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The first record of the Early Toarcian Oceanic Anoxic Event (c. 183 Ma) from the Southern Hemisphere is described from the Neuquen Basin, Argentina, identified chemostratigraphically on the basis of a relative increase in marine organic carbon and a characteristic negative carbon-isotope excursion ([[delta].sup.13][C.sub.org]) in bulk rock and fossil wood. The negative excursion of -6 [per thousand] in bulk organic carbon (falling to -31.3 [per thousand]) crosses the boundary of the tenuicostatum--hoelderi Andean ammonite Zones, equivalent to the tenuicostatum--falciferum/serpentinum zones of Europe. These data indicate that the Early Toarcian Oceanic Anoxic Event was a global phenomenon. Supplementary material: A detailed stratigraphic log, chemostratigraphic data and nannofossil data are available at http:// www.geolsoc.org.uk/SUP18411. doi: 10.1144/0016-76492010-025.

Micropalaeontological and chemostratigraphic results from the mid-Cretaceous 'upper siliceous zone' of the Ionian zone, studied in two localities of NW Greece (Paliambela and Panaya), provide new insights into the palaeoceanographic evolution of Tethys and better correlation with well-studied Italian successions. [[delta].sup.13]C carbonate and organic-carbon isotope stratigraphy allows an improved correlation of the early Aptian Fourcade Level with Oceanic Anoxic Event 1a. Calcareous nannofossils point to intervals of reduced sedimentation within the late Aptian part of the limestones overlying the Fourcade Level. Combined calcareous nannofossil, radiolarian and planktonic foraminiferal biostratigraphy suggests that the overlying radiolarites (named herein the 'Dercourt Member') are essentially mid-Albian in age. Radiolarites of this age and thickness have not been identified in the well-explored Italian sections of in southern Albania. It is therefore likely that the Dercourt radiolarites reflect a high-productivity event localized in the Greek area of the Ionian zone, possibly caused by a bathymetrically induced upwelling of intermediate to deep waters that entered the Ionian trough following the opening of new oceanic gateways in the Eastern Mediterranean Tethys. Keywords: Ionian zone, Cretaceous, palaeoceanography, chemostratigraphy, micropalaeontology.

Widespread marine anoxia triggered by the runoff and recycling of nutrients was a key phenomenon associated with the Frasnian–Famennian (FF) mass extinction. However, the relative importance of global‐scale processes versus local influences on site‐specific environmental change remains poorly understood. Here, nitrogen‐isotope (δ15N) trends are combined with organic‐biomarker, phosphorus, and Rock‐Eval data in FF sites from the USA (H‐32 core, Iowa), Poland (Kowala Quarry), and Belgium (Sinsin). Up‐to‐date cyclostratigraphic age models for all three sites allow the nature and timing of changes to be precisely compared across the globe. Negative δ15N excursions across the FF interval from the H‐32 core and Kowala correlate with geochemical evidence for euxinic, phosphorus‐rich, water columns, and possible cyanobacterial activity, suggestive of increased diazotrophic N fixation, potentially coupled with ammonium assimilation at the latter site. By contrast, previously studied sites from Western Canada and South China document enhanced water‐column denitrification around the onset of the Upper Kellwasser (UKW) Event, re‐emphasizing the geographical heterogeneity in environmental perturbations at that time. Moreover, environmental degradation began >100 kyr earlier in Poland, coeval with a major increase in bioavailable phosphorus supply, than in Iowa, where no such influx is recorded. These regional differences in both the timing and nature of marine perturbations during the FF interval likely resulted from the variable influx of terrigenous nutrients to different marine basins at that time, highlighting the importance of local processes such as terrestrial runoff in driving environmental degradation during times of climate cooling such as the UKW Event. Plain Language Summary: The Frasnian–Famennian mass extinction, ∼372 million years ago, marked one of the most severe biological crises in Earth's history. The extinction has been linked to rapid climate changes and reduced seawater oxygen levels across the global ocean. However, the degree to which environmental stress was globally versus locally controlled remains unclear. This study presents geochemical markers of water‐column oxygenation and nutrient cycling (nitrogen isotopes, phosphorus contents, organic biomarkers) at three localities, the H‐32 core (Iowa, USA), the Kowala Quarry (Poland), and Sinsin (Belgium). The unique feature of these records is the existence of precise age‐depth models, allowing direct comparison of the timing of environmental changes between these sites, and with other key sections from Western Canada and South China. It is shown that whilst the H‐32 core and Kowala indicate possible increases in cyanobacterial nitrogen fixation under phosphorus‐rich, oxygen‐ and nitrate‐depleted conditions, other sites show markedly different nitrogen‐cycle disturbances, such as enhanced water‐column denitrification. Additionally, environmental stress commenced earlier in Kowala than elsewhere, coincident with elevated phosphorus influx to that setting. These regional variations in the timing and nature of environmental perturbations emphasize the importance of local processes such as terrestrial nutrient runoff in causing the Frasnian–Famennian extinction. Key Points: Nitrogen‐isotope records of globally variable environmental change in the Frasnian–Famennian crisisCombination with age models highlights further variability in the onset of those changesMulti‐proxy geochemistry highlights nutrient runoff as trigger of earliest anoxia [ABSTRACT FROM AUTHOR]

