Anchoring the Late Devonian mass extinction in absolute time by integrating climatic controls and radio-isotopic dating

Abstract

The Devonian Frasnian-Famennian (F-F) boundary marks one of the five main extinction intervals of the phanerozoic Aeon. this time was characterized by two pulses of oceanic anoxia, named the Lower and Upper Kellwasser events, during which massive marine biodiversity losses occurred. this paper presents high-resolution magnetic susceptibility, X-ray fluorescence elemental geochemistry and carbon isotope datasets obtained from the Steinbruch Schmidt f-f boundary section (Germany). these records lead to an astronomical time calibration of the environmental changes associated with the two ocean anoxia pulses. cyclostratigraphic interpretation indicates deposition of the black argillaceous Lower and Upper Kellwasser horizons over ~ 90 and ~ 110 kyr, respectively; approximately equivalent to the duration of one short eccentricity cycle. This study confirms that the succession of events within the Upper Kellwasser event is paced by obliquity, under a loweccentricity orbit. Hence, astronomical insolation forcing likely contributed to the expansion of ocean anoxia and other environmental perturbations associated with these two crises. The new floating chronology established for the Steinbruch Schmidt section is anchored in numerical time by means of a radio-isotopic date, obtained from a bentonite layer interbedded between the two Kellwasser horizons. After anchoring, this time scale gives a high-precision age of 371.870 ± 0.108 Ma for the F-F boundary.

Combined Nitrogen‐Isotope and Cyclostratigraphy Evidence for Temporal and Spatial Variability in Frasnian–Famennian Environmental Change

“…The thin black line indicates the FF boundary; the shaded gray area marks the timing of the early part of the Upper Kellwasser (UKW) Event prior to the end of the Frasnian Stage (De Vleeschouwer et al., 2017). For the H‐32 core, Kowala, and Fuhe, the estimated time in kyr between the onset of local nitrogen‐cycle disturbance and the global carbon‐cycle perturbation is indicated, based on the cyclostratigraphic age models for each record (De Vleeschouwer et al., 2013, 2017; Da Silva et al., 2020; this study ).…”

“…By contrast, the absence of such a clear peak in P tot or P tot /Al values in Frasnian-Famennian strata of the H-32 core indicates minimal change in the influx of this macronutrient to the Illinois Basin at the onset of the UKW et al, 2017). For the H-32 core, Kowala, and Fuhe, the estimated time in kyr between the onset of local nitrogen-cycle disturbance and the global carbon-cycle perturbation is indicated, based on the cyclostratigraphic age models for each record (De Vleeschouwer et al, 2013, 2017Da Silva et al, 2020;this study).…”

“…This chemostratigraphic adjustment is detailed in Table S1 in Supporting Information : the carbon‐isotope‐based tie‐point immediately below the UKW excursion was originally placed at 8.19 m in Da Silva et al. (2020) and De Vleeschouwer et al. (2017), but because the base of the δ 13 C org shift has been revised stratigraphically down‐core, the anchor point has likewise been placed 55 cm deeper than in the previous two studies (at 7.64 m).…”

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

“…A tuffaceous layer just above the F-F boundary from the basinal facies successions in South China yielded a SIMS zircon U-Pb age of 367.8 Ma (Zhang et al, 2020), which correlates with the precise F-F boundary age of ca. 372 Ma from Germany (Percival et al, 2018a;Da Silva et al, 2020). 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).…”

“…Impacts of these events were more severe in low-latitude areas and marine ecosystems, where a fatal impact was caused on shallow-water reefs and fish (McGhee and Racki, 2021). The Late Devonian Viluy LIP (Ricci et al, 2013) in Siberia and the Kola and Pripyat-Dnieper-Donets LIPs (Puchkov et al, 2016) in Baltica are temporally overlapped with the time of Devonian F-F boundary age (Percival et al, 2018a;Da Silva et al, 2020). Climate change, ocean anoxia, and other factors are proposed in concert as the killing mechanisms during these biotic crises (McGhee and Racki, 2021, and references therein), but the ultimate cause of the Late Devonian F-F mass extinction remains somewhat uncertain.…”