Lithofacies impacts on deformation bands within the Sherwood Sandstone principal aquifer

Deformation bands typically drastically reduce the permeability of sand bodies, impacting gross permeability and ultimate recovery rates for host fluids on human times-scales. This permeability reduction is important in the modelling of flow in the subsurface, and is particularly relevant in the fields of aquifer and reservoir management (hydrocarbons and water), and also in understanding the flow of contaminants through structurally deformed host-rocks. The occurrence of deformation bands is notably associated with high-porosity clastic sandstones, which on a bulk-scale often represent more porous intervals and therefore the better reservoir units in a succession, with typically elevated permeability characteristics. Here we quantitatively evaluate the likelihood of nine individual lithofacies types of aeolian or fluvial origin hosting deformation bands using exposures of the Triassic Sherwood Sandstone Group of northwest England. This study determines that of the nine lithofacies types identified the highly permeable homogeneous clean (silt/clay poor) sandstones formed by (aeolian) grainflow and grainfall processes are most prone to containing deformation bands. Genetically associated and lithologically similar interdunes are identified as the next most prevalent in hosting deformation bands despite an order of magnitude in reduction deformation band frequency. This study highlights the benefits of taking a more detailed lithofacies approach to understanding high permeability aquifers, which could lead to more effective aquifer and reservoir management for areas of the UK with the potential for multiple, conflicting use of the subsurface (e.g., groundwater, CCUS and energy storage)

Using time-series similarity measures to compare animal movement trajectories in ecology

Identifying and understanding patterns in movement data are amongst the principal aims of movement ecology. By quantifying the similarity of movement trajectories, inferences can be made about diverse processes, ranging from individual specialisation to the ontogeny of foraging strategies. Movement analysis is not unique to ecology however, and methods for estimating the similarity of movement trajectories have been developed in other fields but are currently under-utilised by ecologists. Here, we introduce five commonly used measures of trajectory similarity: dynamic time warping (DTW), longest common subsequence (LCSS), edit distance for real sequences (EDR), Fréchet distance and nearest neighbour distance (NND), of which only NND is routinely used by ecologists. We investigate the performance of each of these measures by simulating movement trajectories using an Ornstein-Uhlenbeck (OU) model in which we varied the following parameters: (1) the point of attraction, (2) the strength of attraction to this point and (3) the noise or volatility added to the movement process in order to determine which measures were most responsive to such changes. In addition, we demonstrate how these measures can be applied using movement trajectories of breeding northern gannets (Morus bassanus) by performing trajectory clustering on a large ecological dataset. Simulations showed that DTW and Fréchet distance were most responsive to changes in movement parameters and were able to distinguish between all the different parameter combinations we trialled. In contrast, NND was the least sensitive measure trialled. When applied to our gannet dataset, the five similarity measures were highly correlated despite differences in their underlying calculation. Clustering of trajectories within and across individuals allowed us to easily visualise and compare patterns of space use over time across a large dataset. Trajectory clusters reflected the bearing on which birds departed the colony and highlighted the use of well-known bathymetric features. As both the volume of movement data and the need to quantify similarity amongst animal trajectories grow, the measures described here and the bridge they provide to other fields of research will become increasingly useful in ecology

Fluid transport in the Sherwood Sandstone: influences of diagenesis and lithofacies

