Astronomically paced climate and carbon cycle feedbacks in the lead-up to the Late Devonian Kellwasser Crisis
- Autor(en)
- Nina M.A. Wichern, Or M. Bialik, Theresa Nohl, Lawrence M.E. Percival, R. Thomas Becker, Pim Kaskes, Philippe Claeys, David De Vleeschouwer
- Abstrakt
Repeated carbon isotope excursions and widespread organic-rich shale deposition mark the Middle and Upper Devonian series. Various explanations such as extensive volcanism and land plant evolution have been given for these perturbations and the general sensitivity of the Devonian oceans to the development of anoxia, but their repeated nature suggests that astronomical forcing may have controlled their timing. Here, a cyclostratigraphic study of the Kellwasser Crisis at the Frasnian-Famennian stage boundary (ca. 372Ma) is carried out. The Kellwasser Crisis was one of the most ecologically impactful of the Devonian perturbations and is ranked among the "Big Five"Phanerozoic mass extinctions. The studied site is the Winsenberg roadcut section in the Rhenish Massif, Germany, which represents a quiet tropical shelf basin setting. Centimetre-scale elemental records, generated by portable X-ray scanning, allow for testing of the hypothesis that a 2.4Myr eccentricity node preceded the Upper Kellwasser event. The study's results are supportive of this hypothesis. We find enhanced chemical weathering (K2O/Al2O3) during the period leading up to the Upper Kellwasser and a peak in distal detrital input (SiO2/CaO) and riverine runoff (TiO2/Al2O3) just prior to the start of the Upper Kellwasser event. We interpret this pattern as the long-term eccentricity minimum facilitating excessive regolith build-up in the absence of strong seasonal contrasts. The Earth's system coming out of this node would have rapidly intensified the hydrological cycle, causing these nutrient-rich regoliths to be eroded and washed away to the oceans, where they resulted in eutrophication and anoxia. An astronomical control on regional climate is observed beyond this single crisis. Wet-dry cycles were paced by 405kyr eccentricity, with both the Lower and Upper Kellwasser events taking place during comparatively drier times. A precession-sensitive monsoonal climate system prevailed on shorter timescales. Intensification of this monsoonal system following the node may have caused the widespread regolith erosion. We estimate the total duration of the Kellwasser Crisis at ca. 900kyr, with the individual events lasting for ca. 250 and 100kyr, respectively. If astronomical control indeed operated via regolith development in monsoonal climates, then land plants may have played an important role. This would not have been through evolutionary steps directly triggering Kellwasser perturbations but by gradually strengthening the climatic response to orbital forcing via soil development - creating soils thick enough to meaningfully respond to orbital forcing - and intensifying the hydrological cycle.
- Organisation(en)
- Institut für Paläontologie
- Externe Organisation(en)
- Universität Münster, Vrije Universiteit Brussel, Vrije Universiteit Amsterdam, Université Libre de Bruxelles
- Journal
- Climate of the Past
- Band
- 20
- Seiten
- 415-448
- Anzahl der Seiten
- 34
- ISSN
- 1814-9324
- DOI
- https://doi.org/10.5194/cp-20-415-2024
- Publikationsdatum
- 02-2024
- Peer-reviewed
- Ja
- ÖFOS 2012
- 105118 Paläontologie
- ASJC Scopus Sachgebiete
- Global and Planetary Change, Stratigraphy, Palaeontology
- Sustainable Development Goals
- SDG 13 – Maßnahmen zum Klimaschutz, SDG 14 – Leben unter Wasser
- Link zum Portal
- https://ucrisportal.univie.ac.at/de/publications/3cb348df-dc7e-41ce-b307-83ebffd6b0a6