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Erosional scars, slumps, slides and debrites (mass-transport deposits) on submarine slopes form relief that influences turbidity current behaviour. However, the interaction of mass-transport deposit emplacement kinematics (i.e. rapid emplacement versus creep), the morphology of the evolving seafloor topography and subsequent flow types is complicated. This study describes two outcrop examples of deep-water, predominantly turbiditic, deposits overlying mass-transport deposits, from the Eocene slope succession of the Aínsa Basin (Spanish Pyrenees). In both examples, the mass-transport deposit substrate continued to creep contemporaneously with turbidity current deposition and bypass. In the first case study, structures in the mass-transport deposits are extensional and oriented parallel to flow. In the second, structures are compressional and oriented perpendicular to flow. Mudstones dominate the slope succession, but deposits overlying mass-transport deposits form sandstone-prone accumulations. Lateral confinement by flow-parallel extensional faults enhanced channel-formation. Channel incision occurred close to the exhumed fault plane on the hangingwall. Incision ceased as the fault gradually locked-up, and channels avulsed to the hangingwall of a newly active normal fault, while the abandoned channel was filled by a thinning and fining-upward succession. Barriers formed where the long axes of compressional anticlines developed in mass-transport deposits formed perpendicular to flow. Here, turbidites filled the bathymetric lows in the axes of synclines. Continued tightening of synclinal depocentres led to repeated stoss side trapping and upslope accretion of coarse-grained sediment accumulation. This generated thickening and coarsening-up, followed by thinning and fining-upward successions, tracking the decreasing, then increasing flow bypass associated with topographic expression on the mass-transport deposit. This study shows how post-emplacement creep, and orientation of topographic features on mass-transport deposits, influence the routing and deposition of contemporaneous turbidity currents, and illustrates examples of facies successions that could be misinterpreted as the product of other autogenic submarine slope processes, such as lateral migration of sinuous channels, or compensational lobe stacking.

Swelling of shale in response to interaction with water is an important consideration within subsurface energy systems. In the case of waste disposal, swelling can provide important barriers around the waste and enhance the sealing ability of rocks. For shale gas exploration purpose, however, swelling may cause wellbore instability. Therefore, a careful study of shale swelling is critical for subsurface energy related applications. Here, the swelling effects of shale were imaged at nanoscale using an advanced synchrotron Transmission X-ray Microscopy (TXM) imaging technique for the first time, with a spatial resolution down to 40.9 nm. Organic matter and clays within the analysed sample were observed to display large swelling effects which resulted in a 50% reduction in porosity. Strain maps generated using Digital Volume Correlation (DVC) show deformation and significant strain were mostly localized to between the contact boundaries of sharp brittle minerals and softer organic matter and clays. This is the first study, to our knowledge, to directly image the swelling deformation of shale at the tens of nanometer scale and provide local information on the strain evolution.

Determination of mineral texture and diagenetic features in mudstones is crucial to reveal the history of their pore systems and provides key information to predict their future sealing ability, reactivity and storage capacity for sequestered CO 2, hydrogen storage or nuclear waste disposal. To understand the spatial transport and storage of fluids, it is necessary to map the distribution of minerals and fractures in three dimensions (3D). This study proposes a novel, multi-scale three-dimensional (3D) imaging method, i.e., a combination of synchrotron- sourced micro- x-ray tomography and lab- sourced nano-tomography, to investigate the sedimentology and diagenetic features of the Bowland Shale, one of the most volumetrically important mudstone-dominated systems in the UK. Diagenetic minerals have been identified and characterised, including pyrite, calcite, kaolinite, illite, chlorite, dolomite, ankerite and authigenic quartz (micro-sized quartz and quartz overgrowths). Multi-scale 3D images provide detailed information about dolomite-ankerite zonation and carbonate dissolution pores. These features cannot be observed or quantified by conventional 2D methods, and they have not been reported in this subject area before. Using these results, potential reactions during carbon storage and other subsurface storage applications are predicted.

Mud dominates volumetrically the fraction of sediment delivered and deposited in deep-water environments, and mudstone is a major component of basin-floor successions. However, studies of basin-floor deposits have mainly focused on their proximal sandstone-prone part. A consequent bias therefore remains in the understanding of depositional processes and stratigraphic architecture in mudstone-prone distal settings beyond the sandstone pinchouts of basin-floor fans. This study uses macroscopic and microscopic descriptions of over 500 m of continuous cores from research boreholes from the Permian Skoorsteenberg Formation of the Karoo Basin, South Africa, to document the sedimentology, stratigraphy, and ichnology of a distal mudstone-prone basin-floor succession. Very thin- to thin-bedded mudstones, deposited by low-density turbidity currents, stack to form bedsets bounded by thin packages (< 0.7 m thick) of background mudstones. Genetically related bedsets stack to form bedset packages, which are bounded by thicker (> 0.7 m thick) background mudstones. Stratigraphic correlation between cores suggests that bedsets represent the distal fringes of submarine fan lobe elements and/or lobes, and bedset packages represent the distal fringes of lobe complexes and/or lobe complex sets. The internal stacking pattern of bedsets and bedset packages is highly variable vertically and laterally, which records dominantly autogenic processes (e.g., compensational stacking, avulsion of feeder channels). The background mudstones are characterized by remnant tractional structures and outsize particles, and are interpreted as deposited from low-density turbidity currents and debris flows before intense biogenic reworking. These observations challenge the idea that mud accumulates only from hemipelagic suspension fallout in distal basin-floor environments. Thin background mudstones separating bedsets (< 0.7 m thick) are interpreted to mainly represent autogenically driven lobe abandonment due to up-dip channel avulsion. The thicker background mudstones separating bedset packages (> 0.7 m thick) are interpreted to dominantly mark allogenically driven regional decrease of sand supply to the basin floor. The recognition of sandstone-prone basin-floor fans passing into genetically linked distal fringe mudstones suggests that submarine lobes are at least ∼ 20 km longer than previously estimated. This study provides sedimentological, stratigraphic, and ichnological criteria to differentiate mudstones deposited in different sub-environments in distal deep-water basin-floor settings, with implications for the accurate characterization of basin-floor fan architecture, and their use as archives of paleoenvironmental change.

Purpose The proportion of people living in urbanised areas is predicted to rise to > 65% by 2050, and therefore, more humans than ever will be exposed to urban environmental pollution. Accumulation of organic and inorganic substances on street and road surfaces is a major global challenge requiring scientifically robust methods of establishing risk that inform management strategies. This aim of this contribution is to critically review the global literature on urban road–deposited sediment contamination with a specific focus on variability in sampling and analytical methods. Materials and methods In order to assess the concentration of contaminants in global road-deposited sediment (RDS), a comprehensive search of published RDS studies was completed. We review methodological approaches used in RDS studies to highlight the variability in datasets as a result of sampling technique, grain size fractionation, geochemical and mineralogical characterisation methods and establishing the influence of local geology on contaminant concentrations. We also consider emerging contaminants in RDS, and we provide a workflow diagram which promotes a standardised sampling and analysis regime that we believe can reduce data variability and promote collaboration when it comes to tackling the important issue of RDS contamination. Results and discussion Across the literature, Asia (except China) and Africa are underrepresented in RDS studies despite these continents having the largest and fastest growing populations, respectively. The removal of tetraethyl lead from gasoline produced a noticeable decrease in lead concentrations in global RDS, and platinum group element (PGE) concentrations in RDS were consistent with catalytic converter usage. Research into the impact of electric vehicles on non-exhaust emissions suggests other contaminants such as zinc may become more prominent in the future. Most RDS studies consider grain size fractions larger than > 20 μm due to sampling constraints despite RDS Conclusions This review highlights considerable variability in sampling and analytical approach which makes it difficult to identify broad global patterns in RDS contamination. To remove this variability from future RDS research, this review suggests a workflow plan which attempts to improve the comparability between RDS studies. Such comparability is crucial in identifying more discrete RDS trends and informing future emission policy.

