Cover Image Credits

View of the sedimentary record of the Cenomanian–Turonian (Late Cretaceous) Oceanic Anoxic Event 2 (OAE 2) at the abandoned Furlo quarry (Marche, Italy; photo courtesy of Ian Jarvis, 2018), showing geochemical trends that have been used to infer changes to the global carbon cycle (carbon isotopes; Jenkyns and others, 2007) and Large Igneous Province volcanic activity that may have triggered those perturbations (osmium isotopes; Turgeon and Creaser, 2008; and mercury concentrations; this study). Volcanically caused carbon-cycle disturbances have previously been indicated by carbon- and osmium-isotope trends, both at Furlo and in other locations across the world. This study analyzed sedimentary mercury contents as an additional proxy for volcanism in order to further investigate this hypothesis. However, study of eight new OAE 2 records including Furlo highlight that there is no globally distributed enrichment in sedimentary mercury contents suggestive of volcanism that correlates with the osmium signal. A similar discrepancy in osmium and mercury as geochemical proxies of volcanism also appears to be the case in sedimentary records of the Cretaceous–Paleogene interval and mass extinction. It is concluded that there are important complexities inherent in the use of mercury enrichments as a geochemical proxy of volcanism, such as local sedimentological processes (for example, lithological variation, organic matter content and type), and the style of volcanic activity in question (for example, submarine vs subaerial and/or explosive vs effusive eruptions). See paper by Percival and others, p. 799–860.