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Foundational uncertainties in terminal Ediacaran chronostratigraphy revealed by high-precision zircon U-Pb geochronology of the Nama Group, Namibia
No full textThe Nama Group of southern Namibia and northwestern South Africa hosts the best-dated mixed carbonate-siliciclastic foreland basin succession of the terminal Ediacaran [ca. 551 million years (Ma) ago to <538 Ma] and is key for resolving the chronology of early metazoan evolution. Numerous silicified volcanic tuff interbeds are present, but differing interpretations regarding the fidelity of their ages lead to different regional stratigraphic correlations, especially for the Urusis Formation of the Schwarzrand Subgroup. An expanded record of the Urusis Formation is found in the Swartpunt area of southern Namibia, which has yielded an important metazoan biota. But the succession in this area is preserved as a series of thrusts at the leading edge of the Gariep orogenic belt and zircon U-Pb data show systematic age repetition. We use regional stratigraphic and structural mapping, integrated with carbonate carbon isotope (δ13Ccarb) chemostratigraphy and high-precision radioisotope U-Pb zircon geochronology from outcrop and recently acquired drill core to develop a temporally calibrated basin-wide depositional model. This integrated dataset either reflects complex zircon reworking, inheritance, or potential analytical biases (Scenario 1) or the presence of a Gariep-related cryptic décollement within the Spitskop Member that has resulted in stratigraphic repetition (Scenario 2). We investigate the evidence for and against both scenarios and consider their implications for stratigraphic and δ13Ccarb correlations between the Swartpunt area and coeval exposures along the Orange River border with South Africa.
Given that these issues are in an area that hosts numerous silicified ash beds and extensive exposure, an inability to confidently discount either scenario highlights a level of compounding uncertainty in zircon U-Pb geochronology that must be considered when attempting to build global chronostratigraphic frameworks. Scenario 1 implies that some of the weighted mean ages and Bayesian eruption ages from the Swartpunt area may be >1 Myr older than the depositional age of their respective ash beds when assuming existing stratigraphic correlations. If this scenario is preferred, then a cautious approach would be to consider all weighted mean zircon U-Pb ages from ash beds to reflect maximum depositional ages. Both scenarios support deposition of the Huns Member >540 Ma in the Swartpunt area if the oldest weighted mean age reported here represents a near-depositional age, which has significant implications for the temporal calibration of important terminal Ediacaran ichnofossil assemblages and future cyclostratigraphic studies.
Stratigraphic correlations common to both scenarios allow us to temporally calibrate a basin evolution model for the Nama Group. Temporal trends in initial hafnium isotope (εHf) compositions of zircon grains from ash beds throughout the succession may support progressive crustal thickening associated with underplating of the Damara orogenic belt along the northern periphery of the Kalahari craton from ca. 547 Ma to ca. 538 Ma. The compilation of new and published zircon U-Pb ages may also imply that the locus of carbonate platform development migrated from north to south (present co-ordinates), tracking the migration of foredeep subsidence
Ediacaran-Cambrian Boundary in the Anti-Atlas belt (Morocco): A review of biostratigraphy, chemostratigraphy and geochronology
No full textThe Ediacaran-Cambrian transition represents a pivotal geological marker, denoting the decline of the Ediacaran biota and the emergence of most modern phyla in an interval marked by perturbations to the carbon cycle (as evidence by carbonate carbon isotopes, δ13Ccarb), biotic turnover, dynamic paleoredox regimes, and magnetic field instability. Following initial international expeditions to the Anti-Atlas belt in Morocco, numerous attempts have sought to pinpoint the exact stratigraphic level of the Ediacaran-Cambrian boundary (E-C) in this important succession, where ca. 3 km of continuous carbonate rocks provide one of the most complete successions for the establishment of a global δ13Ccarb chemostratigraphic reference curve. Subsequently, a growing number of publications have explored the stratigraphy, paleontology, and geochronology of the Ediacaran-Cambrian transition in the Anti-Atlas. Despite extensive efforts, the precise position of the E-C boundary in the Anti-Atlas remains ambiguous, with multiple proposed positions ranging from within the Ouarzazate Group to the lower part of the Tifnout Member (Adoudou Formation, Taroudant Group). Here, we conduct a comprehensive review of the available chemostratigraphic, paleontological, and geochronological data associated with the late Ediacaran-Cambrian Ouarzazate Group and Adoudou Formation within the Anti-Atlas belt. The objective is to refine our understanding of the regional expression of the E-C boundary and offer clarity on the inconsistencies observed among biostratigraphy, chemostratigraphy, and geochronology. This review underscores that the currently proposed boundary relies primarily on the δ13Ccarb excursion, lacking corroboration from other independent markers such as geochronology and globally significant ichnofossil assemblage constituents. Additionally, through the integration of newly available data and enhanced global