitation and the phenophase scores; the strength of the relationships varied with phenophase and geologic substrate. Results of this work emphasize the importance of geologic substrate, and more broadly speaking landscape heterogeneity, in modulating plant phenological responses in tropical dry forests. Ultimately, this information will become important to understand and mitigate global climate change impacts. Abstract in Spanish is available with online material. [ABSTRACT FROM AUTHOR]

EPA and States share program implementation in 7 States and EPA directly implements the entire UIC program in 10 States (US EPA 2015). If injection into a USDW for waste fluid disposal is absolutely necessary, treatment of the waste fluid should be strongly considered. The Environmental Protection Agency (EPA) regulates the injection of industrial fluids into geologic formations through the underground injection control (UIC) program authorized by Section 1421 of the 1974 Safe Drinking Water Act (SDWA). Subsurface injection of industrial fluids has been common practice in the United States for the past 50 years and is utilized primarily for disposal of waste fluids and enhanced recovery of oil and gas. [Extracted from the article]

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]

Aquifer remediation with in‐situ soil washing techniques and enhanced oil removal typically involves the injection of liquid solutions into the geological formation to displace and mobilize non‐aqueous phase liquids (NAPLs). The efficiency of these systems is oftentimes low because the displacing fluid bypasses large quantities of NAPL due to the inherent complexity of a heterogeneous natural system. Here, engineered injection and extraction (EIE) generated by rotating periodic injection is proposed as a method to enhance NAPL removal and mixing. To evaluate the method, we perform two‐phase flow simulations in multiple realizations of random permeability fields with different correlation structures and connectivity between injection and extraction wells embedded in a five‐spot pattern. Results show that EIE can significantly improve removal efficiency and mixing depending on several controlling factors. The effects of EIE are more significant under unfavorable conditions, that is, when injection and extraction wells are well‐connected through preferential channels, permeabilities are highly heterogeneous, and/or the mobility ratio between the wetting and the non‐wetting fluids is larger than one. Removal efficiency reaches its maximum value when the Kubo number is close to one, that is, when the saturation front travels one range of the permeability field in an injection pulse. These effects can develop in just a few cycles. However, removal efficiency should undergo first an early stage with detrimental effects in order to maximize removal in the long term. EIE not only enhances NAPL removal and mixing but also reduces the uncertainty, making the system more reliable and less dependent on heterogeneity. Key Points: Engineered injection and extraction enhances non‐aqueous phase liquids removal and mixing in heterogeneous porous media while reducing uncertaintyRemoval efficiency increases to a maximum value when the injection pulse satisfies that the Kubo number is close to oneThe relative benefit of chaotic advection is substantially larger in conditions of unfavorable aquifer heterogeneity and connectivity [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]

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]

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]

Monitoring brine leakage from CO2 geological storages (CGS) is necessary to protect shallow aquifers against contamination. A framework for designing CGS monitoring systems that optimally use both easily available shallow zone data and hard‐to‐obtain deep zone observations is developed and validated. This framework is based on calibrating a transport model using monitoring data to determine leakage source conditions and then predict the subsequent brine plume that potentially contaminates shallow aquifers. As cost considerations are expected to limit monitoring deep formations, the framework is developed to minimize the number of deep observation points (e.g., deep sensors). The best monitoring locations that yield the most worthful data for reducing predictive uncertainty is selected by integrating linear uncertainty analysis with Genetic Algorithm under this framework. Due to practical challenges, testing such a framework in the field is not feasible. Thus, the framework was tested in an intermediate‐scale soil tank, where monitoring data on brine leakage plume development from the storage zone to the shallow aquifer were collected. Predictions made by a transport model calibrated on these data were then compared with experimental measurements to evaluate data informativity and thus validate the framework's applicability. The results demonstrate the framework ability to select the optimum monitoring locations for leakage detection and model calibration. It was also found that not only deep observations, but also shallow zone data are worthful to determine source conditions. Moreover, the results showed the possibility of identifying the likely areas to be impacted in the shallow aquifer using early stage monitoring data. Plain Language Summary: Potential exists for formation brine to leak through caprock discontinuities when CO2 is injected into deep geologic formations to reduce greenhouse gas loading to the atmosphere. Strategies are needed to evaluate storage permanence and protect shallow groundwater from contamination using monitoring systems. As installing the necessary sensors in deep zones is expensive, cost reduction should be a goal in designing such monitoring systems. This research validated an optimal design framework that integrates observations from shallow wells with a limited number of deep sensors based on the value of collected data in meeting monitoring goals. As field validation of such a framework is not technically feasible, data from a simulated leakage event in a large laboratory test tank was used. In this validation, data collected from the monitoring locations selected by the framework was used to calibrate a transport model. The validation results showed how model predictions of leakage rate and location, lateral flow in the storage zone, and plume development in the shallow aquifer were improved by calibrating the model with the collected monitoring data. Key Points: Linear uncertainty analysis combined with Genetic Algorithm is used to design monitoring systems for brine leakage from CO2 storagesExperimental data generated in an intermediate‐scale test system simulating brine leakage was used to validate the developed frameworkThe results show that the prediction accuracy of the brine plume varies largely with the worth of data used in model calibration [ABSTRACT FROM AUTHOR]

