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Lower Wenlock black shales in the northern Holy Cross Mountains, Poland: Sedimentary and geochemical controls on the Ireviken Event in a deep marine setting

Smolarek, Justyna; Trela, Wies?aw; Bond, David P. G.; Marynowski, Leszek


Justyna Smolarek

Wies?aw Trela

Leszek Marynowski


The stratigraphic variability and geochemistry of Llandovery/Wenlock (L/W) Series boundary sediments in Poland reveals that hemipelagic sedimentation under an anoxic/euxinic water column was interrupted by low density bottom currents or detached diluted turbid layers that resulted in intermittent seafloor oxygenation. TOC values and inorganic proxies throughout the Wilków 1 borehole section suggest variable redox conditions. U/Mo ratios >1 throughout much of the Aeronian and Telychian Stages, together with an absence of pyrite framboids, suggests oxygenated conditions prevailed. However, elevated TOC near the Aeronian/Telychian boundary, together with increased U/Th and V/(V+Ni) ratios and populations of small pyrite framboids are consistent with the development of dysoxic/anoxic conditions at that time. U/Th, V/Cr and V/(V+Ni) ratios, as well as Uauthig and Mo concentrations suggest that during the Ireviken black shale (IBS) deposition, bottom-water conditions deteriorated from oxic during the Telychian to mostly suboxic/anoxic immediately prior to the L/W boundary, before a brief reoxygenation at the end of the IBS sedimentation in the Sheinwoodian Stage. Rapid fluctuations in U/Mo during the Ireviken Event (IE) are characteristic of fluctuating redox conditions that culminated in an anoxic/euxinic seafloor in the Sheinwoodian. Following IBS deposition, conditions once again became oxygen deficient with the development of a euxinic zone in the water column. The Aeronian to Sheinwoodian deep-water redox history was unstable, and rapid fluctuations of the chemocline across the L/W Series boundary probably contributed to the IE extinctions, which affected mainly pelagic and hemipelagic fauna.


Smolarek, J., Trela, W., Bond, D. P. G., & Marynowski, L. (2017). Lower Wenlock black shales in the northern Holy Cross Mountains, Poland: Sedimentary and geochemical controls on the Ireviken Event in a deep marine setting. Geological magazine, 154(2), 247-264.

Journal Article Type Article
Acceptance Date Nov 23, 2015
Online Publication Date Feb 4, 2016
Publication Date Mar 1, 2017
Deposit Date Dec 21, 2015
Publicly Available Date Oct 27, 2022
Journal Geological magazine
Print ISSN 0016-7568
Electronic ISSN 1469-5081
Publisher Cambridge University Press
Peer Reviewed Peer Reviewed
Volume 154
Issue 2
Pages 247-264
Keywords Irevekin Event; Redox conditions; Inorganic proxies; Pyrite framboids; Silurian
Public URL
Publisher URL
Additional Information This is the author's accepted manuscript of an article published in Geological magazine, 2017, v.154 issue 2.


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