The composition and characteristics of organic matter within shales can reveal important information on hydrocarbon generation, migration and accumulation processes during catagenesis. It may also impact upon the chemical properties and mechanical behavior of shales acting as hydrocarbon reservoirs or caprocks/seals for carbon and subsurface energy storage. Here we apply advanced atomic force microscopy-based infrared spectroscopy (AFM-IR) to capture the in-situ chemical structure of nanoscale molecular composition of individual organic particles and map the distribution of typical functional groups nondestructively; something that cannot be achieved via conventional analysis since some methods damage the sample, some only collect bulk measurements and some do not achieve nano-scale resolution. The nanoscale geochemical characteristics of organic matter in thermally mature samples of a Baltic Basin shale, from Lithuania and the Bowland Shale, from the UK, obtained from AFM-IR, are compared in this study. Significant chemical heterogeneity can be observed in migrated solid bitumen. In contrast, graptolite, alginite and inertinite generally display homogeneous molecular composition. The potential role of laminae as barriers to the vertical migration of hydrocarbons is also apparent. This research provides insights into nanoscale geochemical information on different organic matter types in thermally-mature shales to enhance the understanding of molecular structure transformation of organic matter during hydrocarbon expulsion and migration processes, and also sheds light on implications of nanogeochemistry for enhanced gas recovery, carbon sequestration and underground hydrogen storage-related energy applications. We also characterised specific materials which have not been reported in other geological studies using AFM-IR. Some of them display similar characteristics to other organic matter particles in the samples, but the possibilities of unknown organic contaminants introduced to the sample during sample storage or preparation stages cannot be ruled out. A comprehensive analysis on this undefined organic material is provided. Standardized approaches during sample preparation and storage are required for future research to dislodge potential surface-attached contaminants.

Due to the complexity of sedimentary rocks, especially the fine-grained and highly-heterogeneous nature of some argillaceous caprocks in the subsurface, it is challenging to directly characterise the macroscale changes during CO 2 storage. The investigation of microstructural changes in CO 2-fluid-rock reactions helps provide a fundamental understanding of macroscopic properties as the microstructure constrains their hydraulic, mechanical and geochemical behaviour. Because of distinct petrophysical properties, the effect of geochemical reaction on caprocks and reservoir rocks is dramatically different. In order to provide a comprehensive knowledge of microstructural changes induced by geochemical reactions and facilitate the application to large scale carbon storage research, this review summarizes representative laboratory measurements conducted on typical caprocks (e.g. mudstone and evaporite) and reservoir rocks (e.g. sandstone and carbonates). Key findings include: (1) Water can generally facilitate CO 2-rock reactions. The effect of dissolution and precipitation on the pore structure largely depends on the inherent heterogeneity of rock (including primary structure, mineralogy, thermal maturity), and the environmental conditions (temperature, pressure, fluid). (2) Adsorption-induced swelling of clay minerals and organic matter in mudstone may increase or reduce the pore space, which is primarily controlled by the treatment pressure of CO 2 within the same caprock system. (3) Fines migration and the re-precipitation of minerals are the major factors causing pore throat blockage of sandstone during CO 2 flooding. (4) Highly conductive wormholes formed in carbonates during CO 2 percolation can significantly enhance fluid injectivity, whereas a long-term thermodynamic equilibrium in the subsurface tends to counteract the increase in porosity due to the healing mechanism of mineral precipitation. Further, how to link laboratory work with modelling to realise large-scale and temporal-scale prediction are summarised. Finally, promising developments and research directions are proposed.

Mineral authigenesis in mudstones responds differently across the compositional spectrum of fine-grained rocks, resulting in a complex array of possible rock fabrics that affect the mechanical capacity of mudstones. Within carbonate-rich mudstones, geochemical controls on silicate and carbonate mineral reactions are variable and poorly understood. Here we analyse the diagenetic minerals of the carbonate-rich Hodder Mudstone from the Carboniferous Bowland Basin, UK, using SEM petrography combined with X-ray-based inorganic geochemical data. Our findings show that up to 90% of quartz cements in the samples are diagenetic, originating mainly from biogenic silica dissolution and clay mineral reactions. It is also evident that due to the varying diagenetic silica-yielding reactions, authigenic silica overgrowths and isolated authigenic quartz crystals are localized in argillaceous samples, while calcareous samples are characterized by silica replacement textures and quartz/calcite intergrowths. Moreover, euhedral dolomite crystals are concentrated within argillaceous units, whereas calcareous units are characterized by anhedral dolomite precipitation and replacement textures. These finding presents a case for facies-selective cementation, as both early and burial diagenetic alterations were observed to be controlled by primary depositional components of biogenic debris and extrabasinal silicate detritus that resulted in complex and variable precipitation of authigenic minerals.

Microstructures and pore systems in shales are key to understanding the role of shale in many energy applications. This study proposes a novel multi-stage upscaling procedure to comprehensively investigate the heterogeneous and complex microstructures and pore systems in a laminated and microfractured shale, utilizing 3D multi-scale imaging data. Five imaging techniques were used for characterisation from sub-nanoscale to macroscale (core-scale), spanning four orders of magnitude. Image data collected using X-ray tomography, Focused Ion Beam, and Electron Tomography techniques range in voxel size from 0.6 nm to 13 μm.Prior to upscaling, a novel two-step analysis was performed to ensure sub-samples were representative. Following this, a three-step procedure, based on homogenising descriptors and computed volume coefficients, was used to upscale the quantified microstructure and pore system. At the highest resolution (nanoscale), four distinct pore types were identified. At the sub-micron scale equations were derived for three pore-associated phases. At the microscale, the volume coefficients were recalculated to upscale the pore system to the macroscale (millimetre). The accuracy of the upscaling methodology was verified, predicting the total porosity within 7.2% discrepancy. The results provide a unique perspective to understand heterogeneous rock types, breaking though prior scale limitations in the pore system.