Density‐driven dissolution of carbon dioxide in water is a well‐known and much described mechanism in geological sequestration of this greenhouse gas. It is remarkable that such enhanced dissolution does not receive attention in karst hydrology and speleology. Models and hypotheses on karst development are complex and consider many different processes. We focus here on the influence of CO2 partial gas pressures at the interface between atmosphere and karst water on the dynamics of dissolved CO2 concentrations below the water table. Seasonal variations of microbial soil activity and root respiration or barometric‐pressure changes cause fluctuations in CO2 partial pressures. Dependent on the existence and strength of a karst‐water background flow, fingering regimes might be triggered causing enhanced dissolution of CO2. This allows replenishment of CO2, and, thus, dissolutional power even deep in the water body without the need for percolating water to transport dissolved CO2. We present and discuss simplified and generic experimental and computational scenarios to strengthen our claim, and we try to give answers to: how much? and under which circumstances? The applied numerical model solves the Navier‐Stokes equation with water density dependent on CO2 concentration and temperature. We show that calculated CO2 mass fluxes into the water bodies are dependent on the ratio of Péclet to Rayleigh numbers (Pe/Ra) and show a local minimum around Pe/Ra = 1, i.e. when natural and forced convection are about equal. Concluding, we claim that there is sufficient reason to consider density‐driven dissolution as a process of relevance in karstification if circumstances are given. Plain Language Summary: Karst systems form in rocks, such as limestones, that are soluble in the presence of water charged with carbonic acid. The carbon dioxide (CO2) can take different pathways to replenish dissolutional power in karst water. This study discusses a pathway that did not receive much attention yet. The density of water increases when CO2 dissolves, and, when dissolution occurs at the water table, instabilities may be induced. This can trigger fingering‐like flow and enhance the rate of dissolution at the water table. The phenomenon is well‐known as a major trapping mechanism for CO2 injected into geological formations for mitigating greenhouse‐gas emissions. The more so is it remarkable that the same phenomenon is not discussed in karst hydrology and speleology. Of course, the different conditions of concentrations, pressures, and temperatures require attention. For realistic conditions, we demonstrate experimentally and by numerical simulations that density‐induced transport of CO2 is significant. The lab experiment used a 6 m long vertical column and imitates an analog to a cave lake. We can see that within a few months time, significant amounts of CO2 can be dissolved at karst‐typical elevated gaseous CO2 concentrations. The influence of natural ground‐/karst water background flow is addressed by numerical simulations. Key Points: Density‐driven CO2 dissolution is a process that deserves more attention in karstification theories and beyondFluctuating CO2 partial pressures in the vadose zone can enhance dissolution of CO2 in phreatic karst waterGeneric scenarios are used to demonstrate how density‐driven dissolution can contribute to replenishing CO2 in karst water [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]

