Parent Sand Research Articles

On the modelling of stress-dilatancy behavior in weakly cemented sands

A comprehensive study on the stress-dilatancy behavior of cemented sand and its modeling is presented. The effect of confining pressure, relative density, and cement content on stress-dilatancy behavior are studied from the published experimental results and an additional series of experiments performed in this study. To facilitate a contrast and comparison of stress-dilatancy behavior between these datasets, a normalized stress ratio is proposed which removes the effect of mineralogy and morphology of parent sand. A set of key insights were obtained from this comparative study which aided in improving the stress-dilatancy relation; for example, the effect of initial conditions on stress-dilatancy behavior was found to be captured by the ratio of cohesion intercept (or tensile strength) and mean effective stress before shearing. The limitations of stress transformation, often used in modelling of cemented sand, were also systematically studied by a set of carefully designed experiments; it was found to be only applicable before gross yielding of cementation. After gross yielding, it is necessary to take in account of the breakage of bonds/cementation. The gross yield locus was identified from 70 experimental datasets and a cohesion/bond degradation model was formulated to model the stress-dilatancy behavior of cemented sand. The efficacy of stress-dilatancy relations (after including the gross yield locus and bond degradation behavior) is evaluated from the experimental results; the Rowe's stress-dilatancy relation was found to be most suitable with the proposed bond/cohesion degradation model.

Liquefaction Resistance of Sand-Kaolin Mixtures: Effect of Sand Sizes

Grading characteristics, particle sizes, particle shapes and fines content are the factors contributing to liquefaction incidents besides major factors such as earthquake magnitude. Recent publications and reports from incidents of liquefied or potential liquefied soils show some evidence that the size of sand particles, particle shapes and grading characteristics will increase or decrease the liquefaction resistance. However, to date the results are still disputed and need to be expanded. Hence, the aim of this paper is to investigate the effects of different sizes of sand in sand-kaolin mixtures on liquefaction resistance. The liquefaction resistance of sand mixtures with the application of different sizes of sand-coarse sand, medium sand and fine sand mixed with fines (kaolin) content (0%,10%, 20%, 30%, and 40%) are investigated through a cyclic triaxial test under undrained conditions. Each reconstituted sample was prepared with a target relative density of 15% (loose state) and 5% of initial moisture content for the triaxial test. Effective consolidation pressures of 100 kPa were applied on the cyclic triaxial tests. Microstructure analysis on the soil samples were carried out to explain the behaviour of the samples tested. The centrifuge test was carried out on selected samples so that the behaviour of the soils in actual conditions could be visualised. The results clearly show that the liquefaction resistance was reduced at reduced sand sizes. At a constant fines content for each parent sand, the liquefaction resistance decreased with an increase of fines content up to certain percentage, then increased thereafter. The fth decreased from 30% to 20% of fines content with a decrease in parent sand sizes. The outcomes of this study are useful to advance the understanding of the behaviour of sand mixtures with different sizes of sand for design purposes.

Ecology of the northern mole vole (Ellobius talpinus) in the central regions of its range: characteristics of habitats in areas of the species’ occurence

Burrowers are the main creators, converters, and keepers of landscapes and soils of steppe ecosystems. The northern mole vole Ellobius talpinus (Pallas, 1770) is a rather widespread species of burrowing animals, an indicator species of various types of steppes, with a pronounced environment-forming activity. Fourteen large colonies of E. talpinus were studied in the Middle Volga region during the field seasons of 2006–2021. The agrochemical indicators of the soil characterise the possibility of developing certain steppe microstations, in which specific plant associations are formed. The parameters of soil samples and their combinations show the suitability of the formation of those plant associations that will correspond to the conditions of existence, reproduction, and feeding of burrowing rodents, in this case, the northern mole vole. The agrochemical features of steppe landscapes and habitats of the northern mole vole E. talpinus in the Middle Volga region are considered as stable trends in the formation of steppe communities. The northern mole vole E. talpinus prefers soils with a neutral or slightly alkaline pH, moderate phosphorus and calcium content, high copper and manganese content, moderate zinc content, uncontaminated by heavy metals (sometimes with an excess of cadmium content in the ancient layers of the parent rock) and rather loose (from loose sand and sandy loam to light and medium loam), which is easily carried out when digging the burrow, easily digs and deepens, for arranging chambers and passages, when extracting rhizomes, tubers, and bulbs of fodder plants. In the studied region, the steppe mole vole is generally attached to steppe and steppe landscapes, forb-feather grass-fescue steppes on parent sand and sandstone, chalk rocks; it chooses burrowing sites with steppe vegetation of various options, preferring calciphilic and psammophilic associations. The mole vole, as well as other burrowing rodents, are indicators of steppe landscapes and the preservation of soil in their biotopes, which, in turn, are indicators of the preservation of steppe habitats. The type of soil, its main features, as well as landscape characteristics of the habitat are important regional diagnostic characters of E. talpinus colonies.