Deep-water mudstones are often considered as background sediments, deposited by vertical suspension fallout, and the range of transport and depositional processes are poorly understood compared to their shallow-marine counterparts. Here, we present a dataset from a 538.50 m-thick coredsuccession through the Permian muddy lower Ecca Group of the Tanqua depocentre (southwest Karoo Basin, South Africa). This study aims to characterize the range of mudstone facies, transport and depositional processes, and stacking patterns recorded in deep-water environments prior to deposition of the Tanqua Karoo sandy basin-floor fans. A combination of macroscopic and microscopic description techniques and ichnological analysis has defined nine sedimentary facies that stack in a repeated pattern to produce 2–26-m-thick depositional units. The lower part of each unit is characterized by bedded mudstone deposited by dilute, low-density turbidity currents with evidence for hyperpycnal-flowprocesses and sediment remobilization. The upper part of each unit is dominated by more organic-rich bedded mudstone with common mudstone intraclasts, deposited by debris flows and transitional flows, with scarce indicators of suspension fallout. The intensity of bioturbation and burrow size increases upward through each depositional unit, consistent with a decrease in physicochemically stressed conditions, linked to a lower sediment accumulation rate. This vertical facies transition in the single well dataset can be interpreted to represent relative sea level variations, where the hyperpycnal stressed conditions in the lower part of the units were driven by sea level fall and the more bioturbated upper part of the unit represents backstepping, related to sea level rise. Alternatively, this facies transition may represent autogenic compensational stacking. The prevalence of sediment density flow deposits, even in positions distal or lateral to the sediment entry point, challenges the idea that deep-water mudstones are primarily the deposits of passive rainout along continental margins.

This paper quantitatively characterises the microstructure in shales across five scales in 3D, builds a multi-scale model of CH 4 and CO 2 flow pathways and storage, and assesses the potential of enhanced gas recovery and CO 2 storage simultaneously. Injection of CO 2 into shale reservoirs to enhance gas recovery and simultaneously sequester greenhouse gases is a potential contributor towards the carbon-neutral target. It offers a low-carbon, low-cost, low-waste and large-scale solution during the energy transition period. A precondition to efficient gas storage and flow is a sound understanding of how the shale's micro-scale impacts on these phenomena. However, the heterogeneous and complex nature of shales limits the understanding of microstructure and pore systems, making feasibility analysis challenging. This study qualitatively and quantitatively investigates the Bowland shale microstructure in 3D at five length scales: artificial fractures at 10–100 μm scale, matrix fabric at 1–10 μm-scale, individual mineral grains and organic matter particles at 100 nm–1 μm scale, macropores and micro-cracks at 10–100 nm scale and organic matter and mineral pores at 1–10 nm-scale. For each feature, the volume fraction variations along the bedding normal orientation, the fractal dimensions and the degrees of anisotropy were analysed at all corresponding scales for a multi-scale heterogeneity analysis. The results are combined with other bulk laboratory measurements, including supercritical CO 2 and CH 4 adsorption at reservoir conditions, pressure-dependent permeability and nitrogen adsorption pore size distribution, to perform a comprehensive analysis on the storage space and flow pathways. A cross-scale pore size distribution, ranging from 2 nm to 3 μm, was calculated with quantified microstructure. The cumulative porosity is calculated to be 8%. The cumulative surface area is 17.6 m 2 g −1 . A model of CH 4 and CO 2 flow pathways and storage with quantified microstructure is presented and discussed. The feasibility of simultaneously enhanced gas recovery and subsurface CO 2 storage in Bowland shale, the largest shale gas potential formation in the UK, was assessed based using multi-scale microstructure analysis. The potential is estimated to store 19.0–21.2 Gt CO 2 as free molecules, together with 18.3–28.5 Gt CO 2 adsorbed onto pore surfaces, implying a theoretical maximum of 47.5–49.5 Gt carbon storage in the current estimate of 38 trillion cubic metres (∼1300 trillion cubic feet) of Bowland shale. Simple estimates suggest 6.0–15.8 Gt CO 2 may be stored in practice.

The Cenomanian-Turonian Oceanic Anoxic Event (OAE2) is a significant global event that has been linked to major source rock development in marine environments. The aim of this study is to integrate biostratigraphic, sedimentological and geochemical data (including stable carbon isotopes and trace elements) to document the timing and controls of organic matter enrichment across the Cenomanian-Turonian boundary.Morocco has excellent exposures of Tethyan carbonate platform and basinal facies and this paper details a high-resolution analysis of organic-rich Late Cretaceous intervals exposed in the Errachidia-Goulmima Basin, to investigate their relationship to the OAE2. Integrating planktic foraminiferal and ammonite biostratigraphy with carbon isotope correlations indicate that organic-rich black mudstones identified were deposited from latest Cenomanian to early Turonian, suggesting a late-OAE2 to post-OAE2 age.The sedimentology, redox water conditions and palaeoproductivity of the palaeoenvironments were studied to characterise the lithofacies and geochemical signatures, and to analyse the controlling factors for organic–enrichment. In the study area during the lower OAE2 interval, a shallow water mid-ramp environment prevailed, with predominantly bivalve-rich limestone deposition. Subsequent organic-rich mudstone development can be correlated with the latest Cenomanian (late OAE2 interval) and early Turonian (post-OAE interval) transgression, which allowed development of anoxic to euxinic conditions in the outer-ramp environment, characterized by high TOC values, from 2.7 to 17 wt%. Shallow platform locations continued to experience limestone deposition with no organic enrichment.Trace and major element data from the C/T black mudstones show an extremely high concentration in palaeoproductivity-sensitive (P, Zn, Ni and Cu) and redox-sensitive elements (V, Mo, and U). The redox environments evolved from dysoxia to anoxia and sulfidic euxinia, which is interpreted to have provided optimum conditions for organic carbon preservation in the Errachidia area.The results highlight the important interplay of local paleogeography and eustatic sea-level (the late Cenomanian/early Turonian transgressions) as the main controls on organic mudstone deposition, rather than simply global OAE2 control. The development of organic-rich mudstones reflects both increased productivity at this time and enhanced organic matter preservation due to the change in redox bottom water conditions.

Incorporation of reduced inorganic sulfur (S) into organic matter (OM) in euxinic environments is considered a vital route through which OM is preserved for millions of years. However, precipitation of iron sulfides is believed to compete with OM preservation via sulfurisation. High resolution geochemical, petrographic, and electron microprobe (EMPA) analyses were employed to better understand S controls on OM preservation with particular focus on iron sulfides precipitation in organic S-rich mudstones from the Kimmeridge Clay (KCF), Monterey (MF), and Whitby Mudstone [Grey Shale (GS) and Jet Rock (JR) Members] Formations. Analyses indicated that S in the KCF and MF is mostly bound to OM as shown by the relatively high abundance of organic sulfur compounds (OSCs) in their pyrolysates. The relatively low amounts of iron (Fe) in these mudstones permitted extensive reaction of S and OM to occur efficiently, promoting preservation of high amounts OM through sulfurisation. State-of-the-art EMPA imaging of total S and Fe indicated that the S was mainly bound to organics, supporting the geochemical analyses. In contrast, S in the GS and JR was predominantly sequestered as pyrite (FeS2) rather than organically bound, as indicated by the relatively low quantity/absence of OSCs in their pyrolysates, hence, preservation through sulfurisation was less significant in these settings. EMPA imaging of S in these mudstones shows discrete shapes ranging in geometry and size and in most cases correlated with Fe in the corresponding Fe EMPA images, confirming that the S exists in discrete authigenic FeS2. Overall, in line with previous research, this study indicates that preservation of OM through sulfurisation is an important pathway for sequestration of OM. However, an abundance of reactive Fe could hinder this process by preferentially reacting with reduced S, to form iron sulfides (mainly FeS2), thus impeding reactions between OM and S to occur efficiently.

