Photic-zone euxinia and anoxic events in a Middle-Late Devonian shelfal sea of Panthalassan continental margin, NW Canada: Changing paradigm of Devonian ocean and sea level fluctuations

Kabanov, Pavel

doi:10.1016/j.gloplacha.2020.103153

Cited by 27 publications

(9 citation statements)

References 116 publications

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“…4 ). This is best explained in terms of the position of a generalized ferruginous-euxinic chemocline, perhaps near the top of one or more thick oxygen minimum zones ( 87 ). Chemocline shoaling and retreat initiated immediately before the Givetian-Frasnian crisis and at ca.…”

Section: Resultsmentioning

confidence: 99%

“…This pattern is consistent with only the Frasnian-Famennian crisis being linked to spatially extensive and fully fledged euxinia (e.g., type 3 pyrite; Figs. 4 to 6 ) ( 2 , 87 ). Disappearance of type 5 pyrite and emergence of type 1 pyrite in the midst of the crisis does not imply that the system was not POM-driven but favors decoupling of the loci of syngenetic pyrite precipitation and POM degradation under highly productive conditions.…”

Section: Resultsmentioning

confidence: 99%

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Pyrite mega-analysis reveals modes of anoxia through geological time

et al. 2022

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The redox structure of the water column in anoxic basins through geological time remains poorly resolved despite its importance to biological evolution/extinction and biogeochemical cycling. Here, we provide a temporal record of bottom and pore water redox conditions by analyzing the temporal distribution and chemistry of sedimentary pyrite. We combine machine-reading techniques, applied over a large library of published literature, with statistical analysis of element concentrations in databases of sedimentary pyrite and bulk sedimentary rocks to generate a scaled analysis spanning the majority of Earth’s history. This analysis delineates the prevalent anoxic basin states from the Archaean to present day, which are associated with diagnostic combinations of five types of syngenetic pyrite. The underlying driver(s) for the pyrite types are unresolved but plausibly includes the ambient seawater inventory, precipitation kinetics, and the (co)location of organic matter degradation coupled to sulfate reduction, iron (oxyhydr)oxide dissolution, and pyrite precipitation.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Pyrite mega-analysis reveals modes of anoxia through geological time

et al. 2022

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“…379–378 Ma overlaps with the end of rapidly succeeding transgression-regression cycles that commenced at ca. 383 Ma (i.e., “depophase IIb” of Johnson et al 1985 ) in this overall global transgression (Johnson et al 1985 ; Kabanov and Jiang 2020 ). Under greenhouse conditions in the Late Devonian (Fig.…”

Section: Discussionmentioning

confidence: 99%

Metal-rich organic matter and hot continental passive margin: drivers for Devonian copper-cobalt-germanium mineralization in dolomitized reef-bearing carbonate platform

et al. 2022

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The abundance and types of reef-bearing carbonate platforms reflect the evolution of Devonian climate, with conspicuous microbial-algal reefs in the warm Early and Late Devonian and sponge-coral reefs in the cooler Middle Devonian. A dolomitized Wenlock-Lower Devonian microbial-algal reef-bearing carbonate platform hosts epigenetic copper-cobalt-germanium (Cu-Co-Ge) sulfide mineralization at Ruby Creek-Bornite in the Brooks Range, Alaska. Here, we present rhenium-osmium (Re-Os) radiometric ages and molybdenum and sulfur (δ98/95Mo = +2.04 to +5.48‰ and δ34S = −28.5 to −1.8‰) isotope variations for individual Cu-Co-Fe sulfide phases along the paragenetic sequence carrollite-bornite-pyrite. In the context of a hot, extensional passive margin, greenhouse conditions in the Early Devonian favored restriction of platform-top seawater circulation and episodic reflux of oxidized brines during growth of the carbonaceous carbonate platform. Molybdenum and sulfur isotope data signal the stepwise reduction of hot brines carrying Cu during latent reflux and geothermal circulation for at least ca. 15 million years from the Early Devonian until Cu-Co sulfide mineralization ca. 379–378 million years ago (Ma) in the Frasnian, Late Devonian (weighted mean of Re-Os model ages of carrollite at 379 ± 15 Ma [n = 4]; Re-Os isochron age of bornite at 378 ± 15 Ma [n = 6]). On the basis of petrographic relationships between sulfides and solid bitumen, and the Mo and S isotope data for sulfides, we imply that the endowment in critical metals (e.g., Co, Ge, Re) in the Ruby Creek-Bornite deposit is linked to the activity of primary producers that removed trace metals from the warm Early Devonian seawater and concentrated Co, Ge, and Re in algal-bacterial organic matter in carbonate sediments.

