Total organic carbon in the Bowland-Hodder Unit of the southern Widmerpool Gulf: a discussion

This review of the article by Kenomore et al. (2017) on the total organic carbon (TOC) evaluation of the Bowland Shale Formation in the Widmerpool Gulf sub-basin (southern Pennine Basin, UK) reveals a number of deficiencies, rooted mostly in an inadequate appreciation of the local Carboniferous stratigraphy. Kenomore et al. use the ΔLog R, the ‘Passey’ method after Passey et al. (1990), to evaluate the TOC content in two boreholes in the Widmerpool Gulf: Rempstone 1 and Old Dalby 1. We show here that Kenomore and co-authors used maturity data, published by Andrews (2013), from different formations to calibrate their TOC models of the Bowland Shale Formation (Late Mississippian–Early Pennsylvanian); the Morridge Formation in Rempstone 1 and the Widmerpool Formation in Old Dalby 1. We contest that this gives viable TOC estimates for the Bowland Shale Formation and that because of the location of the boreholes these TOC models are not representative over the whole of the Widmerpool Gulf. The pyrite content of the mudstones in the Widmerpool Gulf also surpasses the threshold where it becomes an influence on geophysical well logs. Aside from these stratigraphic and lithologic issues, some methodological weaknesses were not adequately resolved by Kenomore and co-authors. No lithological information is available for the Rock-Eval samples used for the maturity calibration, which because of the interbedded nature of the source formations has implications for the modelling exercise. We recommend that more geochemical data from a larger array of boreholes covering a wider area, proximal and distal, of the basin are collected before any inferences on TOC are made. This is necessary in the complex Bowland Shale system where lithological changes occur on a centimetre scale and correlations between the different sub basins are not well understood

Quantitative palynological analysis of the E2a and E2b goniatite biozones (Arnsbergian, Mississippian) in mudstones from the Southern Pennine Basin (U.K.)

We performed a quantitative palynological analysis of Arnsbergian (Namurian, Late Mississippian) mudstone intervals, potentially prospective for unconventional hydrocarbons. While many palynological studies exist on these stratigraphic intervals in the Widmerpool Gulf and the Edale Basin (sub-basins of the Pennine Basin), very few studies perform full statistical analyses. Using the Carsington Dam Reconstruction C3 (Carsington DRC3, Widmerpool Gulf) and the Karenight-1 (Edale Basin) boreholes, we show that the combination of quantitative palynological data and detrended correspondence analysis (DCA) can aid biozonation and additionally, provide paleoecological constraints to the Arnsbergian mudrocks. The studied interval in Carsington DRC3 was assigned to the TK miospore biozone and a hitherto undescribed peak in the fresh water alga Botryococcus was recorded. Using relative abundances of hinterland species, mainly from the genus Florinites, both boreholes could be correlated and a more confident assignment of the TK miospore biozone covering an interval containing goniatite biozone E2b in Karenight-1 was achieved. The techniques used in the current study should be especially valuable for assessing borehole materials where the recovery of macrofossils, like goniatites used as the main biostratigraphic tool in the Namurian, can be very low. Future studies should focus on the same stratigraphic interval from different sub-basins of the Pennine Basin to further assess the applicability of quantitative palynological analysis combined with DCA as a stratigraphic tool for potentially prospective mudstones

Taxonomy online 3 : the 'Bernard Owens Collection' of single grain mount palynological slides : Carboniferous pollen and spores part II

The Bernard Owens Collection comprises single grain mounts of some 145, mostly Palaeozoic, miospore and pollen taxa, each represented by many specimens displaying the most diagnostic features of the original holotype diagnosis and a wide range of preservation states and natural morphological variations. It is very likely the most important collection of single grain, Late Palaeozoic palynomorphs. The specimens were collected worldwide but because Bernard’s studies laid the foundation of the Carboniferous miospore biozonation across Western Europe (e.g. Clayton et al., 1977; McLean et al., 2018; Owens et al., 1978; Owens et al., 2004; Owens et al., 2005; Owens et al., 1977), examples of the Carboniferous in the UK and mainland Europe form the bulk of the source material of the palynomorphs discussed in the rest of this report. This is the second report describing the Bernard Owens Collection, following Stephenson and Owens (2006)

