首页|Osmium and lithium isotope evidence for weathering feedbacks linked to orbitally paced organic carbon burial and Silurian glaciations
Osmium and lithium isotope evidence for weathering feedbacks linked to orbitally paced organic carbon burial and Silurian glaciations
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NSTL
Elsevier
The Ordovician (similar to 487 to 443 Ma) ended with the formation of extensive Southern Hemisphere ice sheets, known as the Hirnantian glaciation, and the second largest mass extinction in Earth History. It was followed by the Silurian (similar to 443 to 419 Ma), one of the most climatically unstable periods of the Phanerozoic as evidenced by several large scale (> 5 parts per thousand) carbon isotope (delta C-13) perturbations associated with further extinction events. Despite several decades of research, the cause of these environmental instabilities remains enigmatic. Here, we provide osmium (Os-187/Os-188) and lithium (delta Li-7) isotope measurements of marine sedimentary rocks that cover four Silurian delta C-13 excursions. Osmium and Li isotope records resemble those previously recorded for the Hirnantian glaciation suggesting a similar causal mechanism. When combined with a new dynamic carbon-osmium-lithium biogeochemical model we suggest that astronomical forcing of the marine organic carbon cycle, as opposed to a decline in volcanic arc degassing or the rise of early land plants, resulted in drawdown of atmospheric CO2, triggering continental scale glaciation, intense global cooling and eustatic sea-level lows recognised in the geological record. Lower atmospheric pCO(2) and temperatures during the Hirnantian and Silurian glaciations suppressed CO2 removal by silicate weathering, driving Os-187/Os-188 and delta Li-7 variability, supporting the existence of climate-regulating feedbacks. (C) 2021 Elsevier B.V. All rights reserved.
osmium (Os-187/Os-188) and lithium (delta Li-7)isotopesSilurian palaeoclimateHirnantian glaciationorbital obliquityeccentricity and precessionsilicate weatheringMASS-SPECTROMETRYGOTLANDEVENTMODEL
Sproson, Adam D.、von Strandmann, Philip A. E. Pogge、Selby, David、Jarochowska, Emilia、Fryda, Jiri、Hladil, Jindrich、Loydell, David K.、Slavik, Ladislav、Calner, Mikael、Maier, Georg、Munnecke, Axel、Lenton, Timothy M.
NSTL
Elsevier