The Triassic age Sherwood Sandstone Group (SSG) is of great importance to the UK for several applied reasons: i) it is the lateral equivalent of the hydrocarbon producing Lower Triassic (Olenkian) Bunter Sandstone in the North Sea and the Middle Triassic (Anisian) Ormskirk Sandstone in the East Irish Sea; ii) it is a major aquifer in the UK; iii) it has storage potential for anthropogenic CO2. Increased understanding of the SSG is required to further improve efficiency of extraction, protect aquifers and reduce overall risk associated with such activities. Despite these economically important uses, the SSG has previously seen little work to ascertain any possible connections between primary sedimentological facies and diagenesis. As such, this study has analysed 30 thin sections of fluvial sandstones from 5 boreholes in and adjacent to the Needwood Basin. Using optical microscopy and scanning electron microscopy a diagenetic history was deduced and analysed with respect to sedimentological facies. The diagenetic history of the Needwood Basin SSG is comparable with the SSG from other UK sedimentary basins, with the exception of a lower quantity of well-developed authigenic quartz, feldspar and increased framework grain and cement dissolution. The results indicate that primary sedimentological facies does have a control on subsequent diagenesis. The highest porosities were found in cross bedded sandstones and massive sandstones; the lowest porosities were found in conglomerates and muddy facies; low angled cross bedded sandstones and horizontally bedded sandstones displayed a wide range of porosities. The presence of diagenetic cements had a significant effect on porosity due simply to the reduction in available pore space: calcrete or dolocrete reduced porosity on average by 17.5%, baryte by 23% and iron oxide by 8%. This data can be used to populate databases for use in fluid flow modelling to inform the hydrocarbon industry as well as hydrogeology, predictive models for contaminant transport and green technology including Carbon Capture and Storage and geothermal energy

Lithofacies control on deformation bands

Deformation bands are strain localisation features common in highly porous clastic sedimentary bodies. They form as predominately planar features with lateral extents commonly of a few metres and thicknesses frequently less than a centimetre. Deformation bands affect reservoir quality as they can have significantly reduced permeability compared to that of the host rock (typically 3-5 orders of magnitude lower). As such, the frequency and arrangement of multiple deformation bands within a reservoir sandbody can have implications for recovery rates. Despite the potential negative implications, our current ability to predict the presence of deformation bands is largely limited to their proximity to larger-scale (seismically resolvable) fault structures. However, using outcrop examples from the Triassic, aeolian-fluvial Sherwood Sandstone Group in the Cheshire Basin, this study is able to demonstrate a link between host lithofacies types and the frequency of deformation bands. Specifically, this study has shown that deformation bands are most likely to occur within the highly permeable aeolian facies types, notably grainflow and grainfall facies (constituent aeolian sand dune facies types). Deformation bands observed in aeolian facies types also have significantly larger lateral extents and are more likely to occur in complex morphologies compared to those identified in non-aeolian facies types. A new working classification scheme based on deformation band geometry is proposed that aims to provide information on the anisotropy resulting from multiple variable arrangements of deformation bands. This new scheme is complimentary to the kinematic and dominate mechanism of deformation schemes currently adopted

The influence of allogenic controls on facies variability within two basins: the Triassic Sherwood Sandstone Group of Central and Northern England

Allogenic controls (tectonics, eustasy, and climate) on sedimentation are thought to exert the most influence on depositional trends seen within sedimentary basin fill. This study examines two adjacent early Triassic basins, with similar allogenic factors of climate, eustasy and sediment supply. What is unclear is how the expression of facies/depositional trends might manifest in these two tectonically different, but otherwise similar, basins. The East Midlands shelf, is a passive shelf-edge basin marginal to the South Permian Basin. The Needwood Basin, in contrast, is a half graben created by extensional tectonics and typified by normal synsedimentary faulting. Much of the sediment supply to the basins was derived from a single sediment source (the London-Brabant High and Armorican Massif) located in present-day SE England and Northern France, with a local input to the Needwood Basin from the Pennine high. Architectural element and lithofacies analysis on three selected outcrops, and borehole logging on 8 boreholes, was conducted from across the two basins. This indicates that both basin successions comprise amalgamated channel fill, with emphasis on downstream accreting elements. In the East Midlands Shelf (Yorkshire-Nottinghamshire), the sedimentary basin infill is characterised by sandy, trough cross-bedded sequences; palaeoenvironmental interpretation suggests a sandy braided river environment. Successions from the Needwood Basin are indicative of a higher depositional energy, possibly influenced by proximity to several sources of sediment into an actively subsiding basin. Tectonic allogenic forcing factors exert a large degree of influence on depositional trends in both basins. Most notably, the degree of subsidence and distance from the basin margin is thought to have the most effect on facies type and distribution. This enhances our understanding of facies predictability and depositional trends away from data points, and can feed into the development of better reservoir models