Northern Hemisphere Glaciation during the Globally Warm Early Late Pliocene

The early Late Pliocene (3.6 to ~3.0 million years ago) is the last extended interval in Earth's history when atmospheric CO2 concentrations were comparable to today's and global climate was warmer. Yet a severe global glaciation during marine isotope stage (MIS) M2 interrupted this phase of global warmth ~3.30 million years ago, and is seen as a premature attempt of the climate system to establish an ice-age world. Here we propose a conceptual model for the glaciation and deglaciation of MIS M2 based on geochemical and palynological records from five marine sediment cores along a Caribbean to eastern North Atlantic transect. Our records show that increased Pacific-to-Atlantic flow via the Central American Seaway weakened the North Atlantic Current and attendant northward heat transport prior to MIS M2. The consequent cooling of the northern high latitude oceans permitted expansion of the continental ice sheets during MIS M2, despite near-modern atmospheric CO2 concentrations. Sea level drop during this glaciation halted the inflow of Pacific water to the Atlantic via the Central American Seaway, allowing the build-up of a Caribbean Warm Pool. Once this warm pool was large enough, the Gulf Stream–North Atlantic Current system was reinvigorated, leading to significant northward heat transport that terminated the glaciation. Before and after MIS M2, heat transport via the North Atlantic Current was crucial in maintaining warm climates comparable to those predicted for the end of this century

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

Geochemical element mobilisation by interaction of Bowland shale with acidic fluids

Hydraulic fracturing is widely used to exploit unconventional hydrocarbon sources, to enhance exploitation of geothermal energy and to aid in carbon sequestration through underground storage of captured . The hydraulic fracturing fluids, which are commonly acidic, cause dissolution of minerals and desorption of elements which can lead to groundwater contamination. Batch reactor experiments were conducted to explore the interaction of simulated fracturing fluids with two end member compositions of basinal shales of the Bowland-Hodder unit (Carboniferous, UK) whereby the impact of temperature, fluid acidity, and rock/fluid ratio conditions were investigated. The results demonstrate that the fluid acidity is mainly controlled by the oxidative dissolution of pyrite and the dissolution of calcite, impacting mobilisation and fate of major and trace elements. The dissolution of calcite and pyrite significantly dominates the leaching of Sr and As, respectively. Generally, increased fluid acidity and temperature facilitate element mobilisation due to enhanced mineral dissolution and ion desorption, whereas higher rock/fluid ratio (higher mass of carbonate minerals) raises the buffering capacity and may promote the immobilisation of some metal ions by adsorption and precipitation (e.g. Ba, Pb, Fe, Al, and Mn). Moreover, the surface topography of different minerals in polished shale sample sections after fluid-rock interaction indicates that mineralogical compositions may play an important role in determining the pore structure. This research identifies chemical reaction pathways of geochemical elements (including contaminants) in fracturing fluids over a range of fluid chemistries and environmental conditions, and helps to evaluate element mobilisation from shale reservoirs with differing mineralogies

Can One-Run-Fixed-Arrhenius Kerogen Analysis Provide Comparable Organofacies Results to Detailed Palynological Analysis? A Case Study from a Prospective Mississippian Source Rock Reservoir (Bowland Shale, UK)

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 ( 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

Impacts of regional allogenic forcing on a single depositional system: example from the Sherwood Sandstone Group, UK.

The Triassic Sherwood Sandstone Group offers an opportunity to study outcrop and borehole sections through a dryland fluvial system whose lateral correlatives are exploited for hydrocarbons and groundwater; it also suffers contamination from a legacy of industrialisation over the past 250+ years. A detailed understanding of flow, and processes that influence flow through this rock unit is therefore relevant to the development of reservoir and contaminant management strategies. This study assesses five regions which, as a result of allogenic forcing, show variations in the lithofacies architecture and arrangement at both regional and local scales. This includes thicker successions of clean sandstones with isolated mudstone lenses, to condensed successions of gravelly sandstone largely devoid of mudstone. Most allogenic forcing is likely to be syn-sedimentary; however, subtle variations in facies are demonstrated to have a major influence in diagenetic processes, including the development of deformation bands and cementation. Whilst these occurred exclusively post-depositionally, they are also responsible for marked reductions in the host facies permeability within the Group. These variations in lithological and property heterogeneity within the Sherwood Sandstone Group ultimately affect its ability to store and transport fluids. A series of regional models are depicted that show the relative challenges associated with the each regions unique mix of autogenic and allogenic controls. These diagrams are placed within a matrix that allows prediction of sedimentary architecture based on the presence/absence of a variety of allogenic controls. Data collection for this work comprises borehole records and outcrop studies (architectural panelling and sedimentary logging), which provide a useful dataset that places diagenetic processes including the formation and style of deformation band in context, and also illustrates the facies architecture of this critical geological horizon in the UK