The feasibility and advantages of synchrotron imaging have been demonstrated to effectively characterise fracture initiation and propagation in shales during indentation tests. These include 1) fast (minute-scale) and high-resolution (μm-scale) imaging of fracture initiation, 2) concurrent spatial and temporal information (4D) about fracture development, 3) quantification and modelling of shale deformation prior to fracture. Imaging experiments were performed on four shale samples with different laminations and compositions in different orientations, representative of three key variables in shale microstructure. Fracture initiation and propagation were successfully captured in 3D over time, and strain maps were generated using digital volume correlation (DVC). Subsequently, post-experimental fracture geometries were characterised at nano-scale using complementary SEM imaging. Characterisation results highlight the influence of microstructural and anisotropy variations on the mechanical properties of shales. The fractures tend to kink at the interface of two different textures at both macroscale and microscale due to deformation incompatibility. The average composition appears to provide the major control on hardness and fracture initiation load; while the material texture and the orientation of the indentation to bedding combine to control the fracture propagation direction and geometry. This improved understanding of fracture development in shales is potentially significant in the clean energy applications.

The Bell Island and Wabana groups together comprise a ca. 150-m-thick succession of interbedded clastic andchemical sedimentary rocks composed of eight distinct lithofacies that accumulated along the northern marginof the Rheic Ocean. Lithofacies stacking patterns indicate that deposition occurred during a marine transgressionwith superimposed small-scale sea level fluctuations producing at least six parasequences. Parasequences containingironstone are 10 to 20-m-thick and composed of hummocky cross-stratified sandstone interbeddedwith organic-rich mudstone and phosphatic Fe-silicate-bearing siltstone,which is overlain by hematitic granularironstone capped by an erosive flooding surface.This lithofacies association is interpreted to record the deposition of upwelling-related ironstone on a stormdominatedshelf. The close relationship between Fe-silicates and phosphorite typical of upwelling systemssuggests that Fe was delivered from deep, anoxic, nutrient-rich seawater that also stimulated high surface productivities.The result was the precipitation of authigenic sedimentary apatite in anoxic organic-rich sedimentsthat accumulated near the upwelling front. The gradual advection of Fe-rich waters away from the upwellingfront, initiated precipitation of Fe-silicate coated grains and cements in suboxic pore-waters. Iron pumpedinto shallower environments through advection and Fe-redox cycling is interpreted to have precipitated Fe-(oxyhydr)oxide grains in sediment of the oxygenated middle shelf. These coated grains were subsequentlyconcentrated by fairweather and storm currents on the shoreface to create granular economic Fe deposits.We challenge conventional models of Paleozoic ironstone deposition that rely on a continental source of Fe byproposing a hydrothermal source that supplied Fe2+ to the shelf through upwelling. It also highlights the potentialconnection between the delivery of anoxic, ferruginous seawater to the margins of the Rheic Ocean and theEarly Ordovician extinctions that punctuated the beginning of the Great Ordovician Biodiversification Event.

Atomic force microscopy (AFM) has been widely used in materials science and chemistry research since it was invented in the 1980s. It is a relatively new tool for geosciences and is very powerful for micro- and nano-scale surface characterization with a resolution down to atomic scale. One of the major advantages of this microscopy technique is that it can perform continuous non-destructive measurements on a sample surface. Surface studies provide important structural information for geological materials, especially in energy geosciences. In this review, recent applications of AFM in energy geosciences are critically reviewed, including surface topography, mechanical properties, surface dynamics, and state-of-the-art AFM-based infrared spectroscopy (AFM-IR) and the AFM-Raman technique. AFM imaging enables the mapping and recording of surface information and enhances the understanding of morphology and mechanical properties of geological materials, and is especially useful for those displaying a strong heterogeneity. This review aims to demonstrate the accessibility, versatility, limitations, and promising developments of AFM techniques in energy geoscience. We highlight the major advantages and disadvantages of AFM analysis of geological materials and highlight where factors can cause potential deviations between different experimental results. We further highlight where we believe are the most promising potential uses of AFM. It is foreseen that with the improvement of experimental processes and hardware, AFM will provide indispensable information on surface characterization in a wide range of geological studies.

The development of pore and fracture networks at the nano-scale as a response to heating can reveal coupled physical relationships relevant to several energy applications. A combination of time-lapse 3D imaging and finite-element modelling was performed on two typical thermally immature shale samples, Kimmeridge Clay and Akrabou shale, to investigate thermal response at the nm-scale for the first time. Samples were imaged using Transmission X-ray Microscopy (TXM) with a voxel resolution of 34 nm at the I13–2 beamline at Diamond Light source, UK. Images were taken after heating to temperatures of 20 °C, 300 °C, 350 °C and 400 °C. The initiation of nano-pores within individual minerals and organic matter particles were observed and quantified alongside the evolution from nano-pores to micro-fractures. The major expansion of pore-volume occurred between 300 and 350 °C in both samples, with the pores elongating rapidly along the organic-rich bedding. The internal pressures induced by organic matter transformation influenced the development of microfractures. Mechanical properties and strain distributions within these two samples were modelled under a range of axial stresses using Finite-element modelling (FEM). The results show that the overall stiffness of the shale reduced during heating, despite organic matter becoming stiffer. The varied roles of ductile (e.g., clay minerals, organic matter) and brittle materials (e.g., calcite, pyrite) within the rock matrix are also modelled and discussed. The configurations of organic matter, mineral components, porosity and connectivity impact elastic deformation during shale pyrolysis. This work extends our understanding of dynamic coupled processes of microstructure and elastic deformation in shales to the nm-scale, which also has applications to other subsurface energy systems such as carbon sequestration, geothermal and nuclear waste disposal.

Analyzing the development of fracture networks in shale is important to understand both hydrocarbon migration pathways within and from source rocks and the effectiveness of hydraulic stimulation upon shale reservoirs. Here we use time-resolved synchrotron X-ray tomography to quantify in four dimensions (3-D plus time) the development of fractures during the accelerated maturation of an organic-rich mudstone (the UK Kimmeridge Clay), with the aim of determining the nature and timing of crack initiation. Electron microscopy (EM, both scanning backscattered and energy dispersive) was used to correlatively characterize the microstructure of the sample preheating and postheating. The tomographic data were analyzed by using digital volume correlation (DVC) to measure the three-dimensional displacements between subsequent time/heating steps allowing the strain fields surrounding each crack to be calculated, enabling crack opening modes to be determined. Quantification of the strain eigenvectors just before crack propagation suggests that the main mode driving crack initiation is the opening displacement perpendicular to the bedding, mode I. Further, detailed investigation of the DVC measured strain evolution revealed the complex interaction of the laminar clay matrix and the maximum principal strain on incipient crack nucleation. Full field DVC also allowed accurate calculation of the coefficients of thermal expansion (8 × 10−5/°C perpendicular and 6.2 × 10−5/°C parallel to the bedding plane). These results demonstrate how correlative imaging (using synchrotron tomography, DVC, and EM) can be used to elucidate the influence of shale microstructure on its anisotropic mechanical behavior.