Facies heterogeneity in the Triassic Sherwood Sandstone Group of the UK: comparing and contrasting coeval depositional basins

The primarily fluvial Triassic Sherwood Sandstone Group is found at outcrop fringing the northern part of the Needwood Basin (between Stoke-on-Trent and Nottingham) then northwards along the western margin of the East Midlands Shelf (Figure 1). The offshore lateral equivalents of the group in the East Irish Sea and North Sea (Ormskirk and Bunter sandstones) are reservoirs for oil and gas. Additionally, the Sherwood Sandstone Group is of regional importance in eastern England as the principle groundwater aquifer that supplies water for potable and industrial use. In some areas the aquifer has become contaminated by a variety of pollutants including Non-Aqueous Phase Liquids (NAPLs) and nitrates. Some pathways through the aquifer are via intergranular flow and this is partly influenced by variations in porosity and permeability, of which lithofacies is a major control. As such, further understanding of the spatial relationships between different lithofacies and associated properties at outcrop can be used to augment predictive models applicable to both the water and hydrocarbons industries. Data collection for this study focussed on 6 field localities covering the East Midlands Shelf and Needwood Basin. From these field localities numerous lithofacies have been identified and these include: i) clean homogeneous massive sandstones, ii) sandy conglomerates, iii) poorly- to moderately- sorted cross-bedded sandstones, iv) fine to very-fine cross-laminated sandstones, and v) thin horizontally laminated siltstones. Data from these field localities comprises a series of pseudo-three dimensional architectural panels which illustrate the relationship and three-dimensional configuration of observed lithofacies types. Cores from eight boreholes were also logged and provide information on the spatial distribution and relative abundance of the identified lithofacies where outcrop is sparse. This study allows a comparison of the Sherwood Sandstone Group between depocentres separated by the Charnwood palaeo-high. The dataset is being used to create qualitative and quantitative models that depict the variations in lithofacies types and configurations in the Sherwood Sandstone Group spatially; contrasting lithofacies from linked contemporaneously depositing basins. Preliminary results suggest more lateral and vertical variation in lithofacies types than has been previously described, which implies that a greater complexity of lithofacies architecture needs to be captured to improve models of fluid flow in the Sherwood Sandstone Group

Characteristics of deformation bands and relationship to primary deposition: an outcrop study from the Wirral, north-west England

The gross environment of deposition has been recognised as a major influence on the development of deformation bands. Deformation bands represent local zones of grainsize reduction/crushing and fusing that develop in response to the accommodation of stress, and typically develop in sandstones. As they can result in crosscutting planes of low permeability compared to undeformed rock, deformation bands can degrade reservoir quality, and have an adverse impact on the performance of economically important hydrocarbon reservoirs, aquifers or potential repositories for carbon capture. Outcrop of the Middle Triassic (Anisian) Sherwood Sandstone Group from Thurstaston Hill and West Kirby (Wirral, north-west England) comprises a series of stacked dune and interdune facies, with rare heterolithic fluvial associations (channel and channel lag). Aeolian dunes are characterised by relatively large-scale, low- to high-angle cross-sets with common bimodal ‘pinstripe’- type lamination, with interdunes typified by planar and ripple-laminated sandstone and silty sandstone. A striking feature is the development of deformation bands which are locally pervasive. Initial data collection shows that deformation bands are more common in grainfall and grainflow facies, becoming rare/not observed in trough, planar cross-bedded and pebbly sandstone facies. Their morphology has been categorised into 4 distinct classes based on the spatial density and relationship between individual deformation bands (see image). The permeability of these features, assessed in the field by mini-permeameter, does not appear to be related to the class of the deformation band. These features have a high permeability contrast with the surrounding sandstone, and permeability values up to two orders of magnitude lower than undeformed sandstone is indicated. Where present in reservoir rocks such as the Leman Sandstone of the North Sea, or regional aquifers such as the Wilmslow Sandstone onshore, present day bulk permeabilities may be higher in fluvial facies with no deformation bands, rather than silt and clay-poor aeolian facies that host these features. Deformation bands may have a stronger influence on fluid flow toward the end of the production history of a well or field, when reservoir pressures are depleted. These observations, could mean that reappraisal of reservoirs is required to optimise production in declining fields/aquifers

Seabird movement reveals the ecological footprint of fishing vessels.