Monotonic, cyclic and post-cyclic shearing behavior of sand-EPS geofoam interface

Sand-EPS geofoam is commonly used as a seismic buffer in a variety of geotechnical applications to alleviate damages imposed by seismic vibrations. Evaluation of the properties of the sand-EPS geofoam interface is an essential part of the design and installation of EPS geofoam in direct contact with the parent sand. In this study, a series of laboratory tests are carried out using a large-scale direct shear apparatus to evaluate the monotonic, cyclic and post-cyclic behavior of the sand-EPS geofoam interface. Adopting the relative density of the parent sand, the density of EPS geofoam, the applied normal stress, the cyclic shear strain semi-amplitude and the number of cycles as the variable parameters, their influence on the response of the sand-EPS geofoam interface is investigated. According to the experimental results, with the increase in the number of cycles, sand relative density, EPS geofoam density and the applied normal stress, the equivalent or secant stiffness of the sand-EPS geofoam interface increases while its damping ratio declines. The results of the monotonic (MDS) and post-cyclic monotonic (CMDS) shearing experiments also show that with an increase in the EPS density and normal stress, which offers greater resistance against sliding, the mobilized shear stresses generally increase.

The Norwegian–Danish Basin: a dynamic setting for subsurface sand remobilization – established concepts on distribution and controlling factors

Abstract The Norwegian–Danish Basin is characterized by a depositional environment governed by incised valleys, localized sand deposition and rapid progradation of thick sediment packages during the Paleogene and Neogene. Subsurface sand injectites occur at five locations, with distinctive geometries and injection styles. Such vary from short-distance injectites where injected dykes and sills are in direct contact with the parent sand, to a long-distance sand extrudite >1 km vertically above the proposed parent sand. These endmembers establish the Norwegian–Danish Basin as a dynamic environment for subsurface sand remobilization. Although formation models exist for the injectites at each of the five locations, general considerations of sand injection mechanisms in the Norwegian–Danish Basin remain untested. This study presents a synthesis of geometrical characteristics, sand injection style and controlling factors for sand injection in the Norwegian–Danish Basin. By reviewing the existing literature and including new data, the study qualitatively addresses the effects of parent-sand distribution on injection style at the five locations, the overpressure generating mechanisms and the importance of faulting as a trigger mechanism. The results show that short-distance injectites typically occur in areas with a confined parent sand and that salt-related faulting is locally important as a trigger mechanism for sand remobilization. The main overpressure generating mechanism is differential loading and lateral transfer of pressure. The case studies also show a trend between larger depocentres required for remobilization of more distal parent sands relative to the depocentre. The results confirm the prevailing consensus that local conditions related to parent sand distribution and burial depth partly control injection geometry and style.

Sand injectites: from source to emplacement – an example from the Miocene age Frimmersdorf Seam, Garzweiler Open-cast Mine, Lower Rhine Embayment

Abstract Sand injectites are reported from a Miocene-age lignite seam in the Lower Rhine Embayment, which is exploited in the Garzweiler open-cast mine, Germany. Owing to the ongoing mining of the seam, the sand injectite morphology and extent were documented over a 3 year period. The combination of fieldwork, geophysical and drilling well data, as well as a 3D reconstruction of the host unit, reveal that the sand injectites within the Frimmersdorf Seam (= host unit) are highly variable, and include sills, dykes, reticulate (i.e. an interconnected network of thin sand veins) and irregular-shaped sand bodies. The injectites are connected to the underlying Frimmersdorf Sand or the overlying Neurath Sand (= parent sand units), or can be distributed throughout the seam. The differentiation of sand injectites from syn-depositional sand bodies is based on the orientation (discordant/concordant) and the presence of primary sedimentary structures in the latter. The prevailing stress field across the Lower Rhine Basin, and the coeval nature of fault activity, controlled the formation of sand injectites in the region. While such structures have been noted for over 30 years, this study is the first to provide a detailed analysis of these economically important features, including their classification, extent and morphology.