Dinoflagellate cyst paleoecology during the Pliocene–Pleistocene climatic transition in the North Atlantic

Dinoflagellate cysts (dinocysts) are widely used as tracers of sea surface conditions in late Quaternary marine records. However, paleoenvironmental reconstructions across the Pliocene–Pleistocene climatic transition and beyond are limited because the hydrologic conditions influencing assemblage compositions may not have a modern analogue, and the ecological optima of extinct dinocyst species are not well known. From a study of two cored sites in the central and eastern North Atlantic, we bypass these issues by statistically analyzing the variations in dinocyst assemblage composition and comparing the results directly to paleoecological parameters (δ18Obulloides, δ18Osalinity, and geochemical proxies for sea surface temperature [SST]) derived from the planktonic foraminifer Globigerina bulloides recovered from the same samples as the dinocysts. Through canonical correspondence analysis we demonstrate the co-variation of seasonality and dinocyst paleoproductivity. We show that Pyxidinopsis braboi is a cold tolerant species with an optimum SST between 12 and 14 °C. We extend the use of Nematosphaeropsis labyrinthus as an indicator of transitional climatic conditions to the Pliocene, we offer evidence for the correlation of Bitectatodinium tepikiense and Filisphaera microornata to high seasonality, and we reiterate an apparent link between Spiniferites mirabilis and eastern North Atlantic water masses. Finally, we confirm that Habibacysta tectata is cold-tolerant rather than a strictly cold-water indicator, that Operculodinium? eirikianum is a cold-intolerant species favoring outer neritic environments, and that Ataxiodinium confusum and Invertocysta lacrymosa are both warm-water species

Long-term methylphenidate exposure and 24-hours blood pressure and left ventricular mass in adolescents and young adults with attention deficit hyperactivity disorder

Blood pressure; Echocardiography; MethylphenidatePresión arterial; Ecocardiografía; MetilfenidatoPressió arterial; Ecocardiografia; MetilfenidatYoung people with attention deficit hyperactivity disorder (ADHD) are now being treated with psychostimulant medication for longer than was previously the case and are increasingly likely to remain on methylphenidate into adolescence and adulthood. This study was designed to determine whether the long-term use of methylphenidate (MPH, immediate release or extended release) increases blood pressure and left ventricular mass (LVM) identified by echocardiography in adolescents and young adults with ADHD aged 12-25 years. In a five-site cross-sectional design two groups were compared for 24- hour blood pressure and heart rate (HR) registrations and LVM: 1) adolescents and young adults with ADHD who had been treated with MPH for > 2 years (N=162, age mean (SD) 15.6 (3.0)), and 2) adolescents and young adults with ADHD who had never been treated with methylphenidate (N=71, age mean 17.4 (4.2)). The analyses were controlled for propensity scores derived from age, sex, height, weight, and 19 relevant background variables. A blood pressure indicative of hypertension (>95th percentile) was observed in 12.2% (95% confidence interval 7.3 – 18.9%) of the participants in the MPH treated group and in 9.6% (95%CI 3.2 – 21.0%) of the MPH naïve group, with overlapping intervals. The 24-hour recorded systolic blood pressure (SBP) and HR were significantly higher during daytime in medicated individuals with ADHD than in those with unmedicated ADHD, but were similar in both groups during the night. 24-hour diastolic blood pressure (DBP) did not differ between both groups during either daytime or at night. LVM, corrected for body-surface area (LVMBSA), also did not differ between the two groups (p=0.20, controlling for confounders). Further, MPH daily dose and duration of treatment were unrelated to LVMBSA, SBP, and DBP. Long-term MPH use in adolescents and young adults with ADHD is associated with small but significant increases of SBP and HR during daytime. Given the current sample size, the proportions of hypertension do not differ significantly between MPH treated and MPH-naïve individuals with ADHD. Future studies with larger samples, longer treatment duration, and/or with within-subject designs are necessary. The results do, however, further support recommendations that highlight the importance of monitoring blood pressure and HR during MPH treatment.This work was supported by the European Union 7th framework grant “Attention Deficit Hyperactivity Disorder Drugs Use Chronic Effects” (ADDUCE, grant no. 260576). The funder had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results. Any views expressed are those of the authors and not necessarily those of the funder