chemostratigraphy, biostratigraphy, and geochronology, our findings suggest that the E-C boundary within the Western Anti-Atlas may be positioned as low as within the upper unit of the Tabia Member. However, this interpretation relies heavily on a Fortunian age for the ichnotaxa Monomorphichnus, in the absence of co-occurring specimens of the boundary-defining ichnospecies Treptichnus pedum. Moreover, a revised assessment of chemostratigraphic correlation and geochronological markers indicates that the Tabia and Tifnout members in the Central and Eastern Anti-Atlas do not correlate with the same named members in the Western Anti-Atlas. Both the Tabia and Tifnout members of the Central-Eastern Anti-Atlas may instead correlate with the middle part of Tifnout Member in the Western Anti-Atlas. This implies a late Ediacaran to early Cambrian ca. 10 m.y stratigraphic gap in the Central-Eastern Anti-Atlas and hence the E-C boundary in the Central-Eastern Anti-Atlas is likely situated within the unconformity between the Ouarzazate and Taroudant Groups. Lastly, we present unresolved questions regarding the biogenicity and affinities of some described discoidal structures and calcified microfossils from the Tabia Member, with the aim of further stimulating active engagement of the global scientific community in the establishment of robust paleontological and chronostratigraphic constraints for the E-C boundary within the Anti-Atlas belt
The past, present and future of observations of externally irradiated disks
No full textRecent years have seen a surge of interest in the community studying the effect of ultraviolet radiation environment, predominantly set by OB stars, on protoplanetary disc evolution and planet formation. This is important because a significant fraction of planetary systems, potentially including our own, formed in close proximity to OB stars. This is a rapidly developing field, with a broad range of observations across many regions recently obtained or recently scheduled. In this paper, stimulated by a series of workshops on the topic, we take stock of the current and upcoming observations. We discuss how the community can build on this recent success with future observations to make progress in answering the big questions of the field, with the broad goal of disentangling how external photoevaporation contributes to shaping the observed (exo)planet population. Both existing and future instruments offer numerous opportunities to make progress towards this goal
Age at arrival and immigrants’ housing outcomes: evidence from the UK
No full textWe provide new evidence on how immigrants' age at arrival relates to their housing tenure and living conditions in the UK. While previous research has examined the role of socio-economic and demographic factors in immigrants' housing outcomes, the effect of age at migration remains underexplored. Using a representative dataset from the UK Household Longitudinal Study, we analyse how immigrants' arrival age is associated with their likelihood of homeownership, reliance on social housing, and housing quality. Our findings confirm that those who arrive as adults face significantly lower homeownership prospects than those who arrive aged 0-5 years, with the oldest arrivals exhibiting a 44-percentage-point gap. Contrary to expectations, later arrivals are not more likely to rely on social housing than earlier arrivals or natives. Furthermore, we find no strong evidence that housing or neighbourhood quality differs systematically based on age at arrival. These results provide insight into the link between immigrant generations, housing market segments and housing quality outcomes with implications for household welfare. The findings are therefore relevant for policymakers and valuable for local and regional expenditure, forecasting, and economic development
Data-driven prediction of daily Cryptosporidium river concentrations for water resource management: use of catchment-averaged vs spatially distributed features in a Bagging-XGBoost model
No full textCryptosporidium is a waterborne pathogen which poses a major challenge to water utilities because of its resistance to chlorination and its infectivity at very low concentrations. The ability to make predictions of Cryptosporidium concentrations in rivers would aid significantly in abstraction-based risk management of water resources, but current models are inappropriate for making predictions at the temporal resolutions required to inform abstraction decision-making. This study utilises Cryptosporidium data collected over 7 years at a major river abstraction site in South East England, alongside publicly-available remote sensing data, to train a Bagging-XGBoost model for Cryptosporidium predictive applications at daily timescales. Different combinations of catchment-averaged and spatially distributed datasets were trialled as model inputs. The highest-performing models predicted 69–75 % of >1 oocysts L−1 exceedances, and they also predicted the timing of 78–89 % of higher (>2 oocysts L−1) exceedances. Interpretation of predictions using SHapley Additive exPlanations analysis indicated that sources near (<30 km) to the intake were the most important and identified catchment-averaged rainfall at 1 and 2-day lag time and antecedent Cryptosporidium measurements as significant inputs. The study demonstrates the potential of such models when an unparsimonious approach to feature selection is taken, because of their ability to discern non-linear trends and their resistance to multicollinearity and redundancy in the input data. Such models could improve the ability of water utilities to predict Cryptosporidium peaks and aid abstraction decision-making, thereby reducing the loadings of this pathogen to reservoirs and water treatment works