Reconstruction of subsurface sand remobilization from seismic data

Abstract Sand remobilization often occurs in deltaic depositional environments as a result of sediment load and de-watering during sediment compaction. Three-dimensional seismic data from a shelf and fan delta environment in the Central North Sea are interpreted using a colour processing technique which gives clues for reconstructing the depositional environment and remobilizing the sand. The shape and thickness of the sand remobilization features appear to be influenced by the depositional environment of parent sand. In the shallow part of the fan delta, irregular injectite geobodies are observed. In the proximal fan delta, large round saucer-shaped injectites indicate that the pressure release largely occurred in a crater-like shape. With increasing distance from the shelf break, the thickness of the sediment load and, thus, the pressure increases. Thin and extensive sheet-like injectite structures develop along faults. Some of these appear to reactivate pre-existing flanks of giant pockmarks.

Relationship between bowl-shaped clastic injectites and parent sand depletion: implications for their scale-invariant morphology and composition

Abstract Three-dimensional seismic reflection data provide a means to assess the impact of injection on parent sands, and to quantify the character of the resulting injectite networks. The morphology of a series of large injectite structures hosted in the Paleocene Lower Lista Formation were mapped using broadband 3D seismic data from the North Sea to investigate their relationship with parent sands. Fourteen bowl-shaped structures were identified within the Lista Formation in the study area (60–85 m in height, and 200–900 m in width). Sand is absent (below resolution) below these large-scale bowls, suggesting that the parent sand is the underlying Maureen Formation and that sand ‘welds’ formed, rather than sand-prone channelized deposits within the Lista Formation. Identification of injectite networks can be ambiguous, which impacts geological model development. Observations from exhumed systems and core offer high-resolution insights into the complexity of injectite networks. To advance our understanding of this scale gap, we argue for injectites being scale invariant in their shape and grain size. This permits the application of outcrop-scale knowledge to seismic-scale interpretation. The demonstrable depletion of parent sands, and their scale invariance, can be applied to basin-fills worldwide to reduce uncertainties of the impact of sand injectites on hydrocarbon reservoirs.

Effect of Anisotropic Stress State on Elastic Shear Stiffness of Sand–Silt Mixture

Soil stiffness is a critical property in the evaluation of earth structure deformation and its accurate estimation is an essential part of any geotechnical investigation. In this study, the significant contribution of non-plastic silica fines content in the relationship between small-strain shear modulus and stress anisotropy of silty sands is investigated through a comprehensive set of bender element tests. All the samples of the study were created in the laboratory and tested in a stress path triaxial apparatus applying isotropic and anisotropic stress paths. The mixtures had variable contents of sand and a non-plastic silica silt. Data analysis demonstrated that the exclusive effect of fines content on the changing rate of elastic shear modulus due to anisotropic stress state turns out to be considerable and increasing for all the tested parent sands up to a specific silt portion, about 20%, after which this effect becomes negligible. Using the experimental results, the previously proposed expression for the prediction of the small-strain shear modulus under stress anisotropy for granular materials is extended to sand–silt mixtures. A comparison of the measured against the predicted elastic shear moduli under stress anisotropy, demonstrated that the concept of the skeleton (granular) void ratio could not be applied effectively in the evaluation of the dynamic behaviour of sand–silt mixtures.

