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Pulses of enhanced continental weathering associated with multiple Late Devonian climate perturbations: Evidence from osmium-isotope compositions
Percival, L.M.E.; Selby, D.; Bond, D.P.G.; Rakocinski, M.; Racki, G.; Marynowski, L.; Adatte, T.; Spangenberg, J.E.; Follmi, K.B. (2019). Pulses of enhanced continental weathering associated with multiple Late Devonian climate perturbations: Evidence from osmium-isotope compositions. Palaeogeogr. Palaeoclimatol. Palaeoecol. 524: 240-249. https://hdl.handle.net/10.1016/j.palaeo.2019.03.036
In: Palaeogeography, Palaeoclimatology, Palaeoecology. Elsevier: Amsterdam; Tokyo; Oxford; New York. ISSN 0031-0182; e-ISSN 1872-616X
|  |
| Author keywords |
Frasnian-Famennian extinction; Kellwasser horizons; Annulata event; Nutrient runoff; Marine anoxia; Kowala quarry |
| Auteurs | | Top |
- Percival, L.M.E.
- Selby, D.
- Bond, D.P.G.
|
- Rakocinski, M.
- Racki, G.
- Marynowski, L.
|
- Adatte, T.
- Spangenberg, J.E.
- Follmi, K.B.
|
| Abstract |
Anomalously high rates of continental weathering have frequently been proposed as a key stimulus for the development of widespread marine anoxia during a number of Late Devonian environmental and biospheric crises, which included a major mass extinction during the Frasnian-Famennian transition (marked by the Upper and Lower Kellwasser horizons). Here, this model is investigated by presenting the first stratigraphic record of osmium-isotope trends (Os-187/Os-188) in upper Devonian strata from the Kowala Quarry (Holy Cross Mountains, Poland). Changes in reconstructed Os-187/Os-188 seawater values to more radiogenic compositions are documented at the base of both the Lower (similar to 0.42 to similar to 0.83) and Upper (similar to 0.31 to similar to 0.81) Kellwasser horizons characteristic of the Frasnian-Famennian transition, and additionally within upper Famennian shales that record a more minor environmental perturbation known as the Annulata Event (similar to 0.20 to similar to 0.53). These shifts indicate the occurrence of extremely enhanced continental weathering rates at the onsets of the Kellwasser crises and during the later Annulata Event. The similarity of Os-187/Os-188 values in this study from Frasnian-Famennian boundary and lower Famennian strata (between 0.4 and 0.5) to those from North American stratigraphic equivalents suggests that the Os-187/Os-188 values record global trends. These findings support a causal relationship between increased continental weathering (and thus, nutrient supply to the marine shelf) and the environmental perturbations that occurred during numerous Late Devonian events, including both of the biospherically catastrophic Kellwasser crises as well as other, less severe, oceanic anoxic events. |
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