Annique van der Boon, Brian A. Schubert, William M. Hagopian, Mathew Domeier, A. Hope Jahren
The Devonian was a time of climatic upheaval, with many biotic crises, anoxic events and dramatic climatic changes. It is yet unclear what the controls and triggers were for most of these crises, and our understanding is hampered by poorly constrained paleogeographic reconstructions and the limited number and low-resolution of atmospheric CO 2 records. To improve our understanding of paleogeography, atmospheric CO 2 and climate in the Middle Devonian, we obtained paleomagnetic data and a high-resolution carbon isotope record of Givetian (389–383 Ma) organic-rich terrestrial rocks in Svalbard. The section consists of three intervals, with the top of the section in a ~ 100 m interval that likely covers the Taghanic Crisis. While our paleomagnetic data are unsuccessful, our carbon isotope record reveals a baseline value of −25.9 ± 0.8‰, with several smaller excursions and one larger negative excursion of magnitude ~4.0‰. We correlate this excursion to the Taghanic Crisis based on the available biostratigraphy. We use these data to produce a high-resolution atmospheric CO 2 record based on changes in the δ 13 C value of terrestrial organic matter. We find that atmospheric CO 2 varied significantly on short (<10 5 years) timescales, increasing from 623 ppm (1σ: 473–773 ppm) to 1373 ppm (882–2082 ppm) during the Taghanic Crisis – timescales of rapid CO 2 change that cannot be resolved by existing proxies. These changes in CO 2 are consistent with a 13 C depleted source, such as methane (in contrast to a 13 C enriched volcanic source), as a trigger for Middle Devonian biotic crises and high climate volatility. • First high-resolution CO 2 record for the Taghanic crisis from terrestrial rocks. • High-resolution carbon isotope record reveals a Middle Devonian CO 2 spike. • Atmospheric CO 2 more than doubled to 1373 ppm during the Taghanic crisis. • Methane release is proposed as a trigger for this climate perturbation.