A climosequence of chronosequences in southwestern Australia

SummaryTo examine how climate affects soil development and nutrient availability over long timescales, we studied a series of four long‐term chronosequences along a climate gradient in southwestern Australia. Annual rainfall ranged from 533 to 1185 mm (water balance from −900 to +52 mm) and each chronosequence included Holocene (≤ 6.5 ka), Middle Pleistocene (120–500 ka) and Early Pleistocene (∼2000 ka) dunes. Vegetation changed markedly along the climosequence, from shrubland at the driest site to Eucalyptus forest at the wettest. Soil pH was similar in the youngest soil of each chronosequence, although the carbonate and P contents of the parent sand declined from dry to wet along the climosequence, presumably linked to variation in offshore productivity. Despite this, soil development and associated nutrient status followed remarkably consistent patterns along the four chronosequences. Pedogenesis involved decalcification and secondary carbonate precipitation in Holocene soils and leaching of iron oxides from Middle Pleistocene soils, leading ultimately to bleached quartz sands in the oldest soils. Along all chronosequences soil pH and total P declined, whereas C:P and N:P ratios increased, which is consistent with the predicted change from N to P limitation of vegetation during ecosystem development. The expected unimodal pattern of leaf area index was most pronounced along wetter chronosequences, suggesting an effect of climate on the expression of retrogression. The four chronosequences do not appear to span a pedogenic climate threshold, defined as an abrupt change in soil properties across a relatively small change in climate, because exchangeable phosphate and base cations declined consistently during long‐term pedogenesis. However, the proportion of total P in organic form was greater along wetter chronosequences. We conclude that soil and nutrient availability on the coastal sand plains of southwestern Australia change consistently during long‐term pedogenesis, despite marked variation in modern vegetation and climate. The four chronosequences provide a rare soil‐age × climate framework within which to study long‐term ecosystem development.Highlights We describe four long‐term coastal dune chronosequences spanning a climate gradient in a global biodiversity hotspot. Pedogenesis involves depletion of phosphorus and cations linked to decalcification and subsequent podsolization. Climate has relatively little effect on patterns of nutrient availability during ecosystem development along the climosequence. The age by climate framework enables study of effect of edaphic change on above‐ and below‐ground communities.

Uptake of Hexavalent Chromium in Electroplating Wastewater by Hydrothermally Treated and Functionalized Sand and Its Sustainable Reutilization for Glass Production

Sand used for glass production was first hydrothermally treated in a sodium hydroxide solution followed by silica coating that created nanoporosity in the residual sand particles increasing the surface area by ca. 740 times when compared to parent sand particles. The hydrothermally treated sand was named as reconstructed sand (R-sand) and was further functionalized with 3-aminopropyltriethoxysilane (F-Sand) and both sands were later used as adsorbents to remove toxic chromium from aqueous solutions. The influence of pH, initial ion concentration, contact time, adsorption temperature, and dosage of adsorbent on the adsorption performance of both sands were investigated and compared. The kinetics of Cr6+ adsorption by both sands follows the pseudo-second-order kinetic model, while the adsorption of Cr6+ of R-sand and F-sand fits Langmuir and Freundlich models, respectively. The F-sand has shown improved adsorption performance and was used to adsorb chromium from electroplating wastewater. Since the hydrothe...

An integrated model of clastic injectites and basin floor lobe complexes: implications for stratigraphic trap plays

AbstractInjectites sourced from base‐of‐slope and basin‐floor parent sandbodies are rarely reported in comparison to submarine slope channel systems. This study utilizes the well‐constrained palaeogeographic and stratigraphic context of three outcrop examples exposed in the Karoo Basin, South Africa, to examine the relationship between abrupt stratigraphic pinchouts in basin‐floor lobe complexes, and the presence, controls, and character of injectite architecture. Injectites in this palaeogeographic setting occur where there is: (i) sealing mudstone both above and below the parent sand to create initial overpressure; (ii) an abrupt pinchout of a basin‐floor lobe complex through steep confinement to promote compaction drive; (iii) clean, proximal sand beds aiding fluidization; and (iv) a sharp contact between parent sand and host lithology generating a source point for hydraulic fracture and resultant injection of sand. In all outcrop cases, dykes are orientated perpendicular to palaeoslope, and the injected sand propagated laterally beneath the parent sand, paralleling the base to extend beyond its pinchout. Understanding the mechanisms that determine and drive injection is important in improving the prediction of the location and character of clastic injectites in the subsurface. Here, we highlight the close association of basin‐floor stratigraphic traps and sub‐seismic clastic injectites, and present a model to explain the presence and morphology of injectites in these locations.