Silica diagenesis has the potential to drastically change the physical and fluid flow properties of its host strata and therefore plays a key role in the development of sedimentary basins. The specific processes involved in silica diagenesis are, however, still poorly explained by existing models. This knowledge gap is addressed by investigating the effect of silica diagenesis on the porosity of Cenozoic mudstones of the North Viking Graben, northern North Sea through a multiple linear regression analysis. First, we identify and quantify the mineralogy of these rocks by scanning electron microscopy and X-ray diffraction, respectively. Mineral contents and host rock porosity data inferred from wireline data of two exploration wells are then analyzed by multiple linear regressions. This robust statistical analysis reveals that biogenic opal-A is a significant control and authigenic opal-CT is a minor influence on the porosity of these rocks. These results suggest that the initial porosity of siliceous mudstones increases with biogenic opal-A production during deposition and that the porosity reduction during opal-A/CT transformation results from opal-A dissolution. These findings advance our understanding of compaction, dewatering, and lithification of siliceous sediments and rocks. Moreover, this study provides a recipe for the derivation of the key controls (e.g., composition) on a rock property (e.g., porosity) that can be applied to a variety of problems in rock physics.

Organofacies analysis, a fundamental component within source rock appraisal based on the study of kerogen within a source rock, is typically produced from microscopy (palynological) and geochemical (kerogen kinetic) data, both of which are costly to acquire. One-Run-Fixed-Arrhenius (ORFA) kerogen kinetic analysis based on Rock–Eval pyrolysis offers a substantially cheaper kinetic dataset. Here, ORFA and palynological analyses are compared in organofacies characterization of a prospective Mississippian source rock reservoir (Bowland Shale, UK). Two-end-member organofacies were determined based on the abundance of the 56 kcal/mol activation energy peak derived from ORFA data: absence (< 5%) indicating ‘organofacies A’ containing the highest proportion of algal material (Type I kerogen); and presence (> 15%) indicating ‘organofacies B’ containing the highest proportion of sporomorphs (Type II kerogen). A mud-dominated slope setting for the rock reservoir was also used to test the accuracy of organofacies analysis in determining depositional environment. Organofacies A found within lithofacies deposited from dilute waning density flows and hemipelagic suspension settling occurred between shelf edge, slope and basin. Organofacies B found within lithofacies deposited from dilute waning density flows, and low-strength cohesive debrites occurred only within the lower slope. This study demonstrates that ORFA kerogen kinetic analysis provides comparable net results to palynological analysis, enabling cheaper and faster organic characterization during initial source rock appraisal. However, caution must be exercised in drawing interpretations as to biological source(s), organic matter mixing and preservation state(s) without additional investigation using data from detailed palynological analysis.

Here we describe the first automated fully integrated in-microscope broad ion beam (BIB) system. Ar+-BIB has several advantages over Ga+ focused ion beam (FIB) and Xe+ plasma-FIB (PFIB) methods inducing less beam damage, especially for ion beam sensitive materials. It can mill areas several orders of magnitude larger (up to millimetre scale), and is not confined to the edge of the sample with associated curtaining issues. BIB is shown to have sputter rates up to five times higher than comparable FIB techniques. This new coupled BIB–SEM system (commercial name ‘iPrep™II’) enables in-microscope surface polishing to remove contaminants or damage for two dimensional (2D) imaging, as well as automated serial section tomography (SST) by milling and imaging hundreds of slices, cost and time efficiently. The milled slice thickness can be controlled from a few nanometers up to a micrometre. A novel sample transfer, handling and interlock system allows automated and sequential BIB polishing, scanning electron microscopy (SEM) and analysis by secondary electron (SE) imaging, electron back scatter diffraction (EBSD) and energy dispersive spectroscopy (EDS) for 3D microstructure analysis. Furthermore, insulating surfaces can be sputter coated after milling each slice to reduce charging during SEM analysis. The performance of the instrument is demonstrated through a series of case studies across the materials, earth and life sciences exploiting the imaging, crystallographic and chemical mapping capabilities. These include the study of butterfly defects in bearing steels, meta-stable intermetallic phases in bronze bearings, shale gas rock, aluminium plasma electrolytic oxide (PEO) coatings as well as liver and mouse brain tissues.

Despite recent advances, diagenetic processes in fine-grained sediments are still relatively poorly understood. Key questions still to be resolved include the types of diagenetic minerals present in mudstones and the extent of element mobility in these low permeability systems. This study utilizes data from the Haynesville-Bossier Shale, USA, to analyze lithologies, discriminate authigenic phase, and identify mobile elements during diagenesis. It has implications for understanding how authigenic minerals develop and the sources of those authigenic minerals in fine-grained sediments.On the basis of grain-size and mineralogy five lithologies are designated: (i) silica-rich argillaceous mudstones; (ii) argillaceous siliceous mudstones; (iii) mixed siliceous mudstones; (iv) mixed mudstones; and (v) authigenically-dominated mudstones. The diagenetic development of the Haynesville-Bossier Shale can be divided in to early and late diagenesis. Ferroan and non-ferroan dolomite, framboidal pyrite and bioclast pore-filling kaolinite and calcite grain replacements and cements all formed during early diagenesis. Late diagenetic minerals phases include illite formed by the illitisation of smectite, replacive and displacive chlorite, calcite-replacive albite, quartz-replacive calcite and replacive and/or displacive quartz.The presence of extensive late diagenetic mineral precipitates indicates that there was a degree of element mobility on at least the local scale. Aluminium present in albite is most likely to have resulted from the illitization of smectite. Quartz overgrowths probably resulted from illitization and the pressure dissolution at quartz silt grain boundaries. Externally, hydrothermal fluids resulting from regional-scale igneous activity appear to have played a role in the formation of chlorite and possibly albite. The work indicates that extensive mineral development and element mobility occurred during late diagenesis.

Understanding the speciation and fate of radium during operational discharge from the offshore oil and gas industry into the marine environment is important in assessing its long term environmental impact. In the current work, 226Ra concentrations in marine sediments contaminated by produced water discharge from a site in the UK were analysed using gamma spectroscopy. Radium was present in field samples (0.1–0.3 Bq g−1) within International Atomic Energy Agency activity thresholds and was found to be primarily associated with micron sized radiobarite particles (≤2 μm). Experimental studies of synthetic/field produced water and seawater mixing under laboratory conditions showed that a significant proportion of radium (up to 97%) co-precipitated with barite confirming the radiobarite fate pathway. The results showed that produced water discharge into the marine environment results in the formation of radiobarite particles which incorporate a significant portion of radium and can be deposited in marine sediments.

As the fastest growing energy sector globally, shale and shale reservoirs have attracted the attention of both industry and scholars. However, the strong heterogeneity at different scales and the extremely fine-grained nature of shales makes macroscopic and microscopic characterization highly challenging. Recent advances in imaging techniques have provided many novel characterization opportunities of shale components and microstructures at multiple scales. Correlative imaging, where multiple techniques are combined, is playing an increasingly important role in the imaging and quantification of shale microstructures (e.g. one can combine optical microscopy, scanning electron microscopy/transmission electron microscopy and X-ray radiography in 2D, or X-ray computed tomography and electron microscopy in 3D). Combined utilization of these techniques can characterize the heterogeneity of shale microstructures over a large range of scales, from macroscale to nanoscale (c. 100–10−9 m). Other chemical and physical measurements can be correlated to imaging techniques to provide complementary information for minerals, organic matter and pores. These imaging techniques and subsequent quantification methods are critically reviewed to provide an overview of the correlative imaging workflow. Applications of the above techniques for imaging particular features in different shales are demonstrated, and key limitations and benefits summarized. Current challenges and future perspectives in shale imaging techniques and their applications are discussed.

