Timing and pacing of the Late Devonian mass extinction event regulated by eccentricity and obliquity

Abstract

The Late Devonian envelops one of Earth’s big five mass extinction events at the Frasnian–Famennian boundary (374 Ma). Environmental change across the extinction severely affected Devonian reef-builders, besides many other forms of marine life. Yet, cause-and-effect chains leading to the extinction remain poorly constrained as Late Devonian stratigraphy is poorly resolved, compared to younger cataclysmic intervals. In this study we present a global orbitally calibrated chronology across this momentous interval, applying cyclostratigraphic techniques. Our timescale stipulates that 600 kyr separate the lower and upper Kellwasser positive δ13C excursions. The latter excursion is paced by obliquity and is therein similar to Mesozoic intervals of environmental upheaval, like the Cretaceous Ocean-Anoxic-Event-2 (OAE-2). This obliquity signature implies coincidence with a minimum of the 2.4 Myr eccentricity cycle, during which obliquity prevails over precession, and highlights the decisive role of astronomically forced “Milankovitch” climate change in timing and pacing the Late Devonian mass extinction.

On the Sensitivity of the Devonian Climate to Continental Configuration, Vegetation Cover, Orbital Configuration, CO 2 Concentration, and Insolation

“…This study finds a strong dependence of the Devonian climate on orbital parameters and supports a link between ocean anoxic events during the Devonian and orbital forcing. Using cyclostratigraphic techniques, De Vleeschouwer et al (2017) Except for a small eccentricity offset of the coldest state and a slight dependence on precession, De Vleeschouwer et al (2014) also find that global mean temperature increases with obliquity and eccentricity. However, they report significantly larger temperature variations with orbital parameters.…”

“…This study finds a strong dependence of the Devonian climate on orbital parameters and supports a link between ocean anoxic events during the Devonian and orbital forcing. Using cyclostratigraphic techniques, De Vleeschouwer et al () see the root cause of the Frasnian‐Famennian extinction event in strong perturbations of the carbon cycle (e.g., as an effect of the land plant evolution) but suggest that it is triggered by a particular succession of orbital parameters. This proposed link makes a comparison to the model results of De Vleeschouwer et al () particularly interesting.…”

“…Furthermore, there are several studies stressing the importance of astronomical forcing for the climate during the Devonian. The geologic record of the Devonian shows cyclic structures (De Vleeschouwer et al, , ) which can be interpreted as the result of astronomical cycles according to Milankovitch theory (Milankovitch, ). The configuration of Earth's orbit and rotational axis determines the total amount as well as the spatial and temporal distribution of solar radiation and therefore impacts climate.…”

“…The configuration of Earth's orbit and rotational axis determines the total amount as well as the spatial and temporal distribution of solar radiation and therefore impacts climate. In addition, identifying astronomical cycles in the geologic record can help assign a timescale to cyclic features observed in the geologic record and thus a timescale for palaeoclimatic changes (De Vleeschouwer et al, , , ).…”

Pulses of enhanced continental weathering associated with multiple Late Devonian climate perturbations: Evidence from osmium-isotope compositions

“…Organic-rich shales (interbedded with limestones) are prevalent throughout much of the Kowala stratigraphic sequence, ideal for Re-Os analysis due to the uptake of both Re and Os from seawater into organic muds during deposition (Ravizza and Turekian, 1989;Cohen et al, 1999). The UKW Horizon has been well documented at Kowala on the basis of conodont biostratigraphy (Szulczewski, 1971(Szulczewski, , 1996, an elevated total organic carbon (TOC) content, and a positive carbon-isotope (δ 13 C) excursion of up to 4 ‰ in both carbonates and bulk and compound-specific organic matter (Joachimski et al, 2001), which is characteristic of both Kellwasser events in stratigraphic archives across the globe (e.g., Joachimski and Buggisch, 1993;Chen et al, 2005;De Vleeschouwer et al, 2017). This stratigraphic positioning of the UKW Horizon is supported by several other indications of marine anoxia such as pyrite framboid size populations and trace metal contents (e.g., vanadium/chromium ratios), all of which show perturbations just below the F-F boundary (Joachimski et al, 2001;Racki et al, 2002;Bond et al, 2004).…”