Late Ordovician mass extinction caused by global warming or cooling?
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PERSPECTIVE
Late Ordovician mass extinction caused by global warming or cooling? Renqiang Liao1,2
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Weidong Sun1,2,3
Received: 31 July 2020 / Revised: 31 July 2020 / Accepted: 18 August 2020 Ó Science Press and Institute of Geochemistry, CAS and Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The Late Ordovician mass extinction (LOME) was the first global extinction with the destruction of 85 % of marine species. However, the cause of LOME is still controversial. Most studies attribute it to large-scale volcanism caused by global cooling or warming. Through analyzing the driving difference between global cooling and warming on large-scale magmatism, the perspective is intended to evoke a hot discussion on the cause of LOME. Did global cooling or warming trigger the LOME? Keywords Late Ordovician Mass extinction Volcanism Glaciation There have been ‘‘Big Five’’ extinctions on Earth since the Phanerozoic Era. The Late Ordovician mass extinction (LOME) was the first global mass extinction, which ranks second among the five mass extinctions, with the destruction of 85 % of marine species (e.g., Sheehan 2001). Previous studies suggested that the majority of extinction events are temporally related to large igneous provinces (e.g., Courtillot and Olson 2007). However, the cause of LOME is still controversial, with models ranging from glaciation (Ling et al. 2019; Trotter et al. 2008),
& Weidong Sun [email protected] 1
Institute of Oceanology, Center for Ocean Mega-Science, Center of Deep Sea Research, Chinese Academy of Sciences, Qingdao 266071, China
2
University of Chinese Academy of Sciences, Beijing 100049, China
3
Laboratory for Marine Mineral Resources, Pilot National Laboratory for Marine Science and Technology, Qingdao 266237, China
environmental perturbations (Algeo et al. 2016), oceanic redox changes (Hammarlund et al. 2012), large-scale volcanism (Grasby et al. 2019; Jones et al. 2017), or multifactors co-evolution (Harper et al. 2014). Recently, Bond and Grasby (2020) analyzed Hg contents and other biogeochemical indicators (e.g., Mo, U, TOC, Zn) of a set of Ordovician–Silurian deep-water sediments exposed at Dob’s Linn (Scotland). Based on these data, they suggested that LOME was driven by global warming caused by large-scale volcanism. This challenges previous models that LOME was the result of global cooling and fast glaciation based on oxygen isotopes (e.g., Trotter et al. 2008) and high precision U–Pb dating results (Ling et al. 2019). The use of mercury (Hg) as an indicator of ancient volcanoes in sediments has arisen in the past decade, which was taken as key evidence for solving this issue (Grasby et al. 2019). Before human activities, Mercury is mainly released from volcanoes or hydrothermal fluids (Pyle and Mather 2003). Hg has a long residence time of * 0.5 to 1 year in the atmosphere, allowing long-distance transport, dispersal, and mixing (Selin 2009). Meanwhile, Hg has a relatively short residence time in the ocean (* 102 to 103 year), such that the sign
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