The Mesozoic witnessed some episodes of marked accumulation and burial of organic matter (OM) in the Tethys Ocean and satellite basins, such as the Vocontian Basin (SE-France). These famous episodes, termed Oceanic Anoxic Events (OAEs), resulted from various factors, acting in complex synergies; the consensus about the key factors has not been reached yet. The Aptian–Albian Blue Marls Formation (Fm.) of the Vocontian Basin recorded the various substages of OAE1, plus additional organic-rich levels of regional extension. The semi-pelagic marlstones of the Blue Marls Fm. allow to carry out a detailed examination of the molecular fossils, to assess the respective weights of the factors involved in the OM storage process. In this work, we examined the lipid biomarkers of six organic-rich levels ranging from the Goguel Level to the Paquier Level in stratigraphic order. Biomarkers reputed to be characteristic of some OAEs are observed here: 2-methylhopanoids in the Goguel Level (OAE1a) and archaeal lipids in the Jacob, Kilian and Paquier Levels (OAE1b). This study shows that, in the Vocontian Basin, OM deposition resulted mostly from local factors and that each level has its own peculiarities; however, overarching connections with the Tethys Ocean were critical for the recording of global anoxic events.

Summary: Thermococcales, a major order of archaea inhabiting the iron‐ and sulfur‐rich anaerobic parts of hydrothermal deep‐sea vents, have been shown to rapidly produce abundant quantities of pyrite FeS2 in iron–sulfur‐rich fluids at 85°C, suggesting that they may contribute to the formation of 'low temperature' FeS2 in their ecosystem. We show that this process operates in Thermococcus kodakarensis only when zero‐valent sulfur is directly available as intracellular sulfur vesicles. Whether in the presence or absence of zero‐valent sulfur, significant amounts of Fe3S4 greigite nanocrystals are formed extracellularly. We also show that mineralization of iron sulfides induces massive cell mortality but that concomitantly with the formation of greigite and/or pyrite, a new generation of cells can grow. This phenomenon is observed for Fe concentrations of 5 mM but not higher suggesting that above a threshold in the iron pulse all cells are lysed. We hypothesize that iron sulfides precipitation on former cell materials might induce the release of nutrients in the mineralization medium further used by a fraction of surviving non‐mineralized cells allowing production of new alive cells. This suggests that biologically induced mineralization of iron‐sulfides could be part of a survival strategy employed by Thermococcales to cope with mineralizing high‐temperature hydrothermal environments. [ABSTRACT FROM AUTHOR]

Solar analogues are important stars to study for understanding the properties of the Sun. Combined with seismic and spectroscopic analysis, evolutionary modelling becomes a powerful method to characterize stellar intrinsic parameters, such as mass, radius, metallicity and age. However, these characteristics, relevant for other aspects of astrophysics or exoplanetary system physics, for example, are difficult to obtain with high precision and/or accuracy. The goal of this study is to characterize the two solar analogues, HD 42618 and HD 43587, observed by CoRoT. In particular, we aim to infer their precise mass, radius and age, using evolutionary modelling constrained by spectroscopic, photometric and seismic analysis. These stars show evidence of being older than the Sun but with a relatively large lithium abundance. We present the seismic analysis of HD 42618, and the modelling of the two solar analogues, HD 42618 and HD 43587 using the cestam stellar evolution code. Models were computed to reproduce the spectroscopic (effective temperature and metallicity) and seismic (mode frequency) data, and the luminosity of the stars, based on Gaia parallaxes. We infer very similar values of mass and radius for both stars compared with the literature, within the uncertainties, and we reproduce correctly the seismic constraints. The modelling shows that HD 42618 is slightly less massive and older than the Sun, and that HD 43587 is more massive and older than the Sun, in agreement with previous results. The use of chemical clocks improves the reliability of our age estimates. [ABSTRACT FROM AUTHOR]