Exploitation of the seas is currently unsustainable, with increasing demand for marine resources placing intense pressure on the Earth's largest ecosystem [1]. The scale of anthropogenic effects varies from local to entire ocean basins [1-3]. For example, discards of commercial capture fisheries can have both positive and negative impacts on scavengers at the population and community-level [2-6], although this is driven by individual foraging behaviour [3,7]. Currently, we have little understanding of the scale at which individual animals initiate such behaviours. We use the known interaction between fisheries and a wide-ranging seabird, the Northern gannet Morus bassanus[3], to investigate how fishing vessels affect individual birds' behaviours in near real-time. We document the footprint of fishing vessels' (≥15 m length) influence on foraging decisions (≤11 km), and a potential underlying behavioural mechanism, by revealing how birds respond differently to vessels depending on gear type and activity. Such influences have important implications for fisheries, including the proposed discard ban [8]), and wider marine management

Frequency and consequences of individual dietary specialisation in a wide-ranging marine predator, the northern gannet

Individual specialisations in animals are important contributors to a wide range of ecological and evolutionary processes, and have been particularly documented in relation to multiple aspects of foraging behaviours. Central-place foragers, such as seabirds, frequently exhibit pronounced specialisations and individual differences in a variety of foraging traits. In particular, the availability of fisheries discards alongside natural prey resources provides additional potential for differentiation and specialisation for opportunistically scavenging seabird species. However, the consequences of such specialisations for at-sea distributions and intraspecific interactions are not well known. Here, we investigated the links between the degree of dietary specialisation on natural or discarded prey and the foraging movements and spatial occupancy of northern gannets Morus bassanus in relation to differing intraspecific competition at 6 colonies of differing sizes. We found that, at most colonies, individuals with different dietary strategies concentrated foraging at differing levels of intraspecific competition. In addition, individuals pursuing different strategies were frequently, but not consistently, spatially separated, distinctions that were most acutely seen in females. However, this variation in individual strategy had no significant impact on current body condition. These analyses demonstrate how foraging-associated metrics need not covary within an unconstrained system. They also reveal that specialisation can have important consequences for the competitive regimes individuals experience, highlighting the complexity of examining interacting consequences at large spatial scales

A Perspective of Coagulation Dysfunction in Multiple Sclerosis and in Experimental Allergic Encephalomyelitis

A key role of both coagulation and vascular thrombosis has been reported since the first descriptions of multiple sclerosis (MS). Subsequently, the observation of a close concordance between perivascular fibrin(ogen) deposition and the occurrence of clinical signs in experimental allergic encephalomyelitis (EAE), an animal model of MS, led to numerous investigations focused on the role of thrombin and fibrin(ogen). Indeed, the activation of microglia, resident innate immune cells, occurs early after fibrinogen leakage in the pre-demyelinating lesion stage of EAE and MS. Thrombin has both neuroprotective and pro-apoptotic effects according to its concentration. After exposure to high concentrations of thrombin, astrocytes become reactive and lose their neuroprotective and supportive functions, microglia proliferate, and produce reactive oxygen species, IL-1β, and TNFα. Heparin inhibits the thrombin generation and suppresses EAE. Platelets play an important role too. Indeed, in the acute phase of the disease, they begin the inflammatory response in the central nervous system by producing of IL-1alpha and triggering and amplifying the immune response. Their depletion, on the contrary, ameliorates the course of EAE. Finally, it has been proven that the use of several anticoagulant agents can successfully improve EAE. Altogether, these studies highlight the role of the coagulation pathway in the pathophysiology of MS and suggest possible therapeutic targets that may complement existing treatments