Journal cover Journal topic
Climate of the Past An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/cp-2017-136
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
25 Oct 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Climate of the Past (CP).
Salinity changes and anoxia resulting from enhanced runoff during the late Permian global warming and mass extinction event
Elsbeth E. van Soelen1, Richard J. Twitchett2, and Wolfram M. Kürschner3 1University of Oslo, Departments of Geosciences, P.O. box 1047 Blindern 0316 Oslo, Norway
2Natural History Museum, Earth Sciences Department, London, SW7 5BD, UK
3Department of Geosciences and Centre for Earth Evolution and Dynamics (CEED), University of Oslo, Oslo, Norway
Abstract. The Late Permian biotic crisis had a major impact on marine and terrestrial environments. Rising CO2 levels following Siberian Trap volcanic activity were likely responsible for expanding marine anoxia and elevated water temperatures. This study focusses on one of the stratigraphically most expanded Permian-Triassic records known, from Jameson land, east Greenland. High resolution sampling allows for a detailed reconstruction of the changing environmental conditions during the extinction event and the development of anoxic water conditions. Since very little is known about how salinity was affected during the extinction event, we especially focus on the aquatic palynomorphs and infer changes in salinity from changes in the assemblage and morphology. The extinction event, here defined by a peak in spore/pollen, indicating disturbance and vegetation destruction in the terrestrial environment, postdates a negative excursion in the total organic carbon, but predates the development of anoxia in the basin. Based on the newest estimations for sedimentation rates, the marine and terrestrial ecosystem collapse took between 1.6 to 8 kyrs, a much shorter interval than previously estimated. The palynofacies and palynomorph records show that the environmental changes can be explained by enhanced runoff, increased primary productivity and water column stratification. A lowering in salinity is supported by changes in the acritarch morphology. The length of the processes of the acritarchs becomes shorter during the extinction event and we propose that these changes are evidence for a reduction in salinity in the shallow marine setting of the study site. This inference is supported by changes in acritarch distribution, which suggest a change in palaeoenvironment from open marine conditions before the start of the extinction event to more near-shore conditions during and after the crisis. In a period of sea-level rise, such a reduction in salinity can only be explained by increased runoff. High amounts of both terrestrial and marine organic fragments in the first anoxic layers suggest that high runoff, increased nutrient availability, possibly in combination with soil erosion, are responsible for the development of anoxia in the basin. Enhanced runoff could result from changes in the hydrological cycle during the late Permian extinction event, which is a likely consequence of global warming. In addition, vegetation destruction and soil erosion may also have resulted in enhanced runoff. Salinity stratification could potentially explain the development of anoxia in other shallow marine sites. The input of fresh water and related changes in coastal salinity could also have implications for the interpretation of oxygen isotope records and sea water temperature reconstructions in some sites.

Citation: van Soelen, E. E., Twitchett, R. J., and Kürschner, W. M.: Salinity changes and anoxia resulting from enhanced runoff during the late Permian global warming and mass extinction event, Clim. Past Discuss., https://doi.org/10.5194/cp-2017-136, in review, 2017.
Elsbeth E. van Soelen et al.
Elsbeth E. van Soelen et al.
Elsbeth E. van Soelen et al.

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