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

David De Vleeschouwer,Michael T Whalen,Anne-Christine Da Silva,Philippe Claeys,Daizhao Chen,Zenghui Guo,Matthias Sinnesael,James E Day

doi:10.1038/s41467-017-02407-1

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.

Highlights

The Late Devonian envelops one of Earth’s big five mass extinction events at the Frasnian–Famennian boundary (374 Ma)
Both layers coincide with a positive δ13C excursion, as recognized in North America, Morocco, Europe, Russia, western Australia, and southern China[1,3,4,5,6,7,8,9,10]
The result is a common chronology for all six sections, i.e., a global astrochronology for the Late Devonian

Summary

Introduction

The Late Devonian envelops one of Earth’s big five mass extinction events at the Frasnian–Famennian boundary (374 Ma). We considered the magnetic susceptibility and carbon isotope series of six globally distributed F–F sections (Fig. 1) Two of these sections, Kowala (Poland) and Section C (western Canada), were the subject of previous cyclostratigraphic studies[15,16], yielding orbital chronologies based on 405-kyr long eccentricity cycles. The result is a common chronology for all six sections, i.e., a global astrochronology for the Late Devonian This global chronology provides new insight into the rhythm of environmental change across the F–F transition, and reveals the obliquity signature of the UKW positive δ13C excursion. These results confirm the importance of astronomically forced climate change in pacing the biogeochemical interactions that led to the extinction event

Methods

Results

Conclusion