The Paris Agreement established global ambitious targets for reducing carbon dioxide (CO2) emissions, requiring the rapid and extensive development of low carbon technologies, and one of the most efficient is CO2 geological storage. Among the deep geological formations used for CO2 storage, the shale layers have been a new emerging field with higher efficiency because they are abundant and have a high content of organic matter that is favorable for CO2 retention. However, one of the challenges in evaluating a location for potentials reservoirs is the adequate geological characterization and storage volume estimation. The study evaluates the Irati Formation of the Paraná Basin based on wireline logs information within Southeastern Brazil, where most stationary sources of carbon emissions are located. Three‐dimensional (3D) implicit modeling techniques were applied not only for volume calculation purpose, but also in the site selection stage, generating thematic 3D models indicating thickness, depth, structures, and distance to aquifer systems. The limestones, shales, and black shales of the Irati Formation were locally grouped into six units considering the geological composition and spatial continuity. Based on the 3D model and reservoir parameters, the organic‐rich shale Unit E with a theoretical capacity of 1.85 Gt is considerable for CO2 storage. The estimated CO2 storage capacity is promising because it is higher than the total CO2 locally produced, and it could support the implantation of new projects in this region. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Heterogeneity and insufficient site characterization limit our knowledge of the subsurface. Inversion techniques, which minimize the mismatch between observations and model predictions, have become an essential tool of subsurface characterization. Most optimization‐based approaches fail to incorporate various implicit priors and capture the geological complexity. We overcome these limitations by deploying the plug‐and‐play and consensus equilibrium (CE) strategies, which provide a flexible framework for image reconstruction. Our CE methodology for spatial delineation of geologic formations consists of an image denoiser and a variational auto‐encoder (deep learning‐based emulator). The former ameliorates the reconstruction noise, yielding well‐defined geological structures; its mathematical equivalence with the proximal operator allows the deployment of advanced denoisers (e.g., CNN‐based denoiser) that do not correspond to a regularization objective. The latter defines a geology prior that imposes a geological constraint, for example, continuity and shape of geological features, onto the reconstructed image. We conduct a series of numerical experiments dealing with transient two‐dimensional flow driven by a pumping well and natural hydraulic head gradient. They demonstrate the CE framework's ability to delineate, both probabilistically and deterministically, complex subsurface environments with sufficient quality. Key Points: We developed consensus equilibrium framework to reconstruct the subsurface from sparse dataOur framework integrates conventional optimization methods with machine learning‐based methodsThe method accurately reconstructs geologically complex models and efficiently reduces and quantifies the posterior uncertainty [ABSTRACT FROM AUTHOR]

Eocene strata of the Elko Formation record lacustrine deposition within the Nevada hinterland of the North American Cordillera. We present a detailed geochemical stratigraphy enabled by high‐sampling‐resolution geochronology from lacus trine limestone and interbedded volcanic rocks of the Elko Formation. Two intervals of lacustrine deposition, an early Eocene "Lake Adobe" of limited aerial extent and a laterally extensive middle Eocene "Lake Elko," are separated by ∼5 m.y. of apparent unconformity. Sediments deposited in the apparently short‐lived (49.5–48.5 Ma) early Eocene Lake Adobe exhibit high‐amplitude covariation of δ18O, δ13C and 87Sr/86Sr, which suggests a dynamically changing catchment and precipitation regime. Lake Elko formed during the middle Eocene, and its strata record three geochemically distinct phases, indicating it was a single interconnected water body that became increasingly evaporative over time. The lower Elko Formation (44.0–42.5 Ma) was deposited in a freshwater lake. Middle Elko Formation (42.5–41.2 Ma) lithofacies and geochemistry suggest that an increasingly saline and alkaline Lake Elko experienced salinity stratification‐induced hypolimnion disoxia and burial of 12C‐rich organic matter. The upper Elko Formation (41.2–40.5 Ma) records a shallow final phase of Lake Elko that experienced short residence times and a breakdown in stratification. A sharp decline of 87Sr/86Sr in the upper Elko Formation reflects an increasing aerial extent of low‐87Sr/86Sr volcanic deposits from nearby calderas. Middle Eocene strata record ponding of paleodrainage, increasing hydrologic isolation and volcanism, consistent with progressive north to south removal of the Farallon flat slab and/or delamination of the lower lithospheric mantle of the North American plate. Plain Language Summary: Large lakes formed in the region that is now northeast Nevada between 50 and 40 million years ago. This region was at high elevation and undergoing a transition from compressional to extensional plate tectonic forces at that time. The geologic record shows that lakes formation started locally at 49.5 million years ago with a short‐lived freshwater Lake Adobe. Later, approximately 43.5 million years ago, a broad Lake Elko formed and then became increasingly evaporative over the next 3 million years, likely due to removal of the shallowly subducting Farallon slab from beneath the region. Key Points: Lakes formed in the hinterland of the North American Cordillera during the Eocene during a transition from contraction to extensionLake Elko expanded and became increasingly evaporative across 3.5 Ma from 43.5–40.5 Ma, coincident with an episode of explosive siliceous magmatismLake formation and drainage isolation likely records the progressive removal of the flattened Farallon slab from beneath the Cordillera [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]