Discussion on ‘Late Cenozoic geological evolution of the northern North Sea: development of a Miocene unconformity reshaped by large-scale Pleistocene sand intrusion’, Journal of the Geological Society , 170, 133–145

In their recent paper, Loseth et al . (2013) propose a new model for the late Cenozoic evolution of the northern North Sea. They propose that during the early Pleistocene ( sensu ICS 2013), large volumes of sand were ejected from the Paleocene through the Eocene–Oligocene Hordaland Group, and deposited both as extrusive sand on the Pleistocene seafloor and as intrusive sand within the Oligocene section, c . 180 m below the seafloor. The paper builds on two earlier studies: (1) that by Loseth et al . (2012) in which the Pleistocene extrusive sand is presented in more detail; (2) that by Rodrigues et al . (2009) in which an experimental model related to such sand deposition is presented. The model of Loseth et al . (2013) is illustrated by a seismic section in their figure 12, showing intrusive sands within the Oligocene and extrusive sands within the Pleistocene. Details of this model, such as feeder dykes and blowout fissures that create ditches, are shown in their figure 8 (Visund Field) and figure 11 (Snorre Field). The geological events are summarized in their figure 16. As illustrated on a stratigraphic scheme (their figs 2 and 15), Loseth et al . interpret the Oligocene sands as being injected from a Paleocene parent sand. They propose that the mounds at the top of the Hordaland Group resulted from forced folding over the sand injectites, as exemplified in their figure 11. Furthermore, Loseth et al . interpret escarpments on the Top Hordaland Group Unconformity as cliff sections similar to those of southeastern England today and claim that the northern North Sea was subaerially exposed during a 10 myr Miocene time span. Loseth et al . (2012, 2013) not only challenge our previous turbiditic interpretation of the Pleistocene sand (Eidvin & …

Indicators of propagation direction and relative depth in clastic injectites: Implications for laminar versus turbulent flow processes

Clastic injectites are widely recognized in deep-water stratigraphic successions, although their sediment transport processes, propagation direction, and depth of injection are poorly constrained. Understanding how they form is important, as injectites are increasingly being recognized as significant components of sedimentary basin fills, yet are not predicted by standard sedimentary facies models. Here, analysis of features on the margins of exhumed clastic sills and dikes, and clasts within them, enables their genesis to be determined. A diverse array of diagnostic structures is found on the margins of injectites in the Karoo Basin, South Africa, where the net direction of injection and position of the parent sand are well constrained. Injectite margin features include mudstone clast–rich surfaces, planar or smooth surfaces, blistered surfaces, and parallel and plumose ridged surfaces. Combined, these features are critical in distinguishing injected sands, where injectites are strata concordant, from those of primary deposition. All features are indicative of propagation through brittle, very fine-grained sediments at depths where the applied shear stress is at least four times the tensile strength of the host rock. Additionally, the presence of parallel ridges, plumose ridges, and steps allows local fracture propagation to be constrained, and in turn injection direction. The features described provide evidence that sands were injected at considerable depth in closed fractures with limited capacity for flow dilution and turbulence enhancement. Calculated Reynolds numbers, lack of erosion at injectite walls, and the presence of mud clasts at the top and base of sills indicate that many flows were likely fully laminar during injection. The sedimentary features of these confined, relatively deep, laminar flow–induced injectites are very different from injectites that reach the surface and produce extrudites. Surface-linked injectites are associated with open conduits where a greater fraction of carrier fluid to particles can be accommodated, enabling highly turbulent, lower-concentration flows.

