The role of organic carbon in the Southern Uplands-Down-Longford Terrane accretionary prism, Scotland and Ireland

Petroleum Geoscience, Journal Year: 2023, Volume and Issue: 29(3)

Published: June 15, 2023

Carbonaceous shales in the Southern Uplands-Down-Longford Terrane accretionary prism had extremely high potential for hydrocarbon generation Lower Paleozoic. Structural thickening enhanced rapid of oil. Shale horizons are separated by thick turbidites composed low-permeability greywackes, so oil under fluid pressure either pooled along shale bedding surfaces or migrated into fractured greywackes. Pooled became solidified to bitumen, which locally formed deposits on a scale tonnes, mined as coal. The carbon-rich also sequestered large amounts sulfur from seawater, precipitated pyrite firstly during early diagenesis, then further flow through beds. was sulfur-bearing. Deformation focused beds evolution would have been closely related bitumen and sulfides. palaeo-fluids were anomalously rich methane hydrogen, similar fluids venting modern prisms. Supplementary material: details localities searched coal Palaeozoic, (locations shown Fig. 6 ) available at https://doi.org/10.6084/m9.figshare.c.6691597

Language: Английский

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Dynamic oceanic redox conditions across the late Cambrian SPICE event constrained by molybdenum and uranium isotopes

Earth and Planetary Science Letters, Journal Year: 2023, Volume and Issue: 604, P. 118013 - 118013

Published: Feb. 1, 2023

The Steptoean Positive Carbon Isotope Excursion Event (SPICE) represents one of the largest carbon cycle perturbations in Cambrian, which coincided with climatic changes and dramatic extinction shallow-shelf faunas. This perturbation has been linked to a global expansion marine euxinia (SPICE-OAE), but precise timing, duration extent changing redox conditions across SPICE event, as well its influences on coeval biotic evolution, remain unclear. Here, we report paired δ98Mo–δ238U data this constrained by radioisotopically anchored astrochronology, based Alum Shale samples from Albjära-1 Billegrav-2 drill-cores Scandinavia. δ98Mo profiles are largely invariant around 1.08±0.21‰ short-term fluctuations parallelling pyritization iron, possibly result locally varying [H2S]aq water column and/or fluctuating reactive iron delivery. bottom is interpreted have primarily anoxic, frequent local variations between oxic sulfidic moderately restricted basin. A novel analytic method variation Mo concentrations at millimeter scale stratigraphic resolution was applied distinguish signatures, revealing that cyclic recorded sea periods ∼0.3 Myr, ∼0.9 Myr ∼0.15 before, during after SPICE-OAE, respectively. Stratigraphic Mo, U, Mo/TOC ratios δ238U two cores show comparable trends, facilitating recognition three chemically distinct stages event: 1) (SPICE-OAE; 497.9–496.6 Ma), 2) contraction accompanied enhanced carbonate weathering inputs (496.6–495.8 Ma) 3) general oxygenation (495.8–494.4 Ma). first situ correlation onset SPICE-OAE end-Miaolingian extinctions Baltica corroborates expansive anoxic masses likely contributed crisis. time gap start appearance new fauna Baltoscandia estimated be ∼600 kyr.

Language: Английский

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Decreased marine organic carbon burial during the Hirnantian glaciation

Earth and Planetary Science Letters, Journal Year: 2025, Volume and Issue: 654, P. 119240 - 119240

Published: Jan. 30, 2025

Language: Английский

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Oceanic anoxia and extinction in the latest Ordovician

Earth and Planetary Science Letters, Journal Year: 2022, Volume and Issue: 588, P. 117553 - 117553

Published: May 9, 2022

Language: Английский

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Molybdenum isotope-based redox deviation driven by continental margin euxinia during the early Cambrian

Geochimica et Cosmochimica Acta, Journal Year: 2022, Volume and Issue: 325, P. 152 - 169

Published: March 9, 2022

Language: Английский

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Geochemical Records Reveal Protracted and Differential Marine Redox Change Associated With Late Ordovician Climate and Mass Extinctions

AGU Advances, Journal Year: 2022, Volume and Issue: 3(1)

Published: Jan. 10, 2022

Abstract The Ordovician (Hirnantian; 445 Ma) hosts the second most severe mass extinction in Earth history, coinciding with Gondwanan glaciation and increased geochemical evidence for marine anoxia. It remains unclear whether cooling, expanded oxygen deficiency, or a combination drove Late Mass Extinction (LOME). Here, we present combined iodine sulfur isotope data from three globally distributed carbonate successions to constrain changes local global redox conditions. Iodine records suggest locally anoxic conditions were potentially pervasive on shallow shelves, while isotopes reduction euxinic (anoxic sulfidic) Katian sulfate‐sulfur show large negative excursion that initiated during elevated sea level continued through peak Hirnantian glaciation. Geochemical box modeling suggests of decreasing pyrite burial increasing weathering are required drive observed suggesting ∼3% decrease seafloor euxinia Ordovician. datasets provide further this trend was followed by increases which coincided eustatic sea‐level rise subsequent deglaciation late Hirnantian. A persistence shelf anoxia against backdrop waning then waxing linked two LOME pulses. These results place important constraints throughout non‐sulfidic shelfal anoxia—along glacioeustatic climatic cooling—were environmental stressors worsened fauna, resulting second‐largest history only example an icehouse climate.

Language: Английский

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Revisiting paleoenvironmental changes on the Upper Yangtze Block during the Ordovician-Silurian transition: New insights from elemental geochemistry

Sedimentary Geology, Journal Year: 2023, Volume and Issue: 450, P. 106377 - 106377

Published: April 4, 2023

Language: Английский

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Was the Late Ordovician mass extinction truly exceptional?

Trends in Ecology & Evolution, Journal Year: 2023, Volume and Issue: 38(9), P. 812 - 821

Published: May 12, 2023

Language: Английский

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Reviews and syntheses: Review of proxies for low-oxygen paleoceanographic reconstructions

Published: Jan. 9, 2024

Abstract. A growing body of observations reveals rapid changes in both the total inventory and distribution marine oxygen over later half 21st century, leading to increased interest extending oxygenation records into past. Use paleo-oxygen proxies have potential extend spatial temporal range current records, bound pre-anthropogenic baselines, provide datasets necessary test climate models under different boundary conditions, ultimately understand how ocean responds beyond decadal scale changes. This review seeks summarize state-of-knowledge about for reconstructing Cenozoic oxygen: sedimentary features, redox-sensitive trace elements isotopes, biomarkers, nitrogen foraminiferal elements, foraminifera assemblages, morphometrics, benthic carbon isotope gradients. Taking stock each proxy some common limitations that majority function best at low-oxygen concentrations many reflect multiple environmental drivers. We also highlight recent breakthroughs geochemistry approaches constraining pelagic (in addition benthic) are rapidly advancing field. In light emergence new persistent driver problem, need multi-proxy FAIR data storage sharing is emphasized. Continued refinement proxy-proxy proxy-model comparisons likely support needs oceanographer paleoceanographers interested paleo-oxygenation records.

Language: Английский

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Productivity and organic carbon loading control uranium isotope behavior in ancient reducing settings: Implications for the paleoredox proxy

Geochimica et Cosmochimica Acta, Journal Year: 2024, Volume and Issue: 368, P. 197 - 213

Published: Jan. 13, 2024

Language: Английский

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