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“…The thickness of the Hume Fm has been estimated at 114.3 metres (Gouwy et al, 2021). The Prohibition Creek section was selected for its location in the zone of low thermal maturity where Tmax is within 426-465°C and where organic-matter biomarkers are well preserved (Kabanov and Jiang, 2020). Like the Blankenheim section, the CAI values in Prohibition Creek are very low (1.5-2.0; Gouwy, 2006).…”

Section: Canadamentioning

confidence: 99%

“…There are two major mass extinctions during the Late Devonian, one at the Frasnian-Famennian boundary and one at the Devonian-Carboniferous boundary. Nearly all of the Devonian events are accompanied by black shale deposition with a shallow, often photic-zone chemocline fluctuating in the water column (Kabanov and Jiang, 2020), and the nature and magnitude of sea-level fluctuations during the Devonian is also a matter of debate (Carmichael et al, 2019;Kabanov and Jiang, 2020).…”

Section: Introductionmentioning

confidence: 99%

A Persistent Non-uniformitarian Paleomagnetic Field in the Devonian?

Boon¹,

Biggin²,

Thallner³

et al. 2021

Preprint

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The Devonian, like much of the Paleozoic, has long been a problematic period for paleomagnetism. Devonian paleomagnetic data are generally difficult to interpret and have complex partial or full overprints; problems that arise in data obtained from both sedimentary and igneous rocks. As a result, the reconstruction of tectonic plate motions, performed largely using apparent polar wander paths, has large uncertainty. Similarly, the Devonian geomagnetic polarity time scale is very poorly constrained. Paleointensity studies suggest that the field was much weaker than the modern field, and it has been hypothesised that this was accompanied by many polarity reversals (a hyperreversing field). We sampled middle to upper Devonian sections in Germany, Poland and Canada which show low conodont alteration indices, implying low thermal maturity. We show in this study that there are significant issues with these data, and they are not straightforward to interpret, even though no significant heating and remineralisation was likely to have caused overprinting. We compare our data to other magnetostratigraphic studies from the Devonian and review the polarity pattern as presented in the Geologic Time Scale. Combined with estimates for the strength of the magnetic field during the Devonian, we suggest that the field during the Devonian might have been so weak and in part non-dipolar that obtaining reliable primary paleomagnetic data from Devonian rocks is challenging. Careful examination of all data, no matter how unusual, is the best way to push forward our understanding of the Devonian magnetic field. Paleointensity studies show that the field during the Devonian had a similar low strength to that recently advocated during the Ediacaran. Independent evidence from malformed spores around the Devonian-Carboniferous boundary suggests that the terrestrial extinction connected to the Hangenberg event, was caused by increased UV-B radiation, supporting the weak field hypothesis. A fundamentally weak and possibly non-dipolar field during the Devonian could have been produced, in part, by true polar wander acting to maximise core-mantle heat flow in the equatorial region. It may also have influenced evolution and extinctions in this time period. There is a large-number of paleobiological crises in the Devonian, and we pose the question, did the Earth's magnetic field influence these crises?

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Photic-zone euxinia and anoxic events in a Middle-Late Devonian shelfal sea of Panthalassan continental margin, NW Canada: Changing paradigm of Devonian ocean and sea level fluctuations

Cited by 27 publications

References 116 publications

Pyrite mega-analysis reveals modes of anoxia through geological time

Pyrite mega-analysis reveals modes of anoxia through geological time

Metal-rich organic matter and hot continental passive margin: drivers for Devonian copper-cobalt-germanium mineralization in dolomitized reef-bearing carbonate platform

A Persistent Non-uniformitarian Paleomagnetic Field in the Devonian?

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