Carbon capture and storage has been considered as a realistic approach to reducing atmospheric CO2 concentrations. However, the cost of capturing high‐purity CO2 typically used for geological storage (e.g., 98%) is high. Direct air capture (DAC), a technology that extracts CO2 of relatively low‐purity from the ambient atmosphere, has been recently proposed as a means to achieve negative CO2 emissions when the product is sequestered underground. Although the CO2 produced by DAC is of low‐purity, the other gaseous components (mainly nitrogen and oxygen) are not hazardous materials like NOx and SOx that must be typically dealt with by conventional projects in coal‐burning plants. Here, we evaluate geological storage of the low‐purity CO2 captured via advanced membrane‐based DAC technology. The ubiquity of ambient air is important in reducing transport costs and ensuring social acceptance as the CO2 product can be both produced and stored at sites in remote areas, such as deserts and offshore platforms. We calculated the density of CO2–N2–O2 mixtures via molecular dynamics simulation and evaluated the cost of the low‐purity CO2 storage. Our evaluation suggests that the storage of low‐purity CO2 in geological formations is environmentally acceptable and economically viable. © 2021 The Authors. Greenhouse Gases: Science and Technology published by Society of Chemical Industry and John Wiley & Sons Ltd. [ABSTRACT FROM AUTHOR]

Crater morphology and surface age of asteroid (162173) Ryugu are characterized using the high‐resolution images obtained by the Hayabusa2 spacecraft. Our observations reveal that the abundant boulders on and under the surface of the rubble‐pile asteroid affect crater morphology. Most of the craters on Ryugu exhibit well‐defined circular depressions, unlike those observed on asteroid Itokawa. The craters are typically outlined by boulders remaining on the rim. Large craters (diameter > 100 m) host abundant and sometimes unproportionally large boulders on their floors. Small craters (<20 m) are characterized by smooth circular floors distinguishable from the boulder‐rich exterior. Such small craters tend to have dark centers of unclear origin. The correlation between crater size and boulder number density suggests that some processes sort the size of boulders in the shallow (<30 m) subsurface. Furthermore, the crater size‐frequency distributions (CSFDs) of different regions on Ryugu record multiple geologic events, revealing the diverse geologic history on this 1‐km asteroid. Our crater‐counting analyses indicate that the equatorial ridge is the oldest structure of Ryugu and was formed 23–30 Myr ago. Then, Ryugu was partially resurfaced, possibly by the impact that formed the Urashima crater 5–12 Myr ago. Subsequently, a large‐scale resurfacing event formed the western bulge and the fossae 2–9 Myr ago. Following this process, the spin of Ryugu slowed down plausibly due to the YORP effect. The transition of isochrons in a CSFD suggests that Ryugu was decoupled from the main belt and transferred to a near‐Earth orbit 0.2–7 Myr ago. Plain Language Summary: Japan's asteroid explorer Hayabusa2 visited the carbon‐rich, 1‐km asteroid named Ryugu. One of the onboard cameras took many pictures of asteroid's surface. In order to know the history of this asteroid, we estimate the age of different geologic units by counting craters. We also documented how the craters on this asteroid look, to help understand the geology of the carbon‐rich world. We found that the mountain range running along the equator formed 23‐30 million years ago. About 5–12 million years ago, the meteorite impact that formed the biggest crater on this asteroid likely scattered soil around, erasing nearby craters that existed before. Then, about 2–9 million years ago, the western half of this asteroid was wiped out by a large‐scale movement of rocks and pebbles that build this asteroid, because the asteroid was spinning fast and unstable at that time. Then, sometime between 0.2 and 7 million years ago, this asteroid left the home of asteroids located between Mars and Jupiter orbits, and came to the orbit passing near the Earth. During its journey to the near‐Earth orbit, the spin of the asteroid slowed down because of the very weak but effective force by heat radiation from surface rocks. Key Points: Craters on asteroid Ryugu are documented and counted based on the high‐resolution images obtained with Hayabusa2's telescopic cameraCrater morphology on Ryugu ranges from distinct >100‐m circular depressions to <10 m smooth texture outlined by bouldersCrater chronology reveals multiple resurfacing events on each hemisphere 2–12 Myr ago and Ryugu's departure from the main belt <7 Myr ago [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]