Biogenic CH4 generation has been observed in many shallow, low temperature shale gas basins and coal seams. The depletion of conventional resources and the increasing demand of natural gas for human consumption have spurred the development of so-called unconventional gas resources such as shale gas (SG) and coal-bed methane (CBM). Such unconventional systems represent the opportunity for the stimulation of biogenic CH4 generation. Biogenic CH4 in shale and coal is produced by anaerobic biodegradation of organic matter (OM): methanogenic Archaea represent only the final step of biogenic CH4 generation. Several communities of microorganisms are involved in the initial breakdown of complex geopolymers and the production of intermediate compounds used by methanogens. There are several key knowledge gaps on biogenic CH4 production in unconventional gas systems, such as the exact fraction of bioavailable OM, the microbial communities involved and how they can be stimulated to enhance microbial methanogenesis. Progress on biodegradation studies, isotopic signatures, as well as DNA analyses and proteomics could help unravel interactions within the syntrophic community involved in the methanogenic biodegradation of OM. Questions also remain regarding the environmental impact of unconventional gas production, such as water quality and the mobility of toxic metals and radionuclides. The answers to these questions might have implications for both recovery practices and a sustainable development of unconventional resources. This review summarises the current knowledge regarding biogenic CH4 in SG and CBM: from the nature of the rocks to the producing microbial community and the indicators of biogenic CH4, illustrating how these two environments show remarkably similar opportunities for the stimulation of biogenic CH4 generation.

Silica cementation exerts a key control on the compaction and geotechnical properties of mudstones, and byextension, the style of hydrocarbon and/or mineral systems present in a given sedimentary basin. Integratedmicroscopic and bulk geochemical observations demonstrate that siliceous mudstones in the Bowland ShaleFormation, a target for UK shale gas extraction, exhibit abundant dispersed, discrete, μm-scale quartz cements,and exhibit silica enrichment (‘excess’) above a local detrital Si/Al threshold of 2.5. Dissolution of siliceousradiolarian tests during early diagenesis is identified as the main source of silica (opal A) required for quartzprecipitation, either via opal CT or directly to quartz, and potentially generated as a product of anoxic marine‘weathering’ (dissolution) of reactive silicates during early diagenesis. Excess silica correlates with free hydrocarbons(S1) normalised to total organic carbon (oil saturation index; OSI); we propose early diagenetic quartzprecipitation suppressed pore collapse (‘buttress effect’), retaining the pore space capacity to host oil. Quartzprecipitation was likely catalysed, for example via low porewater pH, elevated Al and/or Fe oxide content, and/or abundant labile organic matter. Juxtaposition of siliceous mudstones and mudstones lacking quartz cementindicates silica was immobile beyond the bed scale. Thus metre-scale siliceous packages likely represent moreprospective units within the Bowland Shale (in terms of unconventional hydrocarbons), on the basis of earlydiagenetic biogenic-derived quartz cementation leading to improved hydrocarbon storage capacity coupled toenhanced brittleness. These findings are relevant for shale oil and shale gas systems, specifically where oilretained in pores subsequently cracks to generate gas. These findings also suggest the Bowland Shale is a subclassof black shale, defined by the potential to host a relatively large volume of early diagenetic fluids,derived from anoxic bottom waters, which were potentially S- and/or metal-bearing. This is potentially relevantfor understanding the genesis of adjacent and related Pb-Zn mineral deposits.

The Lower Permian Collyhurst Sandstone Formation is an important gas reservoir both offshore and onshore in the East Irish Sea Basin of north-western UK, and is considered to be a tight gas reservoir. Diagenetic processes have significantly influenced the reservoir quality of the sandstone. This study employs petrographic, mineralogical, and stable isotopic analyses on two different onshore core successions to investigate the composition and texture, the diagenetic history, and the impact of lithology and diagenesis on reservoir quality. The Collyhurst Sandstone Formation consists of fine- to very coarse-grained, poorly to well-sorted, sub-arkosic to lithic arenite sands. The reservoir properties of the sandstone are relatively poor, with average porosity and permeability of 6.6% and 0.387 mD respectively. On the basis of petrographic analyses, five sandstone lithofacies were identified: fine-grained, conglomeratic, carbonate-cemented, quartz-cemented and matrix-free. Contrasting characteristics between the reservoir units suggest the development of divergent diagenetic pathways. Features observed during early diagenesis include compaction, growth of pore-filling early carbonate cements (calcite I, dolomite and siderite I) and vermicular kaolinite. Late diagenetic features include: further carbonate cementations (ferroan dolomite/ankerite, calcite II and siderite II-III), clay mineral cementation (illite and chlorite) with both grain-coating and pore-filling textures. Also common in late diagenesis are syntaxial quartz overgrowths. Albite, barite and anhydrite are minor late diagenetic cement phases. Compaction processes rather than cementation accounts for the major destruction of the initial sandstone porosity. But cementation still accounts for up to 32% of porosity loss. Carbonate cements mostly fill intergranular pores, thus block pore throat and prevent migration of fluid. Clay minerals bridge and occlude pores, resulting in further destruction of the reservoir quality. The study provides insights into how lithofacies (primary composition, texture and sorting) and diagenesis can influence reservoir qualities of tight gas sandstones.

The microstructure of a highly laminated Lower Bowland Shale sample is characterized at the micron-to millimeter scale, to investigate how such characterization can be utilized for microstructure-based modelling of the shale's geomechanical behavior. A mosaic of scanning electron microscope (SEM) back-scattered electron (BSE) images was studied. Mineral and organic content and their anisotropy vary between laminae, with a high variability in fracturing and multi-micrometer aggregates of feldspars, carbonates, quartz and organics. The different microstructural interface types and heterogeneities were located and quantified, demonstrating the microstructural complexity of the Bowland Shale, and defining possible pathways for fracture propagation. A combination of counting-box, dispersion, covariance and 2D mapping approaches were used to determine that the total surface of each lamina is 3 to 11 times larger than the scale of heterogeneities relative to mineral proportion and size. The dispersion approach seems to be the preferential technique for determining the representative elementary area (REA) of phase area fraction for these highly heterogeneous large samples, supported by 2D quantitative mapping of the same parameter. Representative microstructural models were developed using Voronoï tessellation using these characteristic scales. These models encapsulate the microstructural features required to simulate fluid flow through these porous Bowland Shales at the mesoscale.