Soil phosphorus fractionation and nutrient dynamics along the Cooloola coastal dune chronosequence, southern Queensland, Australia

The amounts and forms of soil phosphorus (P) follow predictable patterns during long-term pedogenesis, but have rarely been examined along subtropical chronosequences. We quantified changes in soil nutrient stocks, foliar nutrient concentrations, and the chemical forms of soil P along the Cooloola chronosequence, a series of coastal dunes spanning ca. 500,000years of pedogenesis in subtropical Queensland. The total P stock in the upper 30cm of the soil profile declined continuously with soil age, from 229–237kgha−1 on the youngest soils (40years old) to 24–28kgha−1 on the oldest soils (195–>460ka). In contrast, total carbon (C) and nitrogen (N) stocks increased initially along the chronosequence and then declined in the oldest soils. As a consequence, soil N:P ratios increased continually throughout the sequence, from ≤4 on the youngest soils to 27–30 on the oldest soils. This indication of increasing biological P stress and ultimately P limitation was further supported by a decline in foliar P concentrations and increasing foliar N:P ratios of two common plant genera along the chronosequence. Sequential P fractionation revealed that although all forms of P declined during pedogenesis, young soils contained low concentrations of primary mineral P and relatively high concentrations of occluded P associated with secondary minerals, suggesting that the parent sand originated from strongly-weathered continental soils. We conclude that the Cooloola chronosequence is an important example of long-term ecosystem development under a subtropical climate, although the pre-weathered nature of the parent sand indicates that the sequence represents a modification of the Walker and Syers model of P transformations during pedogenesis.

Weathering of glauconite in soils of temperate climate as exemplified by a Luvisol profile from Góra Puławska, Poland

The aim of the research reported herein was to study the weathering of glauconite taking place in a Luvisol profile developed on quartz-glauconitic sand in Góra Puławska (eastern Poland) using X-ray diffractometry, Fourier transform infrared spectroscopy, Mossbauer spectroscopy, SEM–EDS, and an optical microscope. The bulk soil material contains quartz, glauconite, glauconite–smectite mixed-layered minerals rich in smectite layers, and traces of feldspars. When compared with the parent material (the Cg horizon), the Bt1 and Bt2 horizons are enriched in clay minerals while the Ap, AEg, and E horizons are depleted in clays. The observed mineral distribution is most likely controlled by the weathering of clay minerals in the uppermost part of the profile and translocation of clay fractions down the profile (lessivage). However contamination with glaciofluvial and/or aeolian material has to be taken into consideration. According to the microscopic observations of the thin sections clay is present in the BCg and Cg horizons in the form of clay coatings and clay infilings. This indicates that initially the parent sand did not contain clay fraction. The fraction was formed most likely in the upper part of the soil profile and was deposited in the lower horizons by percolating atmospheric water. Green pellets separated from all the soil horizons are composed of glauconite showing more or less uniform chemical composition, while clay fractions from all the horizons contain glauconite and glauconite–smectite. Fine clay fractions separated from Ap and AEg horizons are enriched in glauconite–smectite relative to the fractions separated from the lower horizons. The presence of glauconite and glauconite–smectite minerals in the clay fractions studied indicates that glauconite weathering in the soil studied involves formation of glauconite clay by the pellet disintegration and glauconite smectitization. Ferrous iron accounts only for <0.1 layer charge per half unit cell in the primary glauconite. This indicates that ferrous iron oxidation is not the main mechanism leading to the glauconite smectitization. Because the glauconite–smectite appears to be depleted in magnesium and total iron and enriched in aluminum and silicon relative to primary glauconite, leaching of magnesium and iron together with possible reorganization of the structure appears to be the likely mechanism for the glauconite smectitization.

Iron‐rich nanoparticles formed by aeolian abrasion of desert dune sand

Iron‐rich nanoparticles in aeolian mineral dust are of considerable importance to biogeochemical cycles. A major determinant of the chemical characteristics of nanoparticles is the parent sediment they are sourced from. The abrasion of dune sand has previously been shown to produce coarse dust (&gt;1 μm) during the occurrence of aeolian saltation. In this study, Australian red dune sands were laboratory abraded and emission of particles 18–414 nm was observed throughout the experiment duration (∼1 h). The mean size of particles was 130 nm at the start of the test, but this gradually decreased to 110 nm at the end. The number concentration of particles approximately trebled over the course of the experiment with results suggesting that collisions between mobile sand grains led to the production of new nanosized particles over time. Chemical analysis revealed that these nanoparticles were highly abundant in iron, with some aluminium present. This chemical composition suggests that nanoparticles are produced from the clay coatings surrounding the parent sand grains. The study shows that abrasion from saltation occurring in Australian dune sands can release iron‐rich nanoparticles, making them available for downwind transport during blowing dust events.