This work examines the possibility of a rapid formation of glauconite in a relatively shallow platform environment (below fair-weather wave baseline). The materials studied here are uppermost Jurassic alternations of carbonate beds and marly interbeds, namely, the Assises de Croï Formation of the Boulonnais area (northernmost France). The carbonate beds yield field evidences of an early diagenetic origin and both beds and interbeds contain glauconite, questioning the duration of formation of the glauconite, relative to that of the diagenetic carbonate beds. Carbon and oxygen stable isotope composition of the carbonate beds confirm an early diagenetic growth. Contrasted grain-size distribution patterns of glauconite and quartz grain populations (isolated after acid digestion and magnetic separation) evidenced that glauconite formed after sediment deposition. Glauconite formation allegedly requires protracted episodes of ion capture from the water column, which is no longer possible when glauconite gets trapped within authigenic carbonates. Therefore, in-situ glauconite formation preceded carbonate authigenesis. Yet, the chemical composition of grains (Fe and K) typifies glauconite as highly evolved, meaning that its formation must have lasted over times, according to conventional views. Consequently, our results challenge these conventional views and confirm that glauconite can form in relatively shallow environments (which has been already brought to light previously) and it is concluded that early diagenetic glauconite can be markedly enriched in both K and Fe, which is an unprecedented result.

Objectives: To prospectively describe the impact of gas flow rate and temperature on dog's tolerance of high‐flow nasal oxygen therapy during recovery from anaesthesia, hypothesizing that higher flow rates and temperatures will decrease tolerance. Materials and Methods: Twelve non‐dyspnoeic client‐owned dogs recovering from general anaesthesia were included in this study. After extubation, a nasal cannula was positioned and high‐flow nasal oxygen therapy was initiated. Two flow rates (two or four time the theoretical minute ventilation: HF2 and HF4), each of them combined with two temperatures (31 and 37°C: T31 and T37), were randomly applied (four conditions per dog). For each condition, cardiovascular and respiratory parameters (heart rate, respiratory rate, systolic arterial blood pressure and pulse oximeter oxygen saturation), sedation score and tolerance score were recorded at initiation (T0) and after 10 minutes of accommodation (T10). Results: Sedation scores were not significantly different between the four conditions. Cardiovascular and respiratory parameters were not significantly different between any condition at both T0 and T10. Tolerance scores were good and not significantly different between any flow rate or temperature (HF2‐T31: 4 (2‐4), HF4‐T31: 4 (2‐4), HF2‐T37: 4 (2‐4), HF4‐T37: 4 (1‐4)). Clinical Significance: The gas flow rates and temperatures studied have no impact on tolerance during the recovery period of non‐dyspnoeic dogs, and high‐flow nasal cannula is well tolerated. Further studies are required to confirm these results in dyspnoeic dogs. [ABSTRACT FROM AUTHOR]

We characterised the organic matter content of marine deposits at the Oxfordian–Kimmeridgian transition in the Boulonnais (France). Organic rich deposits in platform environments are evidenced in the uppermost Cymodoce and lowermost Mutabilis Zone (early late Kimmeridgian), associated with enhanced planktonic palaeoproductivity and/or developing dysoxia/anoxia. Similar organic rich intervals in early late Kimmeridgian are also evidenced in platform deposits in Normandy and Charentes in France, and in basinal deposits from Yorkshire and Dorset in UK. This refined onset of the organic rich bands (ORB), as described in NW Europe during the late Jurassic, is coeval with seawater warming. We propose that this seawater warming was an important trigger of the onset of the late Jurassic ORB deposition system in NW Europe, which began at the Cymodoce–Mutabilis boundary during the early late Kimmeridgian and lasted until the middle part of the Tithonian, over a time span of 6.8 Myr.