Pore characterization in shales is challenging owing to the wide range of pore sizes and types present. Haynesville-Bossier shale (USA) was sampled as a typical clay-bearing siliceous, organic-rich, gas-mature shale and characterized over pore diameters ranging 2 nm to 3000 nm. Three advanced imaging techniques were utilized correlatively, including the application of Xe+ plasma focused ion beam scanning electron microscopy (plasma FIB or PFIB), complemented by the Ga+ FIB method which is now frequently used to characterise porosity and organic/inorganic phases, together with transmission electron microscope tomography of the nano-scale pores (voxel size 0.6 nm; resolution 1–2 nm). The three pore-size scales each contribute differently to the pore network. Those 100 nm (greatest total volume hence determines fluid storativity). Four distinct pore types were found: intra-organic, organic-mineral interface, inter-mineral and intra-mineral pores were recognized, with characteristic geometries. The whole pore network comprises a globally-connected system between phyllosilicate mineral grains (diameter: 6–50 nm), and locally-clustered connected pores within porous organic matter (diameter: 200–800 nm). Integrated predictions of pore geometry, connectivity, and roles in controlling petrophysical properties were verified through experimental permeability measurements.

An understanding of the nature and scales of diagenetic variability within organic-rich mudstones is critical to the accurate assessment of shale-gas reservoir properties, as well as for elucidating chemical evolution pathways within mudstones. Here we integrate field observations with thin section descriptions (optical and electron optical techniques) and mineralogical data for the Blackhawk Member time-equivalent Mancos Shale in Book Cliffs, Utah, to determine the impacts of early and burial diagenesis on this mudstone succession.The detrital assemblage in the Mancos Shale comprises quartz-silt, feldspar, clay minerals, dolomite and organic matter (TOC of 1 to 2.5%). Biogenic silica is negligible. Field mapping reveals laterally continuous (km scale), ferroan dolomite cemented units up to 0.3 m thick, are present. These cemented units cap both coarsening-upward units (1 to 3 m thick), and stacked successions of coarsening-upward units (5 to 15 m thick). These upward-coarsening sediment packages, capped by dolomite cemented strata, correlate to bedsets and parasequences in updip settings. Pervasive cementation in these dolomite-cemented units is likely to have occurred prior to compaction as a result of bacterially mediated respiratory processes. Cementation at these levels is particularly evident because cement precipitation occurred during breaks in sediment accumulation below marine flooding surfaces. The abundance of dolomite cements highlights the importance of macroscopic-scale diagenetic carbonate mobility in these mudstones.In addition to carbonate-cements, diagenetic alteration and precipitation of quartz and alumina-silicate minerals are also important in these mudstones. Kaolinite is present both in uncompacted test of organisms and as vein fills in septarian concretions. Kaolinite precipitation is interpreted to have occurred prior to significant compaction and indicates that both silicon and aluminium were mobile during early diagenesis. We interpret the abundance of early diagenetic kaolinite cement to be the result of Al-mobilization by organic acids generated during organic matter oxidation reactions, with the Al sourced from poorly crystalline detrital aluminium oxides and clay minerals. There is also indirect evidence for burial diagenetic kaolinitization of feldspar grains. Quartz cement takes the form of quartz overgrowths and microcrystalline quartz crystals. Textures and CL spectra for the quartz microcrystalline cement suggests that recrystallization of biogenic silica (opal-A) was likely to have been an important source for quartz cements, although smectite-to-illite transformation may have contributed some. These mineral phases highlight that microscopic-scale diagenetic mobility of silica is important, even within mudstones lacking obvious sources of biogenic silica and is likely to be an important processes in a wide range of mudstones.

In sandstone reservoirs, despite grain rearrangement during compaction, significant pore volumes may be retained prior to the onset of late diagenetic quartz cementation. In mudstone reservoirs, grain rearrangement during compaction results in significant pore volume reduction prior to late diagenesis. Where quartz overgrowths have been previously reported in post-compaction mudstones they have been in volumetrically low concentrations and interpreted as anomalous occurrences. Quartz cementation alters rock brittleness resulting in changes to mechanical fracture properties. Quartz overgrowths reduce reservoir porosity and permeability. We present petrographic evidence of two phases of quartz cement in the Haynesville-Bossier Shale: (i) grain replacive and (ii) quartz overgrowths. Carbonate grain replacement is volumetrically low (< 1%). Quartz overgrowths identified from SEM-CL imaging are volumetrically more significant (8–13%). Quartz overgrowths were most commonly observed in the coarse mudstone microfacies, but are present in both medium and fine mudstone microfacies. Petrographic evidence indicates three processes in the development of quartz overgrowths. Mica and pyrite are (i) engulfed and (ii) displaced by quartz overgrowth cement. The absence of a supportive, primary granular framework surrounding engulfed detrital and early authigenic minerals would indicate that quartz overgrowths are also replacive. Pressure dissolution of quartz silt grains and smectite-to-illite transformation are likely sources of silica for quartz cement. This study is the first to document large-scale, replacive, authigenic quartz overgrowth development within a producing mudstone.

Well-preserved fossils of pivotal early bird and nonavian theropod species have provided unequivocal evidence for feathers and/or downlike integuments. Recent studies have reconstructed color on the basis of melanosome structure; however, the chemistry of these proposed melanosomes has remained unknown. We applied synchrotron x-ray techniques to several fossil and extant organisms, including Confuciusornis sanctus, in order to map and characterize possible chemical residues of melanin pigments. Results show that trace metals, such as copper, are present in fossils as organometallic compounds most likely derived from original eumelanin. The distribution of these compounds provides a long-lived biomarker of melanin presence and density within a range of fossilized organisms. Metal zoning patterns may be preserved long after melanosome structures have been destroyed.

The sediments in the Salford Quays, a heavily-modified urban water body, contain high levels of organic matter, Fe, Zn and nutrients as a result of past contaminant inputs. Vivianite [Fe3(PO4)2 · 8H2O] has been observed to have precipitated within these sediments during early diagenesis as a result of the release of Fe and P to porewaters. These mineral grains are small (

Sub-tidal, reef-lagoon surficial sediment samples from Discovery Bay, north Jamaica were analysed in order to quantify the impacts of anthropogenic bauxite inputs on trace metal (Fe, Zn, Mn) levels and sediment characteristics. Contaminant levels exhibit marked spatial variations, but are highest across central and southern parts of the bay and primarily reflect wind blown inputs, modified by subsequent suspended sediment transport. Highest contaminant levels (Fe—13,701 ppm, Mn—237 ppm, Zn—74 ppm) occur immediately adjacent to, and just north-east of, a bauxite loading terminal in the south-west of the bay. Sites of high sediment contamination are negatively correlated with per cent CaCO3 content, indicating the diluting effect of bauxite on the carbonate substrate. At high contamination sites CaCO3 levels are reduced to 63.7% and are in the range of 75–80% across much of the central and southern area of the bay. Magnetic susceptibility level measurements are positively correlated with iron and n...