Leakage from geologic CO2 sequestration (GCS) reservoirs to overlying underground sources of drinking water (USDW) is a tangible risk. This study is an integrated assessment that combines column experiments and reactive transport simulations of sediments sampled from the Ogallala aquifer above an active commercial‐scale GCS site (the Farnsworth Unit in northern Texas). Experimental and simulation results suggest that carbonate mineral (calcite and dolomite) dissolution is the most significant reaction following CO2 intrusion, and is also the dominant source of trace metal release. Cation exchange is another key mechanism controlling trace metal release by cation interference. Most of the trace metals, including Ba, Sr, As, Pb, and Zn, show a short‐term release and quickly drop to the baseline values, suggesting low risk to the overlying USDW quality. Other trace metals, such as Mn and U, exhibit a tangible increase of their concentrations in the beginning, and drop to a higher level compared to the baseline, which may become a potential concern of long‐term USDW quality change with CO2 introduction. This study provides a comprehensive example of combining laboratory experiments and simulations for assessment of CO2‐sediment interactions with combined release mechanisms in shallow groundwater aquifers. Data presented here provides useful insights for quantitative risk assessment and effective public education regarding CO2 geological sequestration, and trace metal reactive transport studies in shallow groundwater aquifers. Plain Language Summary: Geologic CO2 sequestration (GCS) is an applicable option for reducing greenhouse gas emissions from point sources by injecting CO2 into deep geologic formations. The key concern of GCS is the potential leakage into shallow groundwater aquifers, because CO2 may cause water pH reduction and metal release from sediments. To study CO2‐water‐sediment interactions and potential metal release mechanisms from the sediments, this study combines laboratory column experiments and reactive transport simulations of shallow groundwater aquifer sand samples above an active GCS site. Results of experiments and simulations suggest that dissolution of carbonate minerals is the most significant reaction in CO2‐rich conditions, leading to metal release into aqueous phase. Cation exchange is another mechanism controlling metal release. Most of the toxic trace metals show a short‐term release and quickly drop to a lower value, suggesting low risk to groundwater quality. Metals such as manganese (Mn) and uranium (U) show a stable release with high CO2 level, suggesting a possible risk of drinkable groundwater quality with CO2 leakage. This study provides useful information for risk assessment and effective public education for GCS, as well as reactive transport research of trace metals in shallow groundwater aquifers. Key Points: CO2‐water‐sediment interactions in the largest aquifer in the USA is assessed by combined column experiments and numerical simulationsCarbonate mineral impurity and cation exchange are key mechanisms of cation release in CO2‐rich conditionsManganese and uranium exhibit a stable release during the experiments, which might impact groundwater quality with CO2 intrusion [ABSTRACT FROM AUTHOR]