Significant Fluctuation in the Global Sulfate Reservoir and Oceanic Redox State During the Late Devonian Mass Extinction

Abstract

Sulfate plays an important role in the biosphere, hydrosphere, atmosphere, and lithosphere, and its concentration might have fluctuated greatly throughout the Earth’s history, in response to perturbations in the ocean-atmosphere system. Coupling high-resolution experimental results with an inverse modeling approach, we, here, show an unprecedented dynamic in the global sulfate reservoir during the Frasnian-Famennian (F-F) mass extinction, as one of the “Big five” Phanerozoic biotic crises. Notably, our results indicate that, in a relatively short time scale (~ 200 thousand years), seawater sulfate concentration would have dropped from several mM before the Upper Kellwasser Horizon (UKH) to a few hundreds of µM or perhaps lower at the dawn and during the UKH (more than 100 times lower than the modern level), and returned to around mM range after the event. The extremely low oceanic sulfate concentrations during the UKH would have enhanced the biological production of methane, leading to an increase in the methane efflux from the ocean and a warmer climate. Taken together, our findings indicate that the instability in the global sulfate reservoir may have played a major role in driving the Phanerozoic biological crises.

Mercury Anomalies Link to Extensive Volcanism Across the Late Devonian Frasnian–Famennian Boundary in South China

“…Low redox sensitive element concentrations (Mo, U, V) and low V/Cr ratios (<2) suggest a constant oxic ocean condition in South China during the F-F transition (Zhang et al, 2020). Ocean sulfate deficit (Cai et al, 2020), climate change (Huang et al, 2018), tectonic evolution, and volcanic/hydrothermal activities (Ma et al, 2016;Zhang et al, 2020) have been proposed as the killing mechanisms for F-F mass extinction in South China.…”

“…The Late Devonian Frasnian-Famennian (F-F) transition witnessed one of the "Big Five" mass extinctions which killed at least 40% of all species during the Phanerozoic (e.g., Stanley, 2016). This critical period was characterized by many global events including climate oscillations (Huang et al, 2018;Liu et al, 2020), eustatic sea-level changes (Sandberg et al, 2002;Bond and Wignall, 2008), atmospheric O 2 fluctuation (Dahl et al, 2010), seawater anoxic/hypoxic events (Kellwasser events, Joachimski and Buggisch, 1993), eutrophication events (Murphy et al, 2000), and instability in the sulfate reservoir (Cai et al, 2020). Three main Late Devonian extinction events occurred within an interval of 0.7 Ma from the latest Frasnian to the earliest Famennian stages.…”