To Determine if Changing to White Light Street Lamps Reduces Crime: A Multilevel Longitudinal Analysis of Crime Occurrence during the Relighting of Leeds, a UK City
No full textThis confirmatory study estimates the effect on Police Recorded Crimes (PRCs) of a relighting programme that installed nearly 80,000 white-light lamps, replacing predominantly orange ones, in the years 2005 to 2013, throughout the UK city of Leeds. Time series of weekly PRCs in all 107 Middle-layer Super Output Areas, while road lighting was being almost completely relit, were analysed using multilevel modelling. The background change in PRCs in each area, when and where no lighting was changed, was separated from that associated with when and where replacement white lamps were installed, by including a polynomial for the underlying time-trend. The key interest is how the replacement by new white lamps affects the rate of crime, from the start to the finish of the relighting. The results show that over the period, there was an estimated 2% rise in daylight adjusted darkness crime associated with relighting, 95% confidence interval (CI) (−3% to +7%). Similarly associated with relighting, (unadjusted) darkness crime showed a rise of 3%, 95% CI (−1% to +8%) and the round-the-clock measure of crime (the sum of darkness and daylight crime) gave an estimated rise of 3%, 95% CI (0% to +6%). Many checks were made, all giving consistent null results; that is, giving narrow confidence intervals around zero of only a few percent wide after relighting. Therefore, no evidence was found for an improvement (or detriment) in the city’s level of crime by relighting, contrary to the substantial reduction anticipated by the city council
Training DAFNEplus facilitators in novel behaviour change approaches: a template for training design and delivery
No full textBackground
The integration of behaviour change principles into diabetes structured education programmes is key to sustaining long-term improvements in glycaemic management. Good quality training for diabetes educators that enables them to understand and feel confident in behaviour change approaches, is fundamental to their delivery. Educator training programmes are rarely described in detail despite this information being needed to enable interpretation of trial/outcome data, fidelity analyses and replicability between centres.
Aims
This paper presents an overview of a bespoke training programme developed for educators who delivered the DAFNEplus programme. DAFNEplus is a revised version of the Dose Adjustment for Normal Eating Programme (DAFNE) for people with type 1 diabetes. The revisions incorporate novel technology, behaviour change approaches and structured individualised follow-up.
Materials and Methods
This paper outlines the structure of the training provided to educators, a summary of its development and examples of training content and process.
Results
We provide a template for future training courses, where psychological approaches are integrated into standard diabetes education and delivered by healthcare professionals.
Discussion
The impact upon educators' perceptions and delivery of structured education, as well as the potential for ongoing training development, is also discussed
The politics of restoration playbook dedications
No full textThe dedications to Restoration play quartos were an important part of what readers could expect to find when they picked up a late seventeenth-century playbook. Addressed to aristocrats, celebrities, politicians, and other leading figures of the day, the printed play dedication has been read by later generations of historians and literary scholars as one of the surest means we have of decoding the politics and ideological investments of Restoration dramatists and their works. This article revisits and overturns this assumption by arguing instead that Restoration playbook dedications and their politics need to be read in dialogue with the commercial pressures of contemporary book-trade practices. I argue that the politics of playbooks were inextricable from print marketplace concerns by combining quantitative and qualitative analysis of the dedications produced during the Exclusion Crisis (1679–81) with a closely contextualised analysis of Jacob Tonson's quarto edition of Aphra Behn's The Second Part of the Rover (1681)
What workers want: Conditions for a fair and just transition in the UK
No full textThere is cynicism amongst UK workers that the transition to a low carbon economy will lead to high quality, local jobs, with over a third considering local job losses likely.
There is a threefold need for managed decarbonisation: to meet national emissions targets, to mitigate against political backlash, andto revitalise local and regional economies. The complexity of realising the low carbon transitionand its potential risks to employment highlight the importance of including workers and their representatives in planning.
This briefing synthesises wide-ranging research from the Centre for Employment Relations, Innovation and Change (CERIC) which points to conditions for a low carbon transition, from the perspectives of both workers and those who represent them. We recommend that the UK government learns from international example to ensure oversight and fairness in the transition and
reap the co-benefits that a managed transition can provide.