Biogeochemical cycling of soil phosphorus during natural revegetation of Pinus sylvestris on disused sand quarries in Northwestern Russia

Quarrying causes severe degradation of soils and vegetation that can be recovered partially when the quarries are abandoned and re-colonised by plants. To understand the recovery of soil functionality and nutrient cycling, we studied the development of soil phosphorus pools during Scots pine (Pinus sylvestris) revegetation in a disused sand quarry in Northwestern Russia. Sites that had been developing for different times since abandonment were compared to the parent sand and an adjacent undisturbed forest. Phosphorus speciation in genetic horizons of soil profiles was determined by sequential fractionation and solution phosphorus-31 nuclear magnetic resonance spectroscopy. Rapid transformations in soil properties occurred in 40 years, with a marked decline in pH and an accumulation of organic matter. Phosphorus transformations were shaped by geochemical processes, with a rapid release of inorganic phosphorus from primary minerals and accumulation of organic phosphorus to concentrations exceeding those found in the undisturbed site. Adsorbed and/or precipitated phosphorus increased rapidly, despite few reactive mineral colloidal surfaces. Natural succession of Scots pine in post-mining landscapes promotes ecosystem restoration through the rapid re-establishment of the biogeochemical cycles of organic matter and phosphorus. This study provides an important example of biogeochemical phosphorus cycling during the initial stages of pedogenesis.

Development and post-depositional deformation of a Middle Eocene deep-water sandy depositional system in the Sørvestsnaget Basin, SW Barents Sea

Three-dimensional seismic data from the Sørvestsnaget Basin, SW Barents Sea supported by well data, are used to investigate a Middle Eocene deep-water depositional system. The system forms a NNW-oriented sediment accumulation, characterized by increased seismic amplitudes, and abrupt western termination. The data indicate that post-depositional sand remobilization and injection led to formation of sub-circular sediment blocks up to several km wide to the east of the main accumulation. The deep-water depositional system was deformed by wing-like sandstone intrusions, extending 200–400 m upwards from the margins of the parent sand bodies. The intrusions have polygonal or broadly circular plan view geometries. Deformation is inferred to have been associated with overpressure of the sand bodies as a result of rapid burial, fluid migration into the sealed sand bodies from deeper sources via synsedimentary faults, and fluid drainage from the surrounding mudrock during early compaction. The final triggering mechanism for sand remobilization and injection is inferred to have been fracture propagation due to differential compaction and/or fault-induced earthquakes. The injectite complexes are often associated with folding of overlying strata, which we relate to differential compaction. Intrusion of sand took place during the Middle Eocene. Post-depositional sand remobilization and injection have important implications for hydrocarbon exploration because they cause changes in the reservoir primary architecture, connectivity and structure.

Origin and timing of sand injection, petroleum migration, and diagenesis in Tertiary reservoirs, south Viking Graben, North Sea

Petrographic, fluid-inclusion, and carbon and oxygen stable isotope studies of Tertiary injectite reservoirs in the south Viking Graben of the North Sea allow an understanding of the origin and timing of sand injection, petroleum migration, and diagenesis. Injection from shallowly (400 m; 1300 ft) buried Paleocene and Eocene unconsolidated sandstones occurred at the end of the Eocene, probably in response to earthquake activity. Liquid oil was already present in the parent sands prior to injection and leaked from the injectites to the seabed. Upward-migrating oil and basinal brines mixed with downward-invading mixed meteoric-marine pore fluids in the injectites, causing extensive biodegradation of the oil. Biodegradation of oil provided the driver for early carbonate cementation in injectites, causing diminished reservoir quality. However, early carbonate cementation also sealed off the injectites as potential escape routes for petroleum from the underlying parent sands. Oil (and gas) continued to migrate into the reservoir (parent) sands upon increased burial, causing a mixing of high-API oil with the early charged, extensively biodegraded low-API oil. The study of early diagenetic imprints reveals the evolution of injectite reservoirs, which forms the basis for understanding how to explore and develop them.