Zechstein saline brines in Poland, evidence of overturned anoxic ocean during the late Permian mass extinction event
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Date
2011-11-24
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Elsevier
Abstract
Bromine concentrations in halite, sulfate isotopes (delta S-34 and delta O-18), and major ion concentrations in primary fluid inclusions from three boreholes in the Late Permian Zechstein evaporites have revealed sharp variations in marine derived brines within the Polish sector of the European Southern Permian Basin. The base of the Older Halite (Na2), during the latest Permian, registers a change from sulfate-rich brines, similar in composition to modern evaporated seawater, to sulfate-depleted brines (calcium-rich). This change coincides with a drop in delta S-34 to values close to +9 parts per thousand, not observed in delta O-18 counterparts. Opposite isotope (delta S-34-delta O-18) trends through the Na2 unit cannot be explained by changes in restriction conditions. We propose that the change to sulfate-depleted (calcium-rich) brines during halite deposition of the PZ2 (Stassfurt) cycle is related to the overturn of anoxic sulfidic deep-waters from the Panthalassa stratified superocean coinciding in time with the Permian-Triassic mass extinction event.
The reconstruction of chemical changes in brines reveals two major evaporite sequences of increasing concentration that do not match the classic lithostratigraphic cycles. The first evaporite sequence (PZES-1) contain the evaporite units of the PZ1 (Werra) cycle, the PZ2 (Stassfurt) cycle, the Main Anhydrite (A3), and the base of the Younger Halite (Na3) of the PZ3 (Leine) cycle. The second evaporite sequence (PZES-2) is represented by almost the entire Na3 unit and the PZ4 (Aller) cycle. (C) 2011 Elsevier B.V.
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Sulfates, Brines, Evaporites, Paleozoic Era, Seas, Poland
Citation
García-Veigas, J., Cendón, D. I., Pueyo, J. J., Peryt, T. M. (2011). Zechstein saline brines in Poland, evidence of overturned anoxic ocean during the late Permian mass extinction event. Chemical Geology, 290(3-4), 189-201. doi:10.1016/j.chemgeo.2011.09.016