This study investigates the application of high sensitivity electron spin resonance (ESR) to environmental magnetism in conjunction with the more conventional techniques of magnetic susceptibility, vibrating sample magnetometry (VSM) and chemical compositional analysis. Using these techniques we have studied carbonate sediment samples from Discovery Bay, Jamaica, which has been impacted to varying degrees by a bauxite loading facility. The carbonate sediment samples contain magnetic minerals ranging from moderate to low concentrations. The ESR spectra for all sites essentially contain three components. First, a six-line spectra centred around g= 2 resulting from Mn2+ ions within a carbonate matrix; second a g= 4.3 signal from isolated Fe3+ ions incorporated as impurities within minerals such as gibbsite, kaolinite or quartz; third a ferrimagnetic resonance with a maxima at 230 mT resulting from the ferrimagnetic minerals present within the bauxite contamination. Depending upon the location of the sites within the embayment these signals vary in their relative amplitude in a systematic manner related to the degree of bauxite input. Analysis of the ESR spectral components reveals linear relationships between the amplitude of the Mn2+ and ferrimagnetic signals and total Mn and Fe concentrations. To assist in determining the origin of the ESR signals coral and bauxite reference samples were employed. Coral representative of the matrix of the sediment was taken remote from the bauxite loading facility whilst pure bauxite was collected from nearby mining facilities. We find ESR to be a very sensitive technique particularly appropriate to magnetic analysis of ferri- and para-magnetic components within environmental samples otherwise dominated by diamagnetic (carbonate) minerals. When employing typical sample masses of 200 mg the practical detection limit of ESR to ferri- and para-magnetic minerals within a diamagnetic carbonate matrix is of the order of 1 ppm and 1 ppb respectively, approximately 102 and 105 times the sensitivity achievable employing the VSM in our laboratory.

Sediments are a major component of the ocean system and the composition of, and chemical processes acting upon, these sediments are controlled by many factors. In this chapter we outline the major types of marine sediment (lithogenous, biogenic, hydrogeneous and authigenic), discuss the sources of these and their chemical and mineral characteristics. The most abundant minerals are (oxyhydr)oxides, clay minerals, sulfides and carbonates, and all of these have been studied extensively, using a range of mineralogical techniques. A major aim of this chapter is to provide a framework by which the mineral transformations that take place upon, or just below, the sea-floor can be understood. There are significant thermodynamic, kinetic and biological controls on these transformations, and the interaction of these plays a major role in element cycling between the oceans and the lithosphere, and trace element-enrichment on the sea-floor and carbon burial and remineralization. Further, we conclude that more research is required on the interactions between minerals and bacteria within marine sediments, and on the role of amorphous oxide minerals delivered from land in early burial reactions and mineral precipitations.Oceans cover ∼70% of the Earthâ∈™s surface so that the processes operating within the marine realm and upon ocean floors play a marked role in element and nutrient cycling, biological productivity, ultimately exerting an important influence on global climate. This chapter will focus on the distribution, composition and mineralogy of sediments that are actively accumulating on the sea floor, both in the shallow marine and deep ocean realms. Further, it will describe the geochemical and mineralogical processes operating in these sediments.

Atmospheric deposition of trace metals and metalloids from anthropogenic sources has led to the contamination of many European peatlands. To assess the fate and behaviour of previously deposited arsenic and lead, we constructed catchment-scale mass budgets for a degraded peatland in Northern England. Our results show a large net export of both lead and arsenic via runoff (282 ± 21.3 gPb ha −1 y −1 and 60.4 ± 10.5 gAs ha −1 y −1 ), but contrasting controls on this release. Suspended particulates account for the majority of lead export, whereas the aqueous phase dominates arsenic export. Lead release is driven by geomorphological processes and is a primary effect of erosion. Arsenic release is driven by the formation of a redox-dynamic zone in the peat associated with water table drawdown, a secondary effect of gully erosion. Degradation of peatland environments by natural and anthropogenic processes has the potential to release the accumulated pool of legacy contaminants to surface waters.

Linear relationships between regional water quality and catchment characteristics (terrain, land cover, geology, base flow index and rainfall) are examined for rivers in North West England using a GIS-based approach and an extensive Environment Agency water quality database. The study considers the role of diffuse and distal point sources on river water quality. The results show that base cation concentrations are strongly linked to catchment terrain and land cover, while pH is linked to bedrock geology and land cover. Mean nitrate concentrations are most strongly related to arable cover, although distal point sources in urban and rural catchments appear to have a significant effect on river nitrate concentrations in the region. Orthophosphate and suspended sediment concentrations are most closely related to the percentage urban development. Linear models are tested on a large independent water quality dataset, resulting in maps showing predicted water quality across the region. The approach works well for the prediction of nitrate concentrations and other constituents which have predominantly diffuse sources. In contrast, the linear approach to predicting orthophosphate concentrations in North West rivers using catchment characteristics is problematic. The major influence of point sources may mask the effect of wider basin attributes on orthophosphate concentrations. Within-river processing of phosphorus may also explain why the relationship breaks down. Further work is needed to explain phosphorus contributions and variability in North West rivers, especially in the context of effective catchment management.

An extremely well-preserved dinosaur ( Cf. Edmontosaurus sp.) found in the Hell Creek Formation (Upper Cretaceous, North Dakota) retains soft-tissue replacement structures and associated organic compounds. Mineral cements precipitated in the skin apparently follow original cell boundaries, partially preserving epidermis microstructure. Infrared and electron microprobe images of ossified tendon clearly show preserved mineral zonation, with silica and trapped carbon dioxide forming thin linings on Haversian canals within apatite. Furthermore, Fourier transform infrared spectroscopy (FTIR) of materials recovered from the skin and terminal ungual phalanx suggests the presence of compounds containing amide groups. Amino acid composition analyses of the mineralized skin envelope clearly differ from the surrounding matrix; however, intact proteins could not be obtained using protein mass spectrometry. The presence of endogenously derived organics from the skin was further demonstrated by pyrolysis gas chromatography mass spectrometry (Py-GCMS), indicating survival and presence of macromolecules that were in part aliphatic (see the electronic supplementary material).

PurposeChromium, a potentially harmful element, occurs commonly within the urban sediment cascade as a result of abundant industrial and transport-related sources. The risks that Cr-bearing particles pose to ecosystems and humans depend on the solid-phase chemical speciation of Cr and its environmental mobility. In this study, we adopt an integrated geochemical approach to investigate and determine the long-term fate of Cr in the urban sediment cascade.Materials and methodsWe use bulk chemical digests, sequential chemical extraction analysis, electron microscopy, electron microprobe and microfocus XANES analysis to describe the solid-phase speciation, geochemical characteristics and potential long-term behaviour of Cr in urban particulate matter from both aquatic sediment and road dust sediment (RDS) in Manchester, UK.Results and discussionCr-bearing grains within RDS and aquatic sediment are predominantly iron oxides and alumino-silicate glass grains. Electron microprobe analysis indicates Cr concentrations up to 3300 and 133,400 μg g−1 in the RDS and aquatic grains, respectively. XANES analysis indicates that Cr(III) is the dominant oxidation state, with only trace amounts of Cr(VI). Importantly, Cr speciation does not appear to have changed between sedimentary environments and the dominance of Cr(III) suggests limited bioavailability or toxicity under predominant environmental (anoxic and neutral pH) conditions in the aquatic sediment sink. Furthermore, geochemical analyses suggest the environmental mobility of Cr in the aquatic sediment sink is low (compared to other toxic metals) due to its association mainly with alumino-silicate glass grains and its inclusion as an integral part of the glass structure.ConclusionsIndustrial glass grains are a major component of urban sediment worldwide. The speciation and geochemical investigations performed in this study suggest most Cr within the urban sediment cascade may be resistant to environmental processes that could